Hormonal birth control explainer: a matter of health

Politics often interferes where it has no natural business, and one of those places is the discussion among a teenager, her parents, and her doctor or between a woman and her doctor about the best choices for health. The hottest button politics is pushing right now takes the form of a tiny hormone-containing pill known popularly as the birth control pill or, simply, The Pill. This hormonal medication, when taken correctly (same time every day, every day), does indeed prevent pregnancy. But like just about any other medication, this one has multiple uses, the majority of them unrelated to pregnancy prevention.

But let’s start with pregnancy prevention first and get it out of the way. When I used to ask my students how these hormone pills work, they almost invariably answered, “By making your body think it is pregnant.” That’s not correct. We take advantage of our understanding of how our bodies regulate hormones not to mimic pregnancy, exactly, but instead to flatten out what we usually talk about as a hormone cycle. 

The Menstrual Cycle

In a hormonally cycling girl or woman, the brain talks to the ovaries and the ovaries send messages to the uterus and back to the brain. All this chat takes place via chemicals called hormones. In human females, the ovarian hormones are progesterone and estradiol, a type of estrogen, and the brain hormones are luteinizing hormoneand follicle-stimulating hormone. The levels of these four hormones drive what we think of as the menstrual cycle, which exists to prepare an egg for fertilization and to make the uterine lining ready to receive a fertilized egg, should it arrive. 

Fig. 1. Female reproductive anatomy. Credit: Jeanne Garbarino.
In the theoretical 28-day cycle, fertilization (fusion of sperm and egg), if it occurs, will happen about 14 days in, timed with ovulation, or release of the egg from the ovary into the Fallopian tube or oviduct (see video–watch for the tiny egg–and Figure 1). The fertilized egg will immediately start dividing, and a ball of cells (called a blastocyst) that ultimately develops is expected to arrive at the uterus a few days later.
If the ball of cells shows up and implants in the uterine wall, the ovary continues producing progesterone to keep that fluffy, welcoming uterine lining in place. If nothing shows up, the ovaries drop output of estradiol and progesterone so that the uterus releases its lining of cells (which girls and women recognize as their “period”), and the cycle starts all over again.

A typical cycle

The typical cycle (which almost no girl or woman seems to have) begins on day 1 when a girl or woman starts her “period.” This bleeding is the shedding of the uterine lining, a letting go of tissue because the ovaries have bottomed out production of the hormones that keep the tissue intact. During this time, the brain and ovaries are in communication. In the first two weeks of the cycle, called the “follicular phase” (see Figure 2), an ovary has the job of promoting an egg to mature. The egg is protected inside a follicle that spends about 14 days reaching maturity. During this time, the ovary produces estrogen at increasing levels, which causes thickening of the uterine lining, until the estradiol hits a peak about midway through the cycle. This spike sends a hormone signal to the brain, which responds with a hormone spike of its own.

Fig. 2. Top: Day of cycle and phases. Second row: Body temperature (at waking) through cycle.
Third row: Hormones and their levels. Fourth row: What the ovaries are doing.
Fifth row: What the uterus is doing. Via Wikimedia Commons
In the figure, you can see this spike as the red line indicating luteinizing hormone. A smaller spike of follicle-stimulating hormone (blue line), also from the brain, occurs simultaneously. These two hormones along with the estradiol peak result in the follicle expelling the egg from the ovary into the Fallopian tube, or oviduct (Figure 3, step 4). That’s ovulation.
Fun fact: Right when the estrogen spikes, a woman’s body temperature will typically drop a bit (see “Basal body temperature” in the figure), so many women have used temperature monitoring to know that ovulation is happening. Some women also may experience a phenomenon called mittelschmerz, a pain sensation on the side where ovulation is occurring; ovaries trade off follicle duties with each cycle.  

The window of time for a sperm to meet the egg is usually very short, about a day. Meanwhile, as the purple line in the “hormone level” section of Figure 2 shows, the ovary in question immediately begins pumping out progesterone, which maintains that proliferated uterine lining should a ball of dividing cells show up.
Fig. 3. Follicle cycle in the ovary. Steps 1-3, follicular phase, during
which the follicle matures with the egg inside. Step 4: Ovulation, followed by
the luteal phase. Step 5: Corpus luteum (yellow body) releases progesterone.
Step 6: corpus luteum degrades if no implantation in uterus occurs.
Via Wikimedia Commons.
The structure in the ovary responsible for this phase, the luteal phase, is the corpus luteum (“yellow body”; see Figure 3, step 5), which puts out progesterone for a couple of weeks after ovulation to keep the uterine lining in place. If nothing implants, the corpus luteum degenerates (Figure 3, step 6). If implantation takes place, this structure will (should) instead continue producing progesterone through the early weeks of pregnancy to ensure that the lining doesn’t shed.

How do hormones in a pill stop all of this?

The hormones from the brain–luteinizing hormone and follicle-stimulating hormone– spike because the brain gets signals from the ovarian hormones. When a girl or woman takes the pills, which contain synthetics of ovarian hormones, the hormone dose doesn’t peak that way. Instead, the pills expose the girl or woman to a flat daily dose of hormones (synthetic estradiol and synthetic progesterone) or hormone (synthetic progesterone only). Without these peaks (and valleys), the brain doesn’t release the hormones that trigger follicle maturation or ovulation. Without follicle maturation and ovulation, no egg will be present for fertilization.

Assorted hormonal pills. Via Wikimedia Commons.
Most prescriptions of hormone pills are for packets of 28 pills. Typically, seven of these pills–sometimes fewer–are “dummy pills.” During the time a woman takes these dummy pills, her body shows the signs of withdrawal from the hormones, usually as a fairly light bleeding for those days, known as “withdrawal bleeding.” With the lowest-dose pills, the uterine lining may proliferate very little, so that this bleeding can be quite light compared to what a woman might experience under natural hormone influences.

