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Disclosures: Several of the authors are employed by or had received compensation from the Physicians Committee for Responsible Medicine, which funded the study. Please see the study for all authors’ relevant financial disclosures. Seres reports no relevant financial disclosures.
August 23, 2021
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Keto diets may cause ‘significant risks’ for pregnant women, physicians say

Source:

Press Release

Disclosures: Several of the authors are employed by or had received compensation from the Physicians Committee for Responsible Medicine, which funded the study. Please see the study for all authors’ relevant financial disclosures. Seres reports no relevant financial disclosures.
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Pregnant women on ketogenic diets may face greater risks for birth defects and gestational diabetes, according to a narrative review published in Frontiers in Nutrition.

However, a nutrition expert uninvolved with the research told Healio that the findings should be interpreted with caution, explaining that a narrative review opens the door to “a high risk of biased reporting.”

Crosby L, et al. Front Nutri. 2021;doi:10.3389/fnut.2021.702802.
Crosby L, et al. Front Nutri. 2021;doi:10.3389/fnut.2021.702802.

What the review showed

Keto diets are low in carbohydrates, modest in protein and high in fat. This mix of foods is designed to induce ketosis, which produces ketone bodies to serve as alternate energy sources for neurons and other cell types that cannot directly metabolize fatty acids.

Keto diets often are promoted for weight loss and sometimes for other health reasons, the researchers said, and following these diets may impact pregnancy.

Specifically, the authors cited the National Birth Defects Prevention Study (NBDPS), which found an association between low-carbohydrate diets consumed during the year before conception and an increased risk for birth defects. The infants of these women (daily carbohydrate intake 5th percentile of control mothers or 95 g of carbohydrates a day) were 30% more likely to have a neural tube defect (95% CI, 1.02-1.67), particularly anencephaly (OR = 1.35; 95% CI, 0.90-2.02) and spina bifida (OR = 1.28; 95% CI, 0.95-1.72). Women on carbohydrate-restricted diets with unplanned pregnancies specifically saw an 89% increased risk for neural tube defects (95% CI, 1.28-2.79). The NBDPS also found that folate supplement use may not mitigate the risks of low-carb diets, with “no effect measure modification,” according to the researchers.

Also, a 2019 study predating the use of folate-fortified grain products found increased neural tube defects among infants born to women who consumed low-carb diets before conception (OR = 2; 95% CI, 1.2-3.4), indicating other contributing factors.

The review additionally noted a prospective cohort study that evaluated gestational diabetes risk and scored women’s diets for adherence to a low-carbohydrate diet pattern and dietary fat source. According to this study, women who consumed the least carbohydrates had a 27% greater risk for gestational diabetes compared with those who consumed the most (RR = 1.27; 95% CI, 1.06-1.51; P = .03), after adjusting for BMI and other variables. The study also found a stronger association for women with a low-carb diet pattern high in animal products, seeing a 36% higher risk of gestational diabetes (RR = 1.36; 95% CI, 1.13-1.64; P = .003). But there was no association between increased risk and vegetable-based low-carb dietary patterns, the researchers said.

The authors of the review also associated some of the foods and dietary components commonly found in the keto diet — for example, red meat, processed meat and saturated fat — with increased risks for heart disease, cancer, diabetes and Alzheimer’s disease.

“Current evidence suggests that for most individuals, the risks of such diets outweigh the benefits,” they wrote.

David S. Seres, MD, ScM, PNS, FASPEN, section editor of UpToDate and a professor of medicine at the Institute of Human Nutrition, said the authors of the review “raise valid concerns,” but he questioned the quality of evidence on keto diets.

“Randomized studies of the effect of diet are difficult to do,” he said. “You would need a lot of people to agree to be randomly assigned to stay on keto diets long enough to see, for instance, how many heart attacks or how much cancer they have. Such a study may take hundreds if not thousands of subjects to adhere to the diet, likely for decades.”

Read Seres’ full commentary on the narrative review below.

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