In an open discussion with other experts on diabetes and diet, he added that the science is not controversial but policy regarding dietary control in diabetes is.
Speaking at a symposium at the European Association for the Study of Diabetes 45th Annual Meeting, Prof. Feinman said that official boards were reluctant to fully accept data supporting the role of carbohydrates in diabetes control and that scientists representing research in the field of low-carbohydrate diets and diabetes are underrepresented on policy panels.
“The recommendations are for relatively high carbohydrates. When you press the ADA [American Diabetes Association] for their recommendations, they say they do not have a specific diet, but in fact they recommend a high-carbohydrate [diet] and give grudging support to a restricted-carbohydrate diet.”
“I’d really like to see an impartial panel of scientists that doesn’t necessarily have any commitment to nutrition, [such as] physicists or meteorologists. The goal would be a clearer analysis of the facts, laying out the options, especially for people with diabetes. Let the patient and the physician make the decision,” he asserted.
Also speaking at the meeting, Arne Astrup, MD, head of the Department of Nutrition at the University of Copenhagen in Denmark, explained that ADA recommendations are an ongoing process and should not change every time a new study is published. “If you stick to evidence-based principles, you wouldn’t jump into new extreme diets. I think the ADA is correct in being conservative. It’s completely unsubstantiated that a very-low-carbohydrate diet is safe and effective in the long term. We need 2- to 4-year studies to show that this is more effective than other existing trials, such as the Diabetes Prevention Program trial and the Finnish Diabetes Prevention Study.”
Dr. Astrup presented findings from the 8-country Diet, Obesity and Genes (Diogenes 8) European dietary intervention study, which showed that, of the 548 people in the trial, those given the high-protein diet after weight loss maintained their weight loss most successfully. The study compared a high-protein diet with a low-glycemic-index diet, for which weight maintenance was less marked. “We kept fat content constant but increased protein slightly. We reduced carbohydrates slightly, from the normal 55% of calories to 45%, but . . . 20% is much lower. Also, we found that if the carbohydrates are consumed as high fiber and whole grains (low glycemic index), they add some benefit to the increased protein content.”
He added that the Diogenes 8 study would be most useful for weight maintenance after weight loss, and probably also weight-gain prevention. “We didn’t test diabetics but it is also likely that this diet would be as effective for Type 2 diabetics as other diets. In contrast to the very restrictive low-carbohydrate diet, this is actually a very safe diet, not a crash diet, because it provides all the nutrients with little risk at the end of the day.”
In contrast, Prof. Feinman suggested that a carbohydrate intake of around 20% is most effective in diabetes. However, there is a prevailing concern that low-carbohydrate diets cause people to eat more fat, which has implications for cardiovascular disease (CVD).
Prof. Feinman made the case that this is not an issue. “Keeping carbohydrates low would actually reduce the risk of CVD. In essence, fat in the presence of carbohydrate is where we find the problems, which is very different from fat in the absence of carbohydrate.”
He explained that carbohydrates, either directly or through insulin, are control elements in the metabolism. “They determine the disposition of fat — whether stored for obesity or whether having an effect on lipoproteins and vasculature. The metabolic effect of reducing carbohydrates is that it predisposes to oxidizing the fat rather than storing it, and in diabetes specifically, it prevents the metabolic state of high glucose and high insulin, which is detrimental across the board.”
In presenting data initially reported by colleagues, including Mary Gannon, PhD, from the University of Minnesota in Minneapolis, Prof. Feinman discussed the effect of a low-carbohydrate diet (20% of calories) on blood glucose control in people with Type 2 diabetes. The results were compared with those obtained in the same people after 5 weeks on a control high-carbohydrate (55%) diet. The low-carbohydrate group showed a significant decrease in fasting glucose, to near normal, and a decrease in hemoglobin A1c. Significantly, the diets were designed so that patients did not gain or lose weight, indicating the benefit even in the absence of weight loss.
Discussing the pros and cons of different diets for diabetics, Dr. Astrup said that it depends on whether the patient is insulin-sensitive or insulin-resistant. “If someone is more insulin-resistant, they may benefit more from a low-carbohydrate diet, but for insulin-sensitive patients, it is probably better to follow the low-fat/high-carbohydrate diet that is more suitable for them.”
Agreeing with Prof. Feinman, Iris Shai, MD, from Ben-Gurion University in Beer-Sheva, Israel, added that several recent intervention studies, including the 2-year Dietary Randomized Control Trial (DIRECT), suggest that Mediterranean and low-carbohydrate diets are more beneficial than a low-fat diet in improving long-term glycemic control, triglycerides, high-density-lipoproteincholesterol, the total cholesterol/low-density-lipoproteincholesterol ratio, and weight.
“Within the first year, most Type 2 diabetic patients have their biggest chance to be adequately controlled by diet and physical activity alone and to delay the need for antihyperglycemic drug therapy.” As long as we succeed in tailoring an individual diet strategy to the patient (i.e., low fat/med to low carbohydrate), according to his or her preferences, goals, and diet history, the patient will more successfully adhere to his or her way of life. This means that one diet doesn’t fit all, she said.
The ADA made a breakthrough when releasing a careful statement in 2008 about the effectiveness and safety of low-carb diets out to 1 year, Dr. Shai said. “I believe that the growing evidence-based medicine will eventually change the current perception of the recommended low-fat/high-carb diet. [When] patients can stick to this diet, [it] could help some proportion of the diabetics, as it is a calorie-restricted diet,” she concluded.
Dr. Astrup’s study was financed by the European Commission and foods for the trial were provided by a wide range of companies. Prof. Feinman, Dr. Astrup, and Dr. Shai have disclosed no relevant financial relationships.
European Association for the Study of Diabetes (EASD) 45th Annual Meeting: Symposium Session S24. Presented on October 2, 2009.