How important are hormonal interventions for birth control?

Every woman has a story to tell, and the stories about the importance of hormonal birth control are legion. My personal story is this: I have three children. With our last son, I had two transient ischemic attacks at the end of the pregnancy, tiny strokes resulting from high blood pressure in the pregnancy. I had to undergo an immediate induction. This was the second time I’d had this condition, called pre-eclampsia, having also had this with our first son. My OB-GYN told me under no uncertain terms that I could not–should not–get pregnant again, as a pregnancy could be life threatening.

But I’m married, happily. As my sister puts it, my husband and I “like each other.” We had to have a failsafe method of ensuring that I wouldn’t become pregnant and endanger my life. For several years, hormonal medication made that possible. After I began having cluster headaches and high blood pressure on this medication in my forties, my OB-GYN and I talked about options, and we ultimately turned to surgery to prevent pregnancy.

But surgery is almost always not reversible. For a younger woman, it’s not the temporary option that hormonal pills provide. Hormonal interventions also are available in other forms, including as a vaginal ring, intrauterine device (some are hormonal), and implants, all reversible.


One of the most important things a society can do for its own health is to ensure that women in that society have as much control as possible over their reproduction. Thanks to hormonal interventions, although I’ve been capable of childbearing for 30 years, I’ve had only three children in that time. The ability to control my childbearing has meant I’ve been able to focus on being the best woman, mother, friend, and partner I can be, not only for myself and my family, but as a contributor to society, as well.

What are other uses of hormonal interventions?

Heavy, painful, or irregular periods. Did you read that part about how flat hormone inputs can mean less build up of the uterine lining and thus less bleeding and a shorter period? Many girls and women who lack hormonal interventions experience bleeding so heavy that they become anemic. This kind of bleeding can take a girl or woman out of commission for days at a time, in addition to threatening her health. Pain and irregular bleeding also are disabling and negatively affect quality of life on a frequent basis. Taking a single pill each day can make it all better. 

Unfortunately, the current political climate can take this situation–especially for teenage girls–and cast it as a personal moral failing with implications that a girl who takes hormonal medications is a “slut,” rather than the real fact that this hormonal intervention is literally maintaining the regularity of her health.

For some context, imagine that a whenever a boy or man produced sperm, it was painful or caused extensive blood loss that resulted in anemia. Would there be any issues raised with providing a medication that successfully addressed this problem?

Polycystic ovarian syndrome. This syndrome is, at its core, an imbalance of the ovarian hormones that is associated with all kinds of problems, from acne to infertility to overweight to uterine cancer. Guess what balances those hormones back out? Yes. Hormonal medication, otherwise known as The Pill.  

Again, for some context, imagine that this syndrome affected testes instead of ovaries, and caused boys and men to become infertile, experience extreme pain in the testes, gain weight, be at risk for diabetes, and lose their hair. Would there be an issue with providing appropriate hormonal medication to address this problem?

Acne. I had a friend in high school who was on hormonal medication, not because she was sexually active (she was not) but because she struggled for years with acne. This is an FDA-approved use of this medication.

Are there health benefits of hormonal interventions?

In a word, yes. They can protect against certain cancers, including ovarian and endometrial, or uterine, cancer. Women die from these cancers, and this protection is not negligible. They may also help protect against osteoporosis, or bone loss. In cases like mine, they protect against a potentially life-threatening pregnancy.

Speaking of pregnancy, access to contraception is “the only reliable way” to reduce unwanted pregnancies and abortion rates [PDF]. Pregnancy itself is far more threatening to a girl’s (in particular) or woman’s health than hormonal contraception.

Are there health risks with hormonal interventions?

Yes. No medical intervention is without risk. In the case of hormonal interventions, lifestyle habits such as smoking can enhance risk for high blood pressure and blood clots. Age can be a factor, although–as I can attest–women no longer have to stop taking hormonal interventions after age 35 as long as they are nonsmokers and blood pressure is normal. These interventions have been associated with a decrease in some cancers, as I’ve noted, but also with an increase in others, such as liver cancer, over the long term. The effect on breast cancer risk is mixed and may have to do with how long taking the medication delays childbearing. ETA: PLoS Medicine just published a paper (open access) addressing the effects of hormonal interventions on cancer risk.
By Emily Willingham, DXS Managing Editor
Opinions expressed in this piece are my own and do not necessarily reflect the opinions of all DXS editors or contributors.

Pertussis: Get the vax or at least listen to why you should

by Tara Haelle, DXS contributor

The past few weeks have seen big news for vaccines. A bill related to vaccine exemptions was signed into law, a court ruled against a parent’s refusal to vaccinate and a recent study points out the value of vaccinating a household — especially mom — to protect a young infant from pertussis (whooping cough).

The latest news is that Governor Jerry Brown in California signed a bill last Sunday that had been sitting on his desk since September 6 and was the target of a number of rallies by parents who didn’t want to see it pass. Among those fighting the bill was Dr. Bob Sears, who says he walks a middle ground with vaccine policy but in reality tends to flirt with those who fear vaccines and rely on misinformation. Although some parents claimed the bill took away their right to choose whether their children get vaccinated, it actually just ensures they get good medical information before they make that choice.

