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Do Low-Carb Diets Help Diabetes?
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Small Study Shows Restricting Carbohydrates Reduces Need for Medications
March 15, 2006 -- Should people with type 2 diabetes follow very low carbohydrate diets? The American Diabetes Association (ADA) says "no", but a small study from Sweden suggests such a diet may be one of the best ways to manage the disease and reduce the need for medication.
In the study, 16 obese patients with type 2 diabetes followed a calorie- and carbohydrate-restricted diet for 22 months. Most showed continuing improvements in blood sugar that were independent of weight loss; the average daily dosage of insulin among the 11 insulin-dependent patients was cut in half.
"Many people are essentially cured of their [type 2] diabetes by low-carbohydrate diets, but that message is not getting out," says low-carb proponent and biochemistry professor Richard Feinman, PhD, of the SUNY Downstate Medical Center in Brooklyn, N.Y.
While agreeing that carbohydrate restriction helps people with type 2 diabetes control their blood sugar, ADA spokesman Nathaniel G. Clark, MD, tells WebMD that the ADA does not recommend very low-carb diets because patients find them too restrictive.
"We want to promote a diet that people can live with long-term," says Clark, who is vice president of clinical affairs and youth strategies for the ADA. "People who go on very low carbohydrate diets generally aren't able to stick with them for long periods of time."
Low-Calorie vs. Low-Fat
In the Swedish study, obese patients with type 2 diabetes were asked to follow two different low-calorie diets for 22 months.
Sixteen patients were told to restrict carbohydrates to just 20% of their total calorie intake, with carbohydrate consumption limited to vegetables and salads. Bread, pasta, potatoes, rice, and breakfast cereals were not allowed.
Fifteen more patients were asked to follow a low-fat diet, which had the same number of calories -- 1,800 calories-a-day for men and 1,600 for women. Carbohydrates made up as much as 60% of daily calories. (Seven of the 15 patients in this group switched to the low-carbohydrate diet before the study ended.)
Researchers Jorgen Vesti Nielsen and Eva Joensson reported that more patients in the low-carbohydrate group than the low-fat group lost weight. But after 22 months, most patients had gained back some of the weight they had lost at six months.
Dependence on the oral diabetes drugs metformin and sulfonylureas was reduced in one-fifth of the patients in the original low-carbohydrate arm of the study at six months; two patients had stopped taking them. It is not clear if these patients still had reduced dependency on medication at 22 months.
Pills vs. Diet
Feinman acknowledges that many patients cannot stick to very low carbohydrate diets. But he adds that for those who can, restricting carbs could mean a life free from insulin and diabetes drugs.
Feinman directs the Nutrition and Metabolism Society, a group founded in 2004 in part to further research on carbohydrate restriction. He is editor of the Society's journal Nutrition and Metabolism, in which the study appeared.
"Many patients would prefer taking a drug over changing their lifestyle, but that should be the patient's choice," he says. "Patients aren't being told that they can do with diet what they do with pills."
But Clark says diets that severely restrict carbohydrates are often high in fats and protein.
High-fat diets have been linked to cardiovascular disease and high-protein diets increase the risk of developing kidney disease. People with diabetes are at high risk for both diseases.
"If you restrict your carbohydrates to 20%, the other 80% of your calories have to come from somewhere," he says. "We know high-fat and high-protein diets pose a definite risk for diabetics."
Clark says people with diabetes, like everyone, should strive to eat a healthy, balanced diet that includes plenty of fruits and vegetables and limits fats and foods with little nutritional value.
The most important thing that most people with type 2 diabetes can do to improve their health is lose weight, he says. That means following a calorie-restricted diet they can live with.
"Diabetics definitely need to watch what they eat, but that is sound advice for everyone," Clark says.
SOURCES: Nielsen, J.V.Nutrition and Metabolism, June 14, 2006; online open access journal. Richard Feinman, PhD, professor of biochemistry, SUNY Downstate Medical Center, Brooklyn, N.Y. Nathaniel G. Clark, MD, vice president for clinical affairs and youth strategies, American Diabetes Association.
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