Folic Acid Does Not Prevent All Birth Defects, Overall Diet Quality Matters
When counseling pregnant women on a healthy diet, most physicians concentrate on education about the B vitamin folate. While fortification with folic acid in the diet has decreased the number of birth defects such as anencephaly and spina bifida, consumption of a single nutrient has not caused all birth defects to completely disappear. Scientists are now examining the quality of the overall pregnancy diet and how nutrients interact with one another to create a healthy baby.
Between October 1997 and December 2005, researchers with Stanford University School of Medicine asked women from 10 US states to answer detailed questions about their eating habits immediately before and during pregnancy. Just over 6,800 women had healthy infants, while 3,824 had babies with a neural tube defect or a cleft lip or palate. Using a scoring system that measured overall diet quality, the team scored the diets on how closely they matched the Mediterranean diet and the Dietary Guidelines for Americans, both of which emphasize fresh fruits and vegetables and healthy grains.
The women were classified into four comparison groups, ranked by diet scores. The women with the highest scores were 36-51% less likely to have a pregnancy affected by anencephaly. Similarly, the women with the best diets had 24-34% protection from cleft lip. The more healthy diets were also associated with lower instances of spina bifida and cleft palate, but the results were not as strongly correlated.
“Our study showed for the first time that the overall quality of the diet, and not just a single nutrient, matters in terms of reducing the risk of birth defects,” said Suzan Carmichael, PhD, an associate professor of pediatrics at Stanford.
“In the past, we’ve been trying to disentangle a particular nutrient from the composite diet. I think we're wrong in that approach,” adds Gary Shaw, DrPH, professor of pediatrics. “It would have been really nice to have the magic bullet against birth defects. Folic acid was the hope for a magic bullet, and it clearly made a difference, but only made some of the difference.”
A healthy diet protects the mother and baby not only by supplying a wide range of nutrients that work together for development, but also because it doesn’t leave a lot of room for junk foods which may have adverse effects.
It is also possible that a healthy diet is a marker for some other component of a mother’s lifestyle that protects against birth defects, notes the research team. For example, most mothers of healthy babies were well educated and fewer smoked, drank alcohol, or were obese. Future studies will further examine the relationship between diet quality and other pregnancy outcomes, including other types of birth defects.
In an editorial accompanying the study, Dr. David R. Jacobs Jr PhD, from the University of Minnesota, notes “The lesson from the article by Carmichael et al is an important one: people, including women of childbearing age, should eat good food.”
Arch Pediatr Adolesc Med. Published online October 3, 2011. doi:10.1001/archpediatrics.2011.185.
Arch Pediatr Adolesc Med. Published online October 3, 2011. doi: 10.1001/archpediatrics.2011.184