Most comprehensive review yet of keto diets finds heart risks, cancer risk, dangers to pregnant women and kidney patients

WASHINGTON—In the most comprehensive analysis yet of ketogenic (keto) diets, a review in Frontiers in Nutrition finds keto diets place pregnant women and kidney disease patients at risk of adverse health effects. The review, Ketogenic Diets and Chronic Disease: Weighing the Benefits Against the Risks, also found that for most people, the possible long-term risks of the keto diet, including heart disease, cancer, diabetes, and Alzheimer's disease, outweigh its possible benefits.

“The typical keto diet is a disease-promoting disaster,” says lead review author Lee Crosby, RD, nutrition education program manager at Physicians Committee for Responsible Medicine. “Loading up on red meat, processed meat, and saturated fat and restricting carbohydrate-rich vegetables, fruits, legumes, and whole grains is a recipe for bad health.”

Five key findings of the Frontiers in Nutrition review paper are:

1. Keto diets may be especially unsafe for women who are pregnant or may become pregnant—low-carb diets are linked to a higher risk of neural tube defects in the baby, even when women take folic acid.
2. Higher-protein keto diets could hasten kidney failure in those with kidney disease.
3. Keto diets raise “bad cholesterol” levels for many patients.
4. Keto diets are presented as a panacea, but they are not likely to be safe long term.
5. Restricting carbohydrate skews the diet toward cancer-causing foods. In fact, typical keto foods have been linked to an increased risk of heart disease, cancer, diabetes, and Alzheimer's—often the very diseases they are touted to help.

The term “ketogenic diet” generally refers to a diet that is very low in carbohydrate, modest in protein, and high in fat. This mix of fuels aims to induce ketosis, or the production of ketone bodies that serve as an alternate energy source for neurons and other cell types that cannot directly metabolize fatty acids.

Keto diets have been promoted for weight loss and, less commonly, for other health reasons—seizure disorders, obesity and weight management, type 1 and type 2 diabetes, fatty liver disease, cancer, Alzheimer’s disease, heart disease, kidney health, and prepregnancy and pregnancy—all of which were considered in this review. It also looked at potential long-term effects on health.

“In addition to the significant risks to kidney disease patients and pregnant women, keto diets are risky for others, too, as these diets can increase LDL cholesterol levels and may increase overall chronic disease risk,” Crosby explains. “While keto can reduce body weight short term, this approach is not more effective than other weight-loss diets.”

Researchers found that the only well-supported use for this dietary approach is to reduce seizure frequency in some individuals with drug-resistant epilepsy.

Crosby conducted the review with colleagues from New York University’s Grossman School of Medicine; New York City Health and Hospital at Bellevue; University of Pennsylvania; Loma Linda University; and George Washington University School of Medicine.

Founded in 1985, the Physicians Committee for Responsible Medicine is a nonprofit organization that promotes preventive medicine, conducts clinical research, and encourages higher standards for ethics and effectiveness in education and research.

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