Saturday, December 08, 2007

Vegetarian Diet in Pregnancy: Insulin Resistance in Children

For many years now there has been a push in the United States to convince the public they need to consume less animal foods and more plant-based foods. Earlier this year I reviewed our dietary habits based on consumption patterns in the US as documented by the Food and Agriculture Organization (FAO) and the Economic Research Service (ERS) of the USDA and was really shocked by the level of intake for added sugars, cereal grains and vegetable oils.

The most recent assault on common sense came this week when Newsweek featured The Fertility Diet on its cover, promoting it and the findings from epidemiological data that was the basis of the book as a proven way to eat to enhance fertility. As I noted in my review of the book and study earlier this week, the study findings and book "do not make a proven strategy or evidence-based approach to prevent or reverse ovulatory dysfunction."

I didn't write much about the potential effects on babies born to women consuming such a diet because the post was already very long. However, it needs to be discussed considering new data published this week. For all intents and purposes, The Fertility Diet is recommending a predominently vegetarian diet - limit red meat and animal foods, strictly limit saturated fat, favor protein from beans and include full-fat dairy. This is almost identical to how the population in India eats!

Blogging on Peer-Reviewed ResearchA study published in the January 2008 issue of Diabetologia, Vitamin B12 and folate concentrations during pregnancy and insulin resistance in the offspring: the Pune Maternal Nutrition Study, highlights the profound effect on the offspring of women consuming an habitual vegetarian diet. [link opens to full-text of paper]

In the abstract we learn the researchers set out to understand how elevated total plasma homocysteine concentrations predict birth weight and risk factors for type II diabetes - "We studied the association between maternal vitamin B12, folate and tHcy status during pregnancy, and offspring adiposity and insulin resistance at 6 years."

To do this they followed 700 pregnant women in six villages (and their children) over six years; "We measured maternal nutritional intake and circulating concentrations of folate, vitamin B12, tHcy and methylmalonic acid (MMA) at 18 and 28 weeks of gestation. These were correlated with offspring anthropometry, body composition (dual-energy X-ray absorptiometry scan) and insulin resistance (homeostatic model assessment of insulin resistance [HOMA-R]) at 6 years."

What the researchers found was not only disturbing, but may have long-term implications not considered critical to long-term health of children previously.

In the table presenting the maternal nutrition data during pregnancy, we learn the women consumed adequate calories - the majority did not consume meat, poultry or fish, but did consume dairy (milk, yougurt, cheese, etc.).

At week 18 of pregnancy, the majority of calories in the diet came from carbohydrate - 70%, fat contributed 17% of energy and protein 13%; at 28 weeks of pregnancy the dietary macronutrient ratios were similar - carbohydrate 72%, fat 16%, protein 12%. The women (without folic acid supplementation) consumed a diet righ with foods high in folate, as evidenced by the finding that only one woman in the whole group was deficient for folate - all others exceeded levels desired in pregnancy.

Alarming however was the finding that the majority were deficient for vitamin B-12 - 60% of the women had blood levels of B-12 less than 150pmol/l. While the finding was alarming, it was not unexpected since the women were not consuming meaningful intakes of animal foods from which we find vitamin B-12 in our diet - the majority of the women were vegetarian, consuming a high carbohydrate, low-fat diet - the type of diet, in fact, promoted in The Fertility Diet book.

The women in the study seem to have done well in their pregnancies and gave birth to healthy babies, some were low birth weight, but as I said, they were overall "healthy."

So why then am I writing about this study?

Well, the effect on their children, over the next six years was telling and speaks volumes about how diet and micronutrient intakes during pregnancy may effect offspring.

When the researchers followed up on the children six years later, they found a seemingly healthy bunch of kids - "At 6 years, the children were light, short and had a low BMI compared with an international (UK) reference; none were overweight or obese as defined by International Obesity Task Force criteria."

You would think that was good news, wouldn't you?

Well, it wasn't their outward appearance or their normal BMI that was problematic, it was their fatness and insulin resistance at age six that shocked the researchers!

"...skinfold thickness measurements showed that the children were relatively truncally adipose; the mean SD score for subscapular skinfold thickness was -0.42 compared with the UK growth standards, in contrast with -2.23 for weight and -1.86 for BMI. Higher fat mass and higher body fat per cent were associated with higher fasting insulin concentrations, higher HOMA-R and higher 120 min plasma glucose concentrations (p = less than 0.05 for all)."

A few paragraphs later we learn, "The highest HOMA-R was in children whose mothers had the lowest vitamin B12 and highest folate concentrations."

What this means is that the children born to women consuming the highest levels of folate rich foods - green leafy vegetables and beans - and the least (or none) animal foods, had children with the highest risk of insulin resistance!

The researchers opened their discussion section bluntly, "We have demonstrated for the first time in a purposeful, community-based prospective study an association between maternal nutritional measurements in pregnancy and two major risk factors for type 2 diabetes in the offspring," and didn't stop there, "higher maternal folate concentrations predicted greater adiposity (fat mass and body fat per cent) and higher insulin resistance, and lower vitamin B12 concentrations predicted higher insulin resistance. Children born to mothers with low vitamin B12 concentrations but high folate concentrations were the most insulin resistant."

