Sunday, December 30, 2012

The toxic list: problems that pregnant vegans DON'T have

Mainstream pregnancy books rarely mention veganism at all, and when they do, it's usually to warn that vegans are at a greater risk of nutritional deficiencies compared to omnivores.  This is not completely unreasonable, but it misses important benefits of a plant-based diet: vegans have a lower risk of many pregnancy problems, ranging from gestational diabetes in the mother to spina bifida in the baby.

This is obvious if you look at a typical list of "foods to avoid in pregnancy": fish high in mercury; soft cheese; hot dogs; sushi; undercooked eggs; medium-rare hamburgers... and it goes on.  None of these foods form part of a vegan diet.  All of them carry serious health risks in pregnancy.

Sources include March of Dimes, Drugline, and Otis Pregnancy
In theory, it should be easy for omnivores to cut these out of their daily diets.  In practice, old habits die hard.  A significant percentage of women continue to drink alcohol throughout their pregnancies, in spite of the well-known risks.  Why would it be any easier for pregnant women to cut out hot dogs, sushi, or smoked salmon?

On top of this, a significant percentage of pregnancies are unplanned -- in the U.S., it's around 40%.  (Bombshell, I know!)  This increases the likelihood that a pregnant woman will consume risky foods before she realizes that there's a small human growing inside her uterus -- and it increases the benefits of veganism before and during those early stages of gestation.

"But my friends said you couldn't get pregnant on prom night!"

If you gave up animal products as an adult, you probably got to experience the clear-up effect, in which you stopped having mysterious episodes of 24-hour "stomach flu" and other miscellaneous gastrointestinal disasters.  As Eric Schlosser explained years ago in Fast Food Nation, there's no such thing as a 24-hour flu: those fun experiments with diarrhea and projectile vomiting are actually cases of food poisoning, and are almost always caused by the consumption of animal products.

The clear-up effect is even more valuable to pregnant women, because pregnancy suppresses the immune system to prevent it from rejecting the fetus as a parasite.  The body tries to compensate for this immune suppression by building more leukocytes (white blood cells that fight infection), but you may still be more vulnerable to common meat-borne pathogens.  These infections can cause irreversible developmental damage to the baby.

On the "foods to avoid" list, there are, of course, problems other than bacteria: e.g. parasites, mercury, and other industrial pollutants.  Eating fish contaminated with mercury can cause neurological damage to the infant, leading to problems such as retardation, seizures, and at lower levels, ADHD.

A recent scientific study found that the greater a woman's exposure to mercury during pregnancy, the more likely her child was to exhibit ADHD-type behaviors, and even low levels of mercury exposure were risky.  This exposure comes directly from eating fish.  The authors concluded, however, that consuming fish low in mercury had a protective effect against these same developmental problems.

My conclusion is simpler: don't eat fish at all.  There is no known safe level of mercury exposure in pregnancy.  Get your fatty acids elsewhere -- like chia seeds, seaweed, or vegan supplements if necessary.  It's better for the mother, the baby, and the fish.

Toxoplasma gondii: beautiful & deadly
One final point: pregnancy books will tell you not to touch kitty litter because of the risk of acquiring toxoplasmosis, a parasite that can affect humans as well as cats.  Toxoplasmosis has a range of bizarre effects on adults; it's implicated in cases of schizophrenia and risk-taking behavior, among other things.

Exposure in utero has a much more nasty range of outcomes.  However, pregnancy books rarely explain that the consumption of undercooked meat is another major way of getting toxo into your system.  (Unwashed vegetables can also be contaminated, because toxo also lives in dirt -- wash your damn vegetables!  The difference is that you cannot wash toxo out of meat.)

Jaroslav Flegr, a toxoplasmosis specialist, points out that:
Humans ... are exposed not only by coming into contact with litter boxes, but also, he found, by drinking water contaminated with cat feces, eating unwashed vegetables, or, especially in Europe, by consuming raw or undercooked meat. Hence the French, according to Flegr, with their love of steak prepared saignant—literally, “bleeding”—can have infection rates as high as 55 percent.  [Source: The Atlantic]
By comparison, Americans have an infection rate of only 10-20%, in spite of high rates of cat ownership in both countries.

It is frustrating that the doctors who write mainstream baby books think of veganism solely in terms of its risks and not in terms of its rewards.  My reasons to be vegan are ethical first; however, there are numerous secondary benefits -- to health, to the environment -- and pregnant vegans have lots of reasons to be cheerful.

