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Oct. 26 (UPI) -- Eating a diet low in carbohydrates may help prevent Type 2 diabetes, lowering the blood sugar of people with unmedicated diabetes and people at risk for the disease that affecting more than 33 million Americans. That's the gist of new research led by Tulane University, which was published Wednesday in JAMA Network Open.
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Low-carb diets decrease hemoglobin A1c -- a marker for blood sugar levels -- in people with Type 2 diabetes at least as much as low-fat diets, the researchers said.
Yet, while doctors often recommend low-carb diets for people they treat for diabetes, evidence has been limited on whether eating fewer carbs can affect the blood sugar of people with diabetes or prediabetes who aren't treated by glucose-lowering medication.
Generally, a low-carb diet focuses on proteins and some non-starchy vegetables, while limiting grains, legumes, fruits, breads, sweets, pastas, starchy vegetables and fruit, according to the Mayo Clinic.
Non-starchy vegetables include asparagus, broccoli, eggplant, mushrooms and squash.
The Dietary Guidelines for Americans recommends that carbohydrates make up 45% to 65% of a person's total daily calorie intake: between 900 and 1,300 calories per 2,000 calories per day, the Mayo Clinic said.
By contrast, a daily limit of 0.7 ounce to 2 ounces, or 20 grams to 57 grams, of carbohydrates that provide 80 to 240 calories, is typical with a low-carb diet.
In the new study, the low-carb group's target was fewer than 40 net grams of carbohydrates during the first three months, and fewer than 60 net grams for months three through six.
The study involved about 150 participants, ages 40 to 70, whose blood sugar ranged from prediabetic to diabetic levels and who were not taking diabetes drugs.
The randomized clinical trial compared two groups: one assigned to a low-carb diet and another that continued with their usual diet. The low-carb group received dietary counseling.
After six months, members of the low-carb diet group had greater decreases in hemoglobin A1c, compared with those in the group who ate their usual diet. Their A1c levels fell 0.23% more than the usual diet group, which scientists described as modest but clinically relevant.
People in the low-carb diet group also lost weight and had lower fasting glucose levels, the scientists found.
Fats comprised roughly half of the calories eaten by people in the low-carb group, but the fats were mostly healthy monounsaturated and polyunsaturated fats found in foods such as olive oil and nuts, the researchers noted.
"The key message is that a low-carbohydrate diet, if maintained, might be a useful approach for preventing and treating Type 2 diabetes, though more research is needed," Kirsten S. Dorans, the study's lead author and assistant professor of epidemiology at Tulane University School of Public Health and Tropical Medicine, said in a news release.
The researchers noted that the study was unable to evaluate its effects independently of weight loss. Their paper concludes, "This diet, if sustained, might be a useful dietary approach for preventing and treating type 2 diabetes, but more research is needed."
The scientists said the study's findings are especially important for people with prediabetes whose A1c levels are higher than normal, but remain below levels that would be classified as diabetes.
According to the Centers for Disease Control and Prevention, roughly 96 million American adults -- or more than 1 in 3 -- have prediabetes. More than 80% of them are unaware of this condition, which also increases their risk of developing heart disease or stroke.