Photo by Dave Gostisha at sxc.hu.
The bill-now-law, AB 2109, proposed by a pediatrician, requires parents to get a statement signed by a health care practitioner that the parents/guardians have received accurate, evidence-based information about the risks and benefits of vaccines before they can use a personal belief exemption to prevent their children from being vaccinated. This law is a tremendous triumph both for informed consent in medical decisions and for the public health of children in California, which saw a considerable outbreak of pertussis (whooping cough) in 2010. Washington state passed a similar law last year and saw 25 percent drop in exemptions filed. Other states are considering similar laws in a nationwide overall shift toward strengthening exemption requirements.

Why are these laws so important? In short, they kill two birds with one stone: They make it more difficult for parents to casually opt out of vaccines on philosophical grounds (as opposed to religious or medical reasons), and they require parents who want to opt out to at least hear out a pediatrician on accurate information about the actual risks (which do exist) and benefits (there are so many) of immunizations. Parents who are determined not to vaccinate their children can still refuse, but many parents who might have signed those forms out of convenience — it can be easier to sign than to get to the doctor’s office for the shot — will now at least hear the impact a decision not to vaccinate can have on the community. (Hopefully, they go to a health care practitioner other than Dr. Sears, whose stances have gradually been moving further and further toward unscientific and misinformation of those who oppose vaccines.) 

It’s also particularly notable that California and Washington are the most recent states to tighten opt-out procedures for parents because they are home to some of the more recent pertussis outbreaks. More on that in a moment.

First, a bit of background on vaccine exemptions: Only 20 states have personal belief exemptions, and until last year, eight of these simply require nothing more than a parent signature. Now that number is down to six. (Other types of requirements for philosophical exemptions include writing out your reasons for exemption, requiring the forms to be notarized, requiring education on the risks/benefits, direct involvement from the state or local health department or renewals.)

All states have medical exemptions for patients who have auto-immune disorders, have proof that their bodies do not respond to immunization, have documented allergic reactions or have other circumstances which make it too risky for them to be immunized. In fact, these are the very people that the rest of the population protects through herd immunity when vaccination rates are up where they should be. All but two states have religious exemptions (Mississippi and West Virginia are the exceptions).

And that brings us to some less covered but still significant news about one state’s ruling on a particular case involving religious exemption. Last week, the U.S. district court in Ohio ruled that one woman’s claim of religious objection was insufficient for her children to be exempted from being vaccinated. Read the whole story here. To be fair, this is a complex case involving far more than vaccines; the mother is clearly neglectful and the overall situation is pretty crappy. However, the fact that the court found “the mere assertion of a religious belief … does not automatically trigger First Amendment protections,” and that “it has long been recognized that local authorities may constitutionally mandate vaccinations” is significant in a state that offers both religious and personal belief exemptions.

Because of the danger to public health when clusters of kids are not vaccinated, my personal opinion on this issue is that “personal belief” exemptions should not be offered in any state, and religious exemptions should be extremely difficult to get, if they are offered at all (which may be the best overall route). Some cite the Amish, Mennonite and Christian Scientists, though actually the majority of Amish children, at least, are vaccinated, and it doesn’t appear that any Amish objections to vaccines are for religious reasons. Christian Scientists have successfully been convicted of neglect in other incidents where their children died from inadequate medical care, though their religion is the only one I’m aware of that vaccination actually, explicitly violates. 

The constitutionality of religious exemptions is dubious as well. At the very least, however, anyone seeking any exemption should certainly to see a doctor first to be sure they have accurate information and not simply what they have seen online or heard at the playground. Those who absolutely will not vaccinate in states without exemptions may also opt to home school or send their children to private schools that don’t have requirements. But considering the increasing rates of measles and the increasing epidemics of pertussis, the need for high vaccination coverage in communities is more important than ever.

It is true that the pertussis vaccine is not as effective as the old one used to be, something I wrote about a few weeks ago.  It’s also true that pertussis peaks every five years or so, but even taking into account the peaks, the overall rate of cases has been steadily on the move upward. Dr. Offit, the chief of the Division of Infectious Disease at Children’s Hospital of Philadelphia and a very vocal advocate of vaccines, said he believes that parents’ refusals to vaccinate are playing their own small part in the increase.

“The major contributor is waning immunity. The minor contributor is the choice not vaccinate,” he said. He noted that there are researchers working on the problem, as this Nature article notes (paywall), including attempts to make a better vaccine with more adjuvants, the additives that enhance the body’s immune response to a vaccine. While vaccinated children and adults have been high among the numbers of those getting whooping cough, getting the vaccine remains among the best ways to reduce your risk of contracting it — or of having less rough of a time with it if you do get it. Dr. Offit also pointed out that pregnant women in particular should be sure they get their booster.

Which brings us to the study published last week that relates to the most important reason to get vaccinated, at least from the perspective of preventing deaths — to protect the babies who are too young for the vaccine but most likely to contract it and die from it.

The study, published in the journal Epidemiology last week, looked at how frequently pertussis was transmitted to others within the same household and how effective “cocooning” is. Cocooning is vaccinating all the household members who can get the vaccine for the purpose of protecting young babies who can’t yet be vaccinated for the disease.

They found that transmission rates within the home are high, especially for mothers passing the illness on to their children. Therefore, making sure all pregnant women are vaccinated before their baby arrives would, according to their calculations, cut the risk in half that a baby would contract pertussis. The evidence for sibling vaccination, though weaker, still points to the value of overall cocooning: “Vaccination of siblings is less effective in preventing transmission within the household, but may be as effective overall because siblings more often introduce an infection in the household.”

Indeed, this year, siblings’ bringing home the disease appears more likely than ever in the states experiencing big outbreaks this year. Just how bad are the numbers? Well, 2010 was the last five-year peak, which totaled 27,550 cases. It’s currently September of 2012, and the numbers last reported to the CDC were at 29,834, and that doesn’t even include over 3,700 cases in Minnesota that haven’t been officially reported to the CDC yet. These numbers, which include 14 deaths (primarily of babies under 3 months), may very well end up doubling the 2011 total of 18,719 if they continue at the current rate through the end of the year. It’s the biggest pertussis outbreak since 1959.

