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Low carb diet risky when pregnant
Women who are pregnant or planning to become pregnant may want to avoid dieting that reduces or eliminates carbohydrates, as this could increase their risk of having babies with neural tube birth defects. According to a new study from the University of North Carolina at Chapel Hill, the fortified folic acid in U.S. carbohydrates defends neural tube development in fetal growth. The work is published in the journal Birth Defects Research.
Data analysis found women with low carbohydrate intake are 30 percent more likely to have babies with neural tube defects such as spina bifida (malformations of the spine and spinal cord) and anencephaly (absence of major portions of the brain and skull), that can lead to lifelong disability and infant death, as compared to women who do not restrict their carbohydrate intake. This is the first study to evaluate the relationship between low carbohydrate intake and children with neural tube defects.
The data analyzed was from the National Birth Defects Prevention Study, and spanned 1998-2011 including 11,285 pregnant women from Arkansas, California, Georgia, Iowa, Massachusetts, New York, North Carolina, Texas and Utah. Of these women, 1,740 had infants, stillbirths or terminations with anencephaly or spina bifida while 9,545 had live born infants without birth defects.
"We already know that maternal diet before and during early pregnancy plays a significant role in fetal development. 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," said Tania Desrosiers, PhD, MPH, and research assistant professor of epidemiology at the UNC Gillings School of Global Public Health, who led the study. "This finding reinforces the importance for women who may become pregnant to talk to their health care provider about any special diets or eating behaviors they routinely practice."
Folic acid is an essential nutrient that minimizes risk of neural tube defects. More than 20 percent of women in the U.S. have blood folate concentrations below the recommended level to reduce risk of this deformity.
For this reason, in 1998 the Food and Drug Administration began requiring folic acid be added to enriched grain products. Desrosiers and her study collaborators found dietary intake of folic acid among women with restricted carbohydrate diets was less than half of other women.
The Centers for Disease Control and Prevention recommends that all women who may become pregnant take a daily multivitamin with at least 400 micrograms of folic acid every day before and during pregnancy. However, as almost half of all pregnancies in the U.S. are unplanned, many women don't initiate folic acid supplements until later in pregnancy, after a neural tube defect may have occurred. This makes fortified foods an important source of folic acid for women who may become pregnant.
Folic acid fortification significantly reduced the prevalence of neural tube defects (NTDs) in the United States. The popularity of “low carb” diets raises concern that women who intentionally avoid carbohydrates, thereby consuming fewer fortified foods, may not have adequate dietary intake of folic acid.
To assess the association between carbohydrate intake and NTDs, we analyzed data from the National Birth Defects Prevention Study from 1,740 mothers of infants, stillbirths, and terminations with anencephaly or spina bifida (cases), and 9,545 mothers of live born infants without a birth defect (controls) conceived between 1998 and 2011. Carbohydrate and folic acid intake before conception were estimated from food frequency questionnaire responses. Restricted carbohydrate intake was defined as <=5th percentile among controls. Odds ratios were estimated with logistic regression and adjusted for maternal race/ethnicity, education, alcohol use, folic acid supplement use, study center, and caloric intake.
Mean dietary intake of folic acid among women with restricted carbohydrate intake was less than half that of other women (p < .01), and women with restricted carbohydrate intake were slightly more likely to have an infant with an NTD (AOR = 1.30, 95% CI: 1.02, 1.67).
This is the first study to examine the association between carbohydrate intake and NTDs among pregnancies conceived postfortification. We found that women with restricted carbohydrate intake were 30% more likely to have an infant with anencephaly or spina bifida. However, more research is needed to understand the pathways by which restricted carbohydrate intake might increase the risk of NTDs.
Authors: Desrosiers collaborated with Anna Maria Siega Riz PhD, former professor of epidemiology and nutrition at UNC Gillings School of Global Public Health and now Associate Dean for Nursing, University of Virginia; Robert Meyer PhD, Adjunct Professor, Maternal and Child Health, UNC Gillings School of Global Public Health; and Bridget Mosely MS, University of Colorado Hospital.
Further investigation needs to be done to replicate these findings in other study populations, as well as to better understand the mechanisms underlying the relationship between carbohydrate intake and neural tube defects.
This study was supported by grants from FAPESP (CEPID number 2013/08028-1 and INCT number 14/50931-3 to M.Z. and Thematic grant number 2014/03620-2 to S.V.-A.) and CNPq (INCT number 465355/2014-5 to M.Z.); Luiz Carlos de Caires Júnior is a fellow of FAPESP (2017/16283-2); Ernesto Goulart is a fellow of FAPESP (2015/14821-1); Bruno Araujo is a fellow of FAPESP (2014/08049-1); Vanessa van der Linden Mota is supported by AACD (Recife – PE); Joăo Ricardo de Oliveira is supported by CNPq (440770/2016-5). We are extremely grateful to Dr. S. Raia, D. Bertola, M. Vibranoski, P. Cunha, E.L. Durigon, W. Cumpady, P. Zanotto, C.R.S. Maia, A.N. Melo, M.T.A.L. Bezerra, D.A.M. de Araújo, A. Tanuri, R.S. de Aguiar, and T.R. Gollop for scientific discussions and sample collections. L. Suzuki and E. Amaro-Júnior for helping with CT analysis. N. Lourenço, and M. Aguena for technical support in exome sequencing and MLPA assay.
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In the first study of an association between carbohydrate intake and neural tube defects (NTDs) in pregnancies conceived after breads became fortified with folic acid, science finds women who restrict carbohydrates in their diet were 30% more likely to have an infant with anencephaly or spina bifida.
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