Low-carb diet doesn't always cut diabetes risk after pregnancy

For women who develop diabetes during pregnancy, low-carbohydrate diets may not necessarily help keep the disease at bay after the baby arrives, a U.S. study suggests.

Researchers found that women eating diets high in animal proteins and low in carbs actually raised their diabetes risk. A low-carb diet that was heavy in plant-based protein and fat, in contrast, wasn’t linked to an increased risk of diabetes in the study.

“Our findings suggest that sources of protein and fats should be considered for a low-carb diet as a way to control blood sugar,” said lead study author Dr. Cuilin Zhang, a researcher at the National Institutes of Health in Rockville, Maryland.

The researchers focused on the risk of type 2 diabetes, which is linked to obesity and aging and happens when the body can’t properly use or make enough of the hormone insulin to convert blood sugar into energy.

All of the women in the study had a version of the disease while they were pregnant known as gestational diabetes, which usually disappears after delivery but significantly raises the future risk of developing type 2 diabetes.

That risk appears even higher for women who cut carbs and get most of their fats and proteins from red meat and other animal sources, the study found.

“Women with a history of gestational diabetes who follow a low-carbohydrate dietary pattern may consider consuming plant sources rather than animal sources of protein and fat to minimize their future risk of type 2 diabetes,” Zhang said by email.

To understand how diet influences future diabetes risk, Zhang and colleagues followed about 4,500 women with a history of gestational diabetes who filled out dietary surveys starting in 1991 and continuing every four years through 2001. Based on the results, they sorted the women into five groups from lowest to highest compliance with diets centered on reducing carbohydrates and boosting proteins.

Overall, women in the study with the highest compliance to the low-carb diet were 36 percent more likely to develop diabetes than those with the lowest adherence.

The researchers also scored the diets based on how much food came from animal versus plant sources.

The highest amounts of protein and fats from red meat and other animal sources were linked to a 40 percent greater diabetes risk than the lowest amounts, according to the results published in Diabetes Care.

Women were more likely to be overweight or obese with the highest amounts of meat in their diets, partly explaining their increased risk, the authors note.

By comparison, for women with the highest amounts of plant-based protein and fats in their diet, the increase in risk for diabetes small and might have been due to chance.

It’s possible that higher intake of dietary animal fat might make it harder for women to process sugar and increase their risk of diabetes, the researchers conclude.

Eating a meal rich in animal protein, compared to one heavy in protein from plants, may also lead to higher concentrations in the blood of branched-chain amino acids, protein building blocks that have been linked to an inability to process insulin and an increased diabetes risk, the authors speculate.

Women who ate the most animal-based protein and fat also tended to consume the highest amounts of red meat, a food tied to increased diabetes risk.

One limitation of the current study is that dietary surveys might not accurately reflect what women ate, the authors concede. It’s also possible that more health-conscious women who see the doctor more often are more likely to get a diabetes diagnosis.

Still, the findings emphasize that just because a diet is low-carb doesn’t make it healthy, said Dr. Deidre Tobias, an epidemiologist at Brigham and Women’s Hospital and Harvard University in Boston.

“A healthful combination of fruits, vegetables, whole grains, legumes, and perhaps some fish or lean protein can provide a flexible road map to overall high quality eating,” Tobias said by email.