Not surprisingly, the majority of the states leading in pertussis cases are also among those that offer personal belief exemptions. Washington, despite their new law, is sitting at 4,190 cases, quadrupling their 2011 count of 965. This is the state where 7.6 percent of parents opted for exemptions (among all grade levels, not just kindergarten) in 2008-09, more than four times the national rate of about 1.5 percent. Minnesota and Wisconsin have similarly high rates and both have personal belief exemptions. The most recent numbers out of Minnesota are 3,748 — they had just 661 cases last year. Wisconsin is leading the nation with 4,640 cases, up from 1,192 in 2011, at last report in the Sept. 28 Morbidity and Mortality Weekly Report (pdf) at the CDC.

But the increases are being seen across the nation, as this CDC map shows. Texas (1,287 cases to date this year), Pennsylvania (1,428 cases) and Colorado (897 cases, though they averaged 158 over the past four years) are among other states with personal belief exemptions (though the Texas one has significant restrictions and hoops to jump through). But it’s clear the decreased effectiveness of the vaccine is playing the biggest role, especially in places like Iowa (1,168 cases) and New York (2,107), neither of which offer personal belief exemptions.

Again, though, a less effective vaccine does not mean a worthless vaccine. It still offers 85 percent protection when you get the shot or the booster, and even as it loses some effectiveness as the years go by, you’re far less likely to have a severe case if you do get the disease. And you’re protecting those around you, including the babies who have only been here a few months and are the most susceptible to catching and dying from the disease.

Bottom line — it’s worth it to get the shot, and to make sure your kids do too.

Opinions expressed in this article do not either necessarily reflect or conflict with those of the DXS editorial team or contributors.
[Tara Haelle (www.tarahaelle.com) is a health and science writer and a photojournalist based in Peoria, IL after years as a Texan, where she earned her undergraduate degrees and MA in journalism at UT-Austin. She’s the mental health editor for dailyRx.com in addition to reporting on pediatrics, vaccines, sleep, parenting, prenatal care and obesity. Her blog, Red Wine & Apple Sauce, focuses on health and science news for moms, and you can follow her on Twitter at @health_reporter and @tarasue. She’s also swum with 9 different species of sharks, climbed Kilimanjaro and backpacked in over 40 countries, but that was in the years of B.C. (Before Children). She finds that two-year-olds are tougher to tussle with than tiger sharks.]

Why a UN ban on thimerosal in vaccines would be a big mistake

By Tara Haelle, Health Editor

[This post appeared previously at Red Wine and Apple Sauce.]

Several articles published in Pediatrics today discuss an issue that could affect the protection of children everywhere from vaccine-preventable diseases. The posts center on a controversy that keeps coming up related to vaccines – the  use of thimerosal in them.

All three Pediatrics articles deal with the same thing: an international treaty drafted by the  United Nation Environmental Program’s  Global Mercury Partnership to reduce mercury pollution and environmental mercury exposure across the world. Great! This is an important and valuable initiative – except for one part. As part of the treaty, the UN wants to ban the use of thimerosal, a mercury-containing preservative, used in vaccines. Not so good. The short version for why? This proposed ban threatens millions of children’s lives across the world, including children in the U.S. and in other developed countries. I’ll get to the long version in a moment.

First, the  World Health Organization and American Academy of Pediatricians (AAP) have already pushed for the thimerosal ban provision to be removed from the UN treaty. But today’s three AAP articles drive the point home. One of these provides some  historical context for why thimerosal was removed from childhood vaccines in the U.S. (as  recommended by the AAP and the U.S. Public Health Services in 1999) and in other high-income countries. The other two emphasize just how important it is – and how ethically essential it is –that the ban not be included in the UN treaty.

Here’s the back story:
A  1997 US FDA review of the mercury content in products revealed that the amount of thimerosal in childhood vaccines could, possibly theoretically, build up to exceed the EPA’s guidelines (but not the FDA’s guidelines or those of the Agency for Toxic Substances Disease Registry) on safe exposure limits for  inorganic mercury, called  methylmercury.

Methylmercury is the neurotoxin you hear about when you’re warned not to eat too much fish ( especially while pregnant). Back in 1999, scientists knew a lot about methylmercury, but they didn’t know much about  ethylmercury, the type in thimerosal. As Dr. Louis Cooper and Dr. Samuel Katz, both involved with the 1999 recommendations,  put it, “the absence of clear data for ethylmercury did not allow any assumption to be made about its safety.”

Meanwhile, debates were raging in Congress about concerns over vaccines and autism, fueled by the now-retracted and  thoroughly debunked (pdf) study by Andrew Wakefield  linking the MMR vaccine to autism. Parents were scared and confused. Media coverage was exacerbating the impression that public health officials weren’t being forthright about vaccine risks.

So, poof! All thimerosal was pulled from childhood vaccines except the multi-dose flu vaccine, since kids getting that would only get amounts below the EPA guidelines for methylmercury (even though, again, thimerosal is ETHYLmercury).

Now fast forward to today. We know a LOT more about ethylmercury: namely, that it’s not as bad as methylmercury and  sails through our bodies a lot more quickly. In fact, methylmercury’s half-life is about  seven times that of ethylmercury, which does not build up in the body like methylmercury does.
“There is no credible scientific evidence that the use of thimerosal in vaccines presents any risk to human health,” writes Dr. Katherine King in one of  today’s Pediatrics articles. Dozens of studies and a massive review at the Institute of Medicine back this up.