They concluded with "...our data raise the important possibility that high folate intakes in vitamin B12-deficient mothers could increase the risk of type 2 diabetes in the offspring. This is the first report in humans to suggest that defects in one-carbon metabolism might be at the heart of intra-uterine programming of adult disease."

If you are pregnant or planning to conceive, you may want to think twice before shunning foods that provide vitamin B-12 - meats, eggs, poultry, fish and dairy!

11 comments:

  1. Anonymous10:35 AM

    Nothing like speaking from PROSPECTIVE, HUMAN evidence!

    Epidemiologists: Take Note

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  2. I tend to think women who eat the least b12 in pregnancy were the strictest vegetarians.

    The effects at 6 years may be due to the prenatal nutrition, but I"m more inclined to think crazy-vegetarian mommy won't let baby bird eat anything but granola and dried fruits from trader joes. Women with higher b12 intakes are either more nutritionally responsible, or they aren't as strict in vegetarian practice, and this affects how they feed their children.

    Result of strict vegetarianism: your 6 year old child who is more insulin resistant and fatter (although not heavier) than their peer who eats a more balanced diet including animal foods.

    If the children were not malnourished on vegetarian diets they would probably have little to no differences next to their balanced-diet peers. After all, the diet of the non-vegetarian woman isn't exactly going to give baby the best metabolic head start there is (how many women use pregnancy as an excuse to indulge in carb addiction anyway, with the blessing of their physician? If anything, I would expect an average american non-vegetarian woman to eat just as many carbs as a vegetarian woman, except with a lot more fat and animal products arguably worsening insulin resistance due to the extra burden of dietary fat they cannot metabolize. )

    Vegetarian diets: bad for adults, bad for children.

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  3. I find myself bein in the rather odd position of defending vegetarian diets. In this instance, I think a distinction needs to be made between variations vegetarianism. A lacto-ovo diet, the traditional form of vegetarian diet, can be a healty way of eating for some people. I live in a community where this particular way of eating is popular. There are also a few vegan extremist. It is not hard to tell which children belong to which parents. The folks who are L-O tend to be a robust bunch whose children have "milk and honey" complexions. The vegan kids tend to be a pasty bunch, who are often seen stuffing their faces with junk outside of parental supervison. While this is strictly anectdotal, I don't see any vegan grandparents, but many of the L-O's are grand parents and have been eating a whole food, L-O diet for decades.

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  4. The diet intake during Pregnancy can make a lot of difference to the child health. However sticking to vegetarian diet is good for resistance,nice informative post, looking for more updates thank you

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  5. I'm from Japan.
    Glad to meet you.

    Please link to this site.
    Keep it up please.

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  6. Wow. FINALLY someone who knows what they are talking about! Wonderful site! I too have developed insulin resistance as a result of eating a vegan diet. Keep spreading the word. People need to know the truth.

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  7. Anonymous9:46 PM

    I don't understand. Couldn't these women have prevented a B-12 deficiency simply by taking a daily vitamin/supplement while still following their diet of choice? Prenatal vitamins should provide all the B-12 expecting mothers need, shouldn't they?

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  8. It seems to be that there's a significant difference between rural villagers in India and those who chose to practice vegetarian diets in the West. The latter tend to be of high socio-economic status and therefore have access to vitamin supplements, a variety of foods, and presumably a greater awareness of nutritional requirements.

    This study does not suggest that it is the mother’s vegetarian diet per se that causes increased insulin resistance and visceral adiposity in children – it’s the vitamin B12 deficiency, which is easily remedied through supplementation. Also, as the authors note, the study is limited by the fact that it is an observational study and cannot establish causality or adjust for all other factors that might affect the results. Finally, it does not specify exactly what foods the mothers were eating, beyond the macro-nutrient profile – a diet of potatoes and rice obviously would be inferior to one based on beans, nuts and seeds and leafy greens.

    By the way -- echo K Dill's comments about dietary differences. Studies show that LO vegetarians and fish-eaters outlive their meat-eating counterparts but that vegans are on par with or below meat-eaters in longevity.

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  9. It seems to me that there's a significant difference between rural villagers in India and those who chose to practice vegetarian diets in the West. The latter tend to be of high socio-economic status and therefore have access to vitamin supplements, a variety of foods, and presumably a greater awareness of nutritional requirements.

    This study does not suggest that it is the mother’s vegetarian diet per se that causes increased insulin resistance and visceral adiposity in children – it’s the vitamin B12 deficiency, which is easily remedied through supplementation. Also, as the authors note, the study is limited by the fact that it is an observational study and cannot establish causality or adjust for all other factors that might affect the results. Finally, the article does not specify exactly what foods the mothers were eating, beyond the macro-nutrient profile – a diet of potatoes and rice obviously would be inferior to one based on beans, nuts and seeds and leafy greens.

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  10. Well said, DollyHaze! I have been vegan for 4 1/2 years, I'm 44 years old and I got pregnant with baby # 4 at age 42.
    We have a well balanced, nutritioulsy sound diet, all of us, including my baby, who at age 14 months is still getting mama's milk, just like her siblings did.

    I would say that the study should have a comparative counterpart following women and babies in some place where all they eat is animal proteins and see what kind of problems this children develop, what kind of "high risk" they have!

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  11. Very important for the mother to prepare a Pregnancy Diet chart for herself. The mothers are advised to follow the diet during pregnancy..thanks for sharing the information through your post...

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