PROTECTIVE EFFECT SEEN WITH FOLIC ACID
Our studies have contributed to the growing awareness that taking multivitamins containing folic acid around the time of conception reduces risk for neural tube defects.
|Overall, vitamin users had 35% lower risk, but college-educated women and Latina mothers had much less benefit than other groups.|
|Among women who did not take multivitamins, those consuming fortified cereal had lower risks. One bowl of vitamin-fortified cereal contains at least 0.1 milligrams of folic acid—25% of the daily level recommended for women of childbearing age.|
DELVING DEEPER INTO FOLIC ACID METABOLISM
Taking vitamins does not eliminate the risk for neural tube defects—why do some pregnancies benefit while others do not? The search to understand how supplements alter risk has has focused on a number of genes that influence the developing baby’s folic acid metabolism. Variant forms of these genes can lower folic acid levels, particularly if the mother does not take multivitamins containing folic acid. Among babies who inherited variant genes and whose mothers did not use multivitamins, we found:
|MTHFR: About 1 in 6 babies had the genetic type “TT” of methylenetetrahydrofolate reductase (MTHFR); this variant was more common in Latino infants. Babies with type “TT” had a modest increase in spina bifida risk.|
|Methionine synthase: The 15% of babies who carried an altered form of this gene did not have a higher risk for spina bifida.|
|FR-: We found no variation in the folate receptor alpha (FR-) gene, responsible for folic acid transport into cells.|
|BHMT: Babies who have variants of the BHMT/BHMT2 gene do not have a higher risk for oral clefts.|
OBESITY DOUBLES RISK
We found obese women had nearly 2 times higher risk for neural tube defects—a finding since replicated by the Program and other researchers. The association was more pronounced for spina bifida (open spine) than for anencephaly (absence of the brain).
Nutritional and other factors didn’t explain the study results:
|Folic acid intake: Women who were obese—whether or not they used vitamins—still had a greater risk than non-obese women for neural tube defects.|
|Weight reduction diets: Those who dieted in the months just before or after conception did not have a higher risk.|
|Diabetes: Mothers with insulin-dependent diabetes have greater risk for neural tube defects, but excluding diabetics from our analysis did not change results.|
Will losing weight eliminate the extra risk seen among obese women? Not necessarily. There may be an underlying factor-nutritional, metabolic or even genetic—linked to both obesity and neural tube defects; if so, weight loss alone might not correct this factor. We caution women to consult their physicians before attempting to lose weight; an unsupervised diet actually could increase risk by eliminating nutrients such as folic acid.
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