Thimerosal in vaccines is not a problem. But what is a problem is thimerosal’s PR image. Again, from one of  today’s AAP articles: “Given the complexity of the science involved in making guidelines, the polarity between vaccine advocates and those believing their children have been harmed, the media’s attraction to controversy, and, in retrospect, inadequate follow-up education about the issues to clinicians and the general public, it is not surprising that the steps taken left misunderstanding and anxiety in the United States and concerns in the global public health community.”

Basically, they’re saying, yea, we kinda screwed up with conveying that thimerosal really IS safe after all. We wanted to be over-cautious before, and we were, and that was good, but now we’ve sorta dropped the ball on following through in letting you know that YOU HAVE NOTHING TO WORRY ABOUT with the ethylmercury in thimerosal. As Dr. Walter Orenstein  today’s AAP articles, “Had the evidence that is available now been available in 1999, the policy reducing thimerosal use would likely have not been implemented. Furthermore, in 2008 the World Health Organization endorsed the use of thimerosal in vaccines.”

But apparently, the WHO’s endorsement can’t overcome thimerosal’s PR image problem in the eyes of the UN. And so the UN is short-sightedly and dangerously trying to ban thimerosal in vaccines.

Well, that just means getting rid of it in flu vaccines (many of which don’t even have thimerosal since they’re single-dose), so what’s the big deal anyway? The big deal is that not all countries got rid of thimerosal in their childhood vaccines. Many high-income countries like the U.S. did – because they could afford to be overly cautious.

But more than 120 middle- and low-income countries – including the developing countries where vaccine-preventable diseases have the highest rates of infection and death –  have continued using thimerosal-containing vaccines because the preservative allows them to make cheaper vaccines that withstand less rigorous storage without compromising safety.

Getting rid of thimerosal would mean overhauling vaccine production and storage in those countries, which the WHO estimates would cost more than  $300 million for vaccines supplied by UNICEF or the Pan American Health Organization alone. As Dr. King argues, “it is banning thimerosal that would cause an injustice to those living in low- and middle-income countries and relying on these vaccines for effective protection against many harmful infectious diseases.”

Why does this matter to people in the U.S. or in other higher income countries? Because we live in a global world. Vaccines with thimerosal are currently used to immunize about  84 million children across the world every year, saving an estimated 1.4 million lives from vaccine-preventable diseases.That also includes lives saved in developed countries, where a future outbreak could potentially be imported from other countries in which a vaccination program may have ceased following a thimerosal ban.

More simply put: If the UN forces the removal of thimerosal from vaccines, then 84 million children risk not getting vaccinated (and/or vaccinated on time) due to delays in vaccine production or due to a shortage of vaccines because of increasing costs. This, in turn, could (and likely would) mean an increase in vaccine-preventable infections, which will, in turn, kill more children worldwide and risk disease carriage to other countries.

Over and beyond the increases in vaccine-preventable infections and deaths throughout the world, a thimerosal ban in vaccines could also still pose problems for developed countries. In an emergency, as Dr. Orenstein and colleagues argue, not being able to manufacture vaccines with thimerosal could endanger lives during an epidemic if it slows down vaccine production. This proposed UN ban – and the necessity of its removal – matters.

Dr. Cooper and Dr. Katz – again, both pediatricians who were closely involved in the original 1999 decision to pull thimerosal out of vaccines – sum it up best: “The World Health Organization recommendation to delete the ban on thimerosal must be heeded or it will cause tremendous damage to current programs to protect all children from death and disability caused by vaccine-preventable diseases.”

Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

The short version
  • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
  • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
  • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
  • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
The longer version
Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.


Big Molecules with Small Building Blocks

The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.

You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

Sugar and Fuel

A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

Polysaccharides: Fuel and Form

Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

Lipids: The Fatty Trifecta

Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

Fats: the Good, the Bad, the Neutral

Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

Phospholipids: An Abundant Fat

You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

Steroids: Here to Pump You Up?

Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.


As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

Levels of Structure

Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

A Plethora of Purposes

What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

Nucleic Acids

How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

DNA vs. RNA: A Matter of Structure

DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

DNA vs. RNA: Function Wars

An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.

 By Emily Willingham, DXS managing editor 
This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

Striking a balance between health and sustainability: a study inspired by a love for sushi

Sushi for sale (Source)
by Jeanne Garbarino, DXS biology editor

A conservation scientist walks into a [sushi] bar…

You’ve probably heard that eating a diet including fish, especially fatty fish, is good for us. Fish can be a source of high quality, lean protein, and also provide heart-healthy omega-3 fatty acids. However, there are risks associated with eating some types of fish. For instance, fish that are at the top of the food chain or have a long lifespan (or both!) can accumulate high levels of mercury or chemicals called polychlorinated biphenyls (PCBs).  Exposure to high amounts of these compounds could be particularly harmful for pregnant/nursing women or young children.

On the other hand, there is the issue of sustainability. We are seeing a wide-scale collapse of many marine fish populations, which is primarily the result of overfishing.   While there are conservation efforts in place to help consumers make eco-friendly choices, it is not clear if raising consumer awareness is impacting fishing or marine farming practices. Furthermore, many consumers will choose fish based on their nutritional value and safety without really considering ecological consequences.

In an attempt to better educate consumers on both nutrition andsustainability with regard to making the best seafood choices, Leah Gerber, professor of Ecology, Evolution and Environmental Science at Arizona State University, has evaluated current fish “eco-ranking” schemes. In a study recently published (PDF) in Frontiers in Ecology and the Environment, Dr. Gerber provides a model that quantifies both the health benefits and sustainability level of individual fish species.

