In the longest-term study of its kind, researchers pitted two popular diets head to head a low-fat American Heart Associationstyle diet and a carb-controlled Mediterranean diet, each combined with regular physical activity in a population of overweight patients who had Type 2 diabetes.
Researchers found that over the four-year study, patients who adhered to the Mediterranean-style eating plan maintained lower blood-sugar levels for a longer time than those in the low-fat-diet group. On the basis of their findings, the study's authors suggest that some diabetes patients may be able to substitute diet and exercise for blood-sugar-lowering medications.
The study involved 215 overweight adults in Naples, Italy, who were newly diagnosed with Type 2 diabetes. Patients were randomly divided into two diet groups: the low-fat eaters were instructed to follow a regimen rich in whole grains, fruits and vegetables and low in additional fats, sweets and high-fat snacks; no more than 30% of daily calories were to come from fat and no more than 10% from saturated fat. The Mediterranean-diet group was taught to eat lots of fruits, vegetables, whole grains and healthy fats, including olive oil, with an emphasis on lean protein sources such as fish, chicken and nuts. Mediterranean dieters were instructed to limit carbohydrate intake to less than 50% of their daily calories.
All dieters were encouraged to exercise regularly and received regular nutrition counseling throughout the course of the study. Regardless of the specific eating plan, the study's participants were required to restrict their daily caloric intake: 1,800 calories maximum per day for men, and 1,500 calories daily for women a significant reduction from what the average American eats daily (about 2,600 calories for men and 1,800 calories for women, according to government statistics).
By the end of the study, which was published in the Sept. 1 issue of the Annals of Internal Medicine, 56% of patients following the Mediterranean diet were able to control their blood sugar without medication, compared with 30% of those on the low-fat regimen. The Mediterranean dieters were also able to maintain slightly more weight loss than the low-fat group 8.4 lb. vs. 7.1 lb. and showed small improvements in triglyceride and HDL cholesterol (the good kind) levels, both risk factors for heart disease.
"A Mediterranean-style diet is a very important part in the treatment of diabetes. We knew that," says Dr. Loren Greene, a New York University Medical Center endocrinologist, who was not involved in the study. "But there just hasn't been a good study to confirm this before." Some past studies have suggested that eating fewer carbohydrates can help diabetes patients lower their blood sugar. Other research has shown that intake of monounsaturated fats like olive oil can improve patients' insulin sensitivity, allowing the body to naturally control blood sugar more effectively.
The current study does not make clear, however, whether diet alone can reduce blood sugar enough to eliminate the use of diabetes medication or whether it is even advisable to forgo medication at all. Participants in the new study were kept off drugs when their A1C levels a measurement that indicates a patient's blood-sugar levels over the previous three months were below 7%, the standard cutoff for what is considered controlled blood sugar. But "we don't know for sure if people with A1C levels under 7% still need to be on drugs," says Greene. "The research just hasn't answered that question yet." Recent studies suggest that using blood-sugar-controlling medication even among the 57 million Americans who have prediabetes meaning they have elevated, but not dangerously high blood sugar and are at very high risk of developing diabetes may prevent the development of heart disease and stroke.
While diabetes doctors generally agree that the first line of defense against Type 2 diabetes should always be exercise and diet, many recommend also using drugs. For its part, the American Diabetes Association advises patients with Type 2 diabetes to make appropriate lifestyle changes and to start a drug regimen immediately upon diagnosis. Dr. R. Paul Robertson, a spokesperson for the organization, says that for people with diabetes, "the goal should not be to avoid drugs. It is to do everything you can to keep your sugar levels down."
Still, many doctors acknowledge patients' aversion to chronic drug-taking. "Almost universally, people don't want to take medicine if they can avoid it," says Greene. And physicians, including internist Dr. Christine Laine, who is the editor of the Annals of Internal Medicine, point out that the direct and indirect costs associated with taking a drug even one as widely prescribed as the generic diabetes medication metformin can serve as a barrier for many patients, especially among disadvantaged populations and those without health insurance.
Whether avoidance of medication in certain cases proves to be reasonable, for now it can at least be used as an effective incentive to improve lifestyle habits, says Greene: "If you are told, 'If you don't want to go on medicine, stick to this diet,' then that's a pretty valuable tool at least for patient compliance."