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!

A 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!