Interestingly, her group found that fish with the highest health benefits, determined by omega-3 fatty acid content, generally had low mercury levels. Similarly, fish that are unsustainable — meaning that fishing threatens their existence — tended to have higher levels of mercury, and lower omega-3 fatty acid amounts.  Basically, fish populations that are not threatened by overfishing are generally heart healthy and have low mercury. A win-win!

The novel thing about this study is that it is the first to consider multiple types of sustainability rankings as well as health impacts, and Dr. Gerber is taking her message to the streets. It is her hope that she and her colleagues will be able to develop tools so that consumers can easily make seafood choices that are both good for you and good for the environment.

But the coolest thing about this study is that Dr. Gerber is not a ‘fisheries person’, per se.  However, her passion for learning about human impact on the natural environment combined with her love of sushi prompted a closer look at the fishing industries and how to make good choices when it comes to seafood.

This is an excellent example of how a scientist is applying her knowledge to promote science in one of its most relatable forms –- eating!  I mean, we all have to eat, and it is particularly awesome when we can do so in the most educated way possible. Kudos to Dr. Gerber for taking this on since we all benefit from knowing.  

The opinions expressed in this article neither necessarily reflect nor conflict with those of the DXS editorial team.

To Cut or Not to Cut…Cirumcision Decision

“You wanna do WHAT?!” Photo courtesy of Justyna Furmanczyk at sxc.hu.
By Tara Haelle, DXS contributor
[Tara Haelle (www.tarahaelle.com) is a health and science writer and a photojournalist based in Peoria, IL after years as a Texan, where she earned her undergraduate degrees and MA in journalism at UT-Austin. She’s the mental health editor for dailyRx.com in addition to reporting on pediatrics, vaccines, sleep, parenting, prenatal care and obesity. This post first appeared on her blog, Red Wine & Apple Sauce focuses on health and science news for moms (www.redwineandapplesauce.com), and you can follow her on Twitter at @health_reporter and @tarasue. She’s also swum with 9 different species of sharks, climbed Kilimanjaro and backpacked in over 40 countries, but that was in the years of B.C. (Before Children). She finds that two-year-olds are tougher to tussle with than tiger sharks.]
So you’ve likely heard by now that the American Academy of Pediatrics issued their updated policy statement on circumcision, the first since 1999. I’ve been sitting on the statement and the task force technical report for a week now, and even though I’ve written a news summary for dailyRx…  I have many mixed feelings.
I am grateful that their statement was issued with the sensitivity and caution needed for such a controversial practice and decision. Some of the headlines have been frustrating, implying that the AAP said “Circumcision is better.” Um, no. That’s not what they said. They said that the “preventive health benefits of elective circumcision of male newborns outweigh the risks of the procedure.” (To be fair, most headlines basically ran with “benefits trump risks” or some variation thereof.)
In other words, if you choose to do this procedure, the benefits you will gain are greater than the risks involved in the procedure. This is very different from saying “It’s better to be circumcised.” In fact, their policy explicitly points out that they do not officially “recommend” the procedure routinely: “Although health benefits are not great enough to recommend routine circumcision for all male newborns, the benefits of circumcision are sufficient to justify access to this procedure for families choosing it and to warrant third-party payment for circumcision of male newborns.” (That last part just means yes, insurance companies, you should pay for it.)
An analogy: A child with obstructive sleep apnea can have a tonsillectomy/adenoidectomy (called an adenotonsillectomy) to remove their tonsils and adenoids for treatment. The tonsils and adenoids (lumps of issue behind the nose) generally cause the blockage that interferes with a child’s breathing while asleep, so removing them can usually cure the sleep apnea (in 75 to 100 percent of the cases).
There are risks to adenotonsillectomy, namely infection and excessive bleeding. There are risks to sleep apnea, including obesity, heart disease, diabetes, depression and death. For a child with obstructive sleep apnea, the benefits generally outweigh the risks of the procedure. A parent can still elect not to give their child the surgery.
Is it better for the child with sleep apnea to have the surgery? Probably. But perhaps not. It depends on the situation and the child. Is it better for a child without obstructive sleep apnea to have the surgery? Of course not. Why take any risk when there’s no benefit?
Now consider the two primary benefits conferred by circumcision: lower risk of urinary tract infections during the first year and reduced risk of HIV and a several other sexually transmitted infections during heterosexual sex. The risks of circumcision are most commonly bleeding, infection or the wrong amount of tissue snipped off, and this happens in about 1 of every 500 newborn boys (0.2 percent). Other studies found the rates higher, up to 2 to 3 percent, but these complications were still just minor bleeding. They even offered a comparison of a similar surgery as the one I discussed above: complications involving severe bleeding from tonsillectomies occur about 1.9 percent of the time in kids age 4 and under.
For parents with wild imaginations about horror stories, fear not: “The majority of severe or even catastrophic injuries are so infrequent as to be reported as case reports (and were therefore excluded from this literature review). These rare complications include glans or penile amputation, transmission of herpes simplex after mouth-to-penis contact by a mohel (Jewish ritual circumcisers) after circumcision, methicillin-resistant Staphylococcus aureus infection, urethral cutaneous fistula, glans ischemia and death.” Basically, yea, there’s a bunch of really bad stuff that can happen, but it’s really, really, really, really rare. Probably rarer than being struck by lightning. Twice. But that happens too.
So, the risks are pretty low. How beneficial are the benefits? Here’s a condensed run-down from the AAP’s technical report:
  • Circumcision reduces the odds of contracting HIV during male-female sex by 40 to 60 percent… in Africa. When the CDC calculated that figure with the rate of contracting HIV by heterosexual sex in the U.S., they came up with a 15.7 percent reduction here. It’s something, but nowhere near as good as a condom. Plus, if your kids turns out to be gay, there’s not much evidence that circumcision helps him avoid contracting HIV. (And on the other side of the coin, circumcision can make it a little easier for women to contract HIV from a man, per one study cited in the AAP review.)
  • Circumcised men are about 30 to 40 percent less likely to get any type of human papillomavirus (HPV), including both the relatively harmless strains and the ones that can lead to cervical cancer or raise your risk of cancer of the mouth, throat, penis and anus. Now, the CDC has recommended that boys get the HPV vaccine, but the vaccines available do not cover all the strains. Gardasil takes care of four of them, including the two responsible for about 70 percent of cervical cancer (HPV-16 and HPV-18) and the two responsible for 90 percent of genital warts. Cervarix only takes care of HPV-16 and HPV-18. So, circumcision would offer some protection against getting the HPV strains that the vaccines don’t cover, most of which — but not all — are not linked to cancer or warts.
  • There’s some evidence that circumcision reduces risk of herpes (HSV-2) by about 28 to 34 percent, based on two studies in Africa.
  • Evidence for protection against syphilis is weak. There’s no evidence that circumcision decreases the risk of contracting gonorrhea or chlamydia.
  • There’s good evidence that uncircumcised boys get more urinary tract infections that circumcised boys, in part because bacteria can hang out in that moist area under the hood. The AAP estimates that 7 to 14 of every 1,000 uncircumcised boys will get a UTI before their first birthday, compared to 1 to 2 out of 1,000 circumcised boys. With such a low rate overall, in either population, the AAP notes that “the benefits of male circumcision are, therefore, likely to be greater in boys at higher risk of UTI, such as male infants with underlying anatomic defects such as reflux or recurrent UTIs.” (These are mostly the boys that get UTIs anyway.)
So, those are definitely some benefits to circumcision, especially if your little guy will have sex one day (which, presumably, you want him to do at some point in the far off, I-don’t-want-to-think-about-it future). It’s also fair to say that good sex education and condom use would make those benefits almost moot (not the UTIs, which are pretty low risk, and not all HPV strains, which sometimes infect even with condom use).
In any case, these two benefits, a lower risk for UTIs and some STIs, then become the risks of not being circumcised. The former is — usually — not very serious. There are some very serious urinary tract infections, and untreated ones can damage the kidneys. And they’re certainly not fun. They aren’t, however, usually life or death situations. HIV (somewhat still) is. Of course, boys are still at a pretty high risk for getting HIV if they sleep with someone who has it and don’t use a condom, circumcised or not. But every bit of protection helps, right?
Unless it requires lopping off part of a little boy’s penis. There. I said it. Because that’s what many parents are simply uneasy about, regardless of the health benefits, which are great or marginal, depending on your perspective. And that’s why the AAP stopped short of recommending circumcision as a routine procedure.
They did include in their review several studies related to sexual satisfaction and sensitivity, one of the complaints that “intactivists” bring up. The AAP summarizes it pretty nicely: “The literature review does not support the belief that male circumcision adversely affects penile sexual function or sensitivity, or sexual satisfaction, regardless of how these factors are defined.”
But it’s not possible to take into consideration, in scientific, mathematical terms, the primary complaint of those who oppose circumcision, which is that the man these little boys become may have wanted that little flap over the tip. And this is one of those gray areas that give parents pause. Once you cut that hood, you can’t put it back. How many circumcised men regret what their parents did? Well, probably not vast numbers, or circumcision rates would have plummeted.
Rates have, in fact, decreased, from somewhere around three-quarters of all boys in the 1960s to around 55 to 59 percent in 2010. (Here’s a nifty map to see where your states’ rates are.) But they haven’t plummeted.
So, this is where we end up. There are some decent benefits. There are very few and mostly minor risks to the procedure. And there’s big, giant, gray unknown area of “what if’s” and “could have been’s” for the boys who get snipped. It’s disingenuous to compare the practice to female circumcision, as some do, since neither its intent nor its effect is to influence sexual satisfaction. But whether it’s the right thing to do…? The AAP says it’s up to mom and dad. (Which, in many households, like mine, probably means mostly dad.)
“Parents ultimately should decide whether circumcision is in the best interests of their male child,” they wrote. “They will need to weigh medical information in the context of their own religious, ethical, and cultural beliefs and practices. The medical benefits alone may not outweigh these other considerations for individual families.”
What are those other considerations? Well, whether you want your little guy to have a foreskin. Or, whether you don’t know if he does or doesn’t want it and figure he should decide that in 18 years. Maybe daddy’s not circumcised and you both want him to look like daddy. (I know many people who circumcised for this reason alone.)
About the only certain thing that can be said about circumcision, based on the AAP’s policy statement and research and what we know about opposition to the practice, is that this controversy will be with us for years to come.
The opinions in this post do not necessarily reflect or disagree with the opinion of the DXS editorial team.

On Parenting, Science, and Trust

The following was originally posted over at The Mother Geek (RIP) in January of this year.  The guest author is Alice Callahan, who is a research scientist turned stay-at-home mom. She lives in Eugene, Oregon, with her husband and 14-month-old daughter. Alice writes about the science of parenting, as well as her adventures in mothering, at scienceofmom.com.  You can also find Alice on Twitter.
Via Creative Commons

Having a PhD in science makes my job as a mother easier – but maybe not in the ways that you might expect.

