Higher quality diet associated with reduced risk of some birth defects

The authors state in background information that folic acid supplementation and food fortification has been effective in preventing neural tube defects, but folic acid does not prevent all birth defects. "Nutrition research on birth defects has tended to focus on one nutrient (or nutritional factor) at a time," the authors write. "However, the reality of nutrition is much more complex."

Suzan L. Carmichael, Ph.D., from Stanford University, Stanford, Calif., and colleagues used data from the National Birth Defects Prevention Study "to examine whether better maternal diet quality was associated with reduced risk for selected birth defects." The data were collected in 10 states from pregnant women with estimated due dates from October 1997 through December 2005. Information was collected via telephone interviews with 72 percent of case and 67 percent of control mothers. Included in the analysis were 936 cases with neural tube defects, 2,475 with orofacial clefts, and 6, 147 controls without birth defects. Mothers reported their food intake using a questionnaire. The researchers developed two diet quality indices that focused on overall diet quality based on the Mediterranean Diet (Mediterranean Diet Score or MDS) and the U.S. Department of Agriculture Food Guide Pyramid (Diet Quality Index or DQI).

"…Increasing diet quality based on either index was associated with reduced risks for the birth defects studied," the authors found. "Most mothers of controls [children without birth defects] were non-Hispanic white and had more than a high school education; 19 percent smoked, 38 percent drank alcohol, and 78 percent took folic-acid-containing supplements during early pregnancy; and 16 percent were obese," the authors report. "Women who were Hispanic had substantially higher values for the DQI and the MDS, whereas values were lower among women with less education and women who smoked, did not take supplements, or were obese…"

"Based on two diet quality indices, higher maternal diet quality in the year before pregnancy was associated with lower risk for neural tube defects and orofacial clefts. This finding persisted even after adjusting for multiple potential confounders such as maternal intake of vitamin/mineral supplements," the authors write. "These results suggest that dietary approaches could lead to further reduction in risks of major birth defects and complement existing efforts to fortify foods and encourage periconceptional multivitamin use," the authors conclude.

Editorial: The Importance of Food

In an accompanying editorial, David R. Jacobs, Jr., Ph.D., from the University of Minnesota, Minneapolis, and colleagues note that while maternal intake of folate is important for fetal development, recent studies suggest the supplemental folic acid may have adverse health effects on older adults.

"The importance of the findings of Carmichael et al lies in showing that women obtain benefit from the consumption of a high-quality diet, beyond the benefits derived through grain fortification. This raises the question of whether a high-quality diet alone may be sufficient to prevent NTDs (neural tube defects) -- a strategy that would also remove the potential harm from fortification."

"The lesson from the article by Carmichael et al is an important one: people, including women of childbearing age, should eat good food."

"Reduction of NTDs may be achievable by diet alone, at the same time reducing potential risk for other chronic diseases in the rest of the population."