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Study on diet and birth defects has implications for all of us

Women who eat a low-fat, high-fiber diet rich in fruits and vegetables during the year before pregnancy have a significantly reduced risk of delivering a child with serious birth defects, a new study reports.

Specifically, the study found that women who ate the most healthful foods (essentially, a Mediterranean-type diet) before pregnancy were 36 percent to 51 percent less likely than those who ate the least healthful foods to give birth to a baby with anencephaly (a fatal disorder in which a large part of the infant’s brain and skull are missing) and 24 percent to 34 percent less likely to have an infant with a cleft lip.

David Jacobs
David Jacobs

The risk of spina bifida and cleft palate was also lower, but not as much as the risk for the other two birth defects.

The study, published Monday in the Archives of Pediatrics & Adolescent Medicine, also found that this apparent protection against birth defects occurred regardless of whether or not the women took vitamin and mineral supplements.

The Stanford University researchers who conducted the study believe this is the first large study to look at the association between a pregnant woman’s overall diet and birth defects.

These findings have implications that go beyond helping pregnant women give birth to healthier babies, however. For, as three epidemiologists at the University of Minnesota’s School of Public Health note in an editorial that accompanies the study, the findings raise “the question of whether a high-quality diet alone may be sufficient to prevent [birth defects] — a strategy that would also remove the potential harm for fortification.”

A fortification success story — with caveats
For more than a decade, the United States has been fortifying foods, particularly those made with refined grains, with the B vitamin folic acid to help ensure that women are not deficient in this nutrient early in their pregnancies, before they even know they’re pregnant. A deficiency of folic acid during the first few weeks of pregnancy can lead to the incomplete development of the fetus’ nervous system.

Refined (or non-whole-grained) foods were chosen to be fortified because they’ve been stripped of folic acid as well as other important nutrients during the refining process.

In terms of helping to prevent neural tube defects like anecephaly and spinal bifida, folic-acid fortification has been a resounding public-health success. But, as the U of M epidemiologists point out in their editorial, that strategy has also increased the amount of supplemental folic acid that everybody else gets. And that may be a public-health hazard.

“Every once in a while it looks as if some isolated supplement is working, but in general, the epidemiological evidence on isolated supplements is not what people had hoped,” said David R. Jacobs, one of the authors of the editorial, in a phone interview Monday.

Most of the evidence about the benefits and risks of taking isolated vitamins and minerals is either neutral or negative, he added.

And that’s true about folic-acid supplementation.

Randomized clinical trials have suggested that folic-acid supplementation — although beneficial to early fetuses — may increase the risk of cancer in adults.

“The B vitamins are very helpful in promoting growth,” Jacobs explained, “and cancer is something you would rather not grow.”

The importance of real food
The important take-home message from the Stanford study, said Jacobs, is that fetuses benefit from their mothers’ consumption of a high-quality diet — and that those benefits go beyond those derived through supplemental fortification.

“Foods are extremely highly nuanced,” he said. “Each consists of probably hundreds of thousands of substances.”

Relying on isolated vitamins or minerals, therefore, is not a replacement for real food — and in some cases, supplementation may be harmful.

“All of us, including pregnant women, should eat good food,” said Jacobs.

And what is good food?

“It’s not a bad idea when thinking about this to quote Michael Pollan: ‘Eat food, not too much, mostly plants.’ And I’d add to that, ‘[Eat] plants in colorful variety,’” said Jacobs.

Jacobs would also like to see more research into whether it is wise to supplement so much of our food supply with isolated nutrients.

“The biologic systems involved in nutrition and disease are complex and not completely understood,” he and his colleagues write in their editorial. “We do know, however, that the human body did not evolve in the presence of a fortified food supply, and that some of the healthiest populations on the planet subsist, even thrive, on a whole food diet. Thus, we feel that it is reasonable to call for further exploration of the health effects, whether positive or negative, of adding isolated compounds to the food supply.”

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