My PhD is in Nutrition, so you would think that getting my kid to eat well would come easy for me. Unfortunately, that has not been the case.  I’ve logged more than two years of postdoc research on fetal programming – how the uterine environment affects outcomes in babies. You might think that this helped me to do everything right during my pregnancy. Instead, I think it just led to more worry about all of the ways I might be damaging my unborn child. Stress! Sugar! BPA! Lab chemical exposure! OMG! More stress!
Sure, I have more knowledge than the average mother. Sometimes that is helpful.  And sometimes it is not. And knowing how to do a literature search to try to answer my parenting questions often leads to further sleep deprivation as I slog through Pubmed hits and come out on the other side with more confusion. Sometimes my drive to find scientific answers for my parenting questions just distracts me from my instinct – not that my maternal instinct is all that amazing, but I do know my baby better than anyone else in the world.
So how does being a scientist make parenting easier for me? As a scientist mother, I trust other scientists. And I trust doctors. I even trust government agencies, which bring together the best scientists and doctors in a field to review the research and make recommendations for the good of public health.
I trust scientists and doctors, because I have worked side-by-side with them for a decade, andI know that they are not only knowledgeable,but by and large, they are overwhelmingly good people. At some point, you have to trust someone.

I trust scientists and doctors.   

I trust scientists, because I know that the vast majority of them are just underpaid nerds who are really passionate about what they do. They are driven by the desire to find the truth about a question and they work, day in and day out, in that pursuit.  In addition, I know that scientists don’t always agree, so when there is a general consensus among the majority of scientists about something, such as vaccine safety or global warming, I feel confident in that conclusion.
Contrary to many claims on the Internet, scientists are not in bed with Big Pharma, conspiring make millions at the expense of your child’s health. They are in bed with their husbands and wives, probably chatting about their latest failed cell culture experiment.
I also trust science because I understand the peer review process all too well. Although it has its flaws and as maddening as it is when I am the one being reviewed, I have confidence that the peer review process is highly effective at weeding out the kooks and pseudoscientists and the conflicts of interest. (Unfortunately, there are a few kooky psuedoscientists out there with serious conflicts of interest, and it just so happens that one of them managed to publish fraudulent research linking the MMR vaccine and autism. Many studies have since shown that such a link does not exist, but it took 12 years for Andrew Wakefield’s Lancet paper to be retracted. How many dollars have been spent and how many people made sick or worse in the continuing fallout and confusion about this public health scare? When the peer review system fails, it can be truly devastating.)
I trust doctors because I know that most of them are, first and foremost, humanitarians at heart, especially those that have chosen to work in primary care. I know how hard doctors work to become competent in the vast ocean of information about pathologies of the human body. I know how seriously they take their responsibility of our health.
I especially trust pediatricians. They have chosen one of the lowest-paid specialties simply because they love working with kids. I know that every pediatrician, at some point during her training or career, has likely cared for a child who was dying of a disease that could have been prevented by vaccination, and that memory haunts her as she faces parents afraid of vaccinating their children. Doctors are not conspiring against us. They want to help us make the best choices for our children, more than anything in the world.
Because I trust scientists and doctors, I didn’t question the CDC’s vaccination schedule. I didn’t pore over vaccine research or agonize about the decision to vaccinate my child. Instead, I trusted that the committees of experts at the CDC and AAP carefully make the best recommendations possible based on the data available.
Maybe that is naïve. Maybe I am a lazy mother for not trying to become a vaccine expert before I allowed those first needles to enter my daughter’s thigh. Maybe. But I also think it would be naïve for me to think that I could become an expert on vaccinations, that I could know and understand the field better than the committees of scientists and doctors who have made this their life’s work.
I know how much work it took me to become an expert on one or two corners of nutrition and fetal physiology. It took thousands of hours of reading textbooks and journal articles, sitting in lectures, attending conferences, and struggling at the lab bench before I started to feel even a little bit comfortable calling myself an expert in any field. So I think it is naïve for a parent to think that she can become an expert on vaccines by spending some time on the Internet, reading questionable sources, almost all of which have some agenda. I accept that I can’t know everything, and I have enough faith in humanity that I trust others who know more than me.

It is not that I don’t question scientists and doctors. I do. For example, I recognize that government agencies and medical organizations often have a lag time for adopting the latest science into their recommendations. I recognize that tradition, culture, politics, and economics all influence those recommendations, and they are not without fault.
I certainly question my doctors, because I know they are each fallible human beings, and they can’t know everything. I brought a stack of journal articles to my OB to convince her to delay cord clamping at my delivery. I did so much research on infant iron nutrition and came to my daughter’s 9-month checkup with so many questions that my pediatrician looked me in the eye and said, “You’re worried enough for both of us about BabyC’s iron.” Although I question my doctors, I also trust that they are adept at discerning fake science from real science. If I bring my doctor the sources I am using to inform my questions or concerns, she should be able to judge whether or not they are trustworthy and have a real discussion with me about factors that I may not have considered.
In truth, I do follow the vaccine debate closely, but not because I wonder if I am doing the right thing by vaccinating my child. I follow the vaccine debate out of interest for how misinformation can explode in a way that creates a public health crisis. I find myself increasingly concerned about the low rate of vaccination in my own community. I worry for the newborns in our town who have not yet had a chance to be vaccinated and for the individuals who cannot be vaccinated due to health conditions. I am starting to feel like I have a responsibility to share accurate information with mothers and fathers struggling with the decision of whether or not to vaccinate, because misinformation is doing real harm.

It is good to question our parenting decisions and in doing so, become more educated about them. However, as a scientist, I’m happy to defer to other scientists about some of the biggest parenting decisions I have faced. I am grateful for their decades of research forming the foundation of our understanding of child health and for the good-hearted doctors who care for my family. They have made my job as a mother a lot easier. I can spend less time worrying and more time playing with my daughter and soaking up the time with her as she grows up way too fast.

Thanks, science, for making it easier to be a mom.

These views are the opinion of the author and do not necessarily reflect or disagree with those of the DXS editorial team.