A new study finds a link between low-carb diets and birth defects.
Neural tube defects (NTDs) are malformations of the brain, spine, and spinal cord. They develop before birth and include spina bifida, wherein the spinal column does not close completely, and anencephaly, wherein large portions of brain and skull are missing.
Research carried out over decades conclusively demonstrated that folic acid can reduce the risk of babies being born with NTDs.
Because folate massively decreases the risk of NTDs, the Food and Drug Administration (FDA) concluded that all grains and cereals should be enriched with 140 micrograms of folic acid per 100 grams of product by January 1998.
As soon as the fortification began, cases of birth defects plummeted. Adding folic acid to food prevents more than 1,300 NTD cases each year in the United States.
The rise of low-carb diets
Today, low-carb diets are increasingly popular. According to a recent study, this may be undoing much of the good work that folic acid fortification has done.
Restricting carbohydrate intake often means avoiding the food products that are fortified with folic acid, such as bread, cereal, and pasta. In fact, low-carb diets are associated with a reduced intake of a number of micronutrients.
Scientists from the University of North Carolina (UNC) at Chapel Hill hypothesized that "women who restrict carbohydrates may have suboptimal folate status and subsequently may be at higher risk of having an NTD-affected pregnancy." Their results were published earlier this month in the journal Birth Defects Research.
To test their hypothesis, the scientists took data from the National Birth Defects Prevention Study, which ran from 1998 to 2011. The dataset included 11,285 pregnant women from Arkansas, California, Georgia, Iowa, Massachusetts, New York, North Carolina, Texas, and Utah.
The scientists were led by Tania Desrosiers, Ph.D., a research assistant professor of epidemiology at the UNC Gillings School of Global Public Health. The study was funded by the Centers for Disease Control and Prevention (CDC).
Of the participants, 1,740 had "infants, stillbirths, and terminations with anencephaly or spina bifida." Folic acid and carbohydrate intake before conception were estimated using questionnaire data. The researchers also tracked race, alcohol consumption, and education, among other factors.
The risk of low-carb diets
After analysis, the researchers found that folic acid intake in women on low-carbohydrate diets was less than half of the other women. They were also significantly more likely to have an infant with NTD.
Overall, women on restricted carbohydrate diets were 30 percent more likely to have a child with an NTD than women who were not restricting their carb intake.
"We already know that maternal diet before and during early pregnancy plays a significant role in fetal development," says Desrosiers.
"What is new about this study is its suggestion that low carbohydrate intake could increase the risk of having a baby with a neural tube defect by 30 percent. This is concerning because low-carbohydrate diets are fairly popular."
Tania Desrosiers, Ph.D.
Although many women take folic acid supplements during pregnancy, these types of birth defects most commonly occur in the early phases of pregnancy. Because almost half of U.S. pregnancies are unplanned, by the time the pregnancy is discovered, it is often too late to prevent many NTD cases.
According to some other studies, more than 20 percent of U.S. women of child-bearing age have insufficient levels of folic acid.
Although the study included a large number of participants, there were certain shortfalls — such as relying on the womens' memories of what foods they had eaten before conception. Also, they could not directly measure folic acid levels with blood tests.
There are other conclusions that we could draw from these data. For instance, the authors mention that their findings might have been due to the caloric restriction involved in low-carb diets, or the overall quality of diet. As mentioned earlier, low-carb diets also restrict the intake of a range of micronutrients.
The researchers also mention a Californian study that concluded that "maternal dieting behaviors involving restricted food intake during the first trimester may be associated with increased NTD risk."
There is still much to learn on this topic, and because of the high stakes, the more knowledge we have, the better. It will take time to develop a clear understanding of the mechanisms involved.