Monday, December 24, 2012

Science of Vegan Pregnancy 01: maternal serum screening and blood levels of vitamin B12

Nearly ten years ago, a group of Taiwanese researchers came out with a study showing that vegan and vegetarian pregnant women were more likely to receive false positives on a common test called a "maternal serum screening."  This is a big deal for veg*an pregnancies because a positive MSS result can lead to a more invasive procedure, an amniocentesis, that carries a chance of miscarriage and other damage to the fetus.  And of course, a false positive can lead to a lot of unnecessary distress.

In effect, "normal" test results for veg*ans don't look the same as normal test results for omnivores, and that information should affect how doctors interpret our tests.

Maternal serum screening tests for the likelihood that a fetus has Down's syndrome.  The test is a numbers game: it doesn't give you a yes or no answer.  It only determines whether you (the pregnant woman) are more or less likely than other women your age to have a Down's syndrome baby.

MSS measures the levels of several different proteins in a pregnant woman's blood: typically human chorionic gonadotropin (hCG), alpha-fetoprotein (AFP), and unconjugated estriol (uE3), sometimes with the addition of inhibin A.  (FYI, hCG is the same hormone that is detected by pregnancy tests.

If the hormone levels are off (some higher than average, some lower than average), the test will come back positive.  An elevated level of hCG is a risk factor.

Open for interpretation?
[image credit here]
I started looking into this because I'm vegan, and my MSS results came back positive.  That is, I had an elevated chance (compared to other women my age) of having a baby with Down's syndrome.  The previous month, my overworked and barely-English-speaking GP recorded an incorrect date of conception, which meant that I did not receive another common Down's syndrome screening test (a nuchal translucency ultrasound).  Thus, the MSS was the only test we had to go on when deciding whether or not to get an amniocentesis -- and where to go from there.

Enter google scholar, which directed me to this article on MSS and vegetarianism.  The authors of the study are Taiwanese doctors working with Taiwanese women.  Taiwan is a particularly good place to conduct research on vegetarianism and health because: 1. it has a ton of research hospitals; 2. a high proportion of the population is vegetarian for religious reasons -- mostly Mahayana Buddhism, but also various forms of neo-hybrid-Buddhist-Daoism, and completely original religions like that of Supreme Master Ching Hai, who tells all her followers to be vegan.  Taiwan even has a dedicated Buddhist research hospital where all the canteens serve vegetarian food.

We don't all have our own TV stations... [image credit here]
Back to our study.  Cheng et al, the authors of the study, found that:

Vegan and vegetarian pregnant woman have higher average levels of b-hCG.

• This means that midtrimester serum screening produces more false positives for vegan and vegetarian pregnancies.

There's a correlation between lower vitamin B12 levels and higher b-hCG levels.  Thus, women with a lower concentration of vitamin B12 in their blood (but who are not necessarily deficient in vitamin B12) are more likely to get a false positive test result.

• The greater number of false positives on the test leads to more invasive and unnecessary screening procedures (such as amniocentesis) for vegan and vegetarian pregnant women.

And finally...

Low vitamin B12 levels do correlate to at least one other "danger signal" in pregnancy, namely, higher levels of plasma homocystine (associated with a host of nasty problems -- birth defects, pre-eclampsia, etc. etc.).  So in theory, it's possible that low vitamin B12 levels in vegan and vegetarian women would correlate to these kinds of pregnancy complications -- but, as the authors point out, this question needs further research.  (I ain't panicking -- but I am taking B12 supplements, and have been throughout the pregnancy.)

So what happened with my test results?

My GP sent me to an OB/GYN, who told me not to panic.  He arranged a further ultrasound screening that indicated a lower than average likehood of Down's syndrome.  I opted for no amniocentesis.  And that's the end of that story (until the baby's born).

I did tell my OB/GYN about the study, but I live in a town with approximately 2 other vegans, one of which I'm married to... so he may never meet another pregnant vegan in his entire career.

And fortunately, neither my GP (who is a caste vegetarian) nor my OB/GYN (an average beef-eater) ever tried to argue me out of veganism.


Cheng PJ, Chu DC, Chueh HY, See LC, Chang HC, Weng DR.  2004.  "Elevated maternal midtrimester serum free beta-human chorionic gonadotropin levels in vegetarian pregnancies that cause increased false-positive Down syndrome screening results."  American Journal of Obstetrics and Gynecology, Vol. 190 (No. 2), pp. 442-7.