The diabetes diet controversy
Diet should be the first line of defense against diabetes, both type 1 and type 2. There is no dispute about this. But a war is being waged over what that diet should be. It is the diabetes diet war. The opposing forces in this war are the high-carbohydrate/low fat establishment, whose most prominent proponent is the American Diabetes Association, and the low-carbohydrate/high protein revolutionaries, whose most famous proponent is Dr. Richard Bernstein.
The evolution of dietary guidelines for diabetes
The recommended diet for diabetes has changed dramatically over the past 75 years. Before the discovery of insulin in 1921, diabetics were kept alive by starvation diets that contained very little carbohydrates. After insulin was discovered, starvation was no longer needed for survival. However, carbohydrates continued to be restricted to only 20 percent of energy because carbohydrates raise blood sugar levels. In 1950 the dietary guidelines were revised to a recommendation of 40 percent carbohydrates, 40 percent fat and 20 percent protein. This new recommendation reflected concern that high levels of protein might contribute to diabetic kidney disease. About 30 percent of diabetics develop kidney disease, and diabetes is the single greatest cause of kidney failure in the United States. In 1986 the guidelines were again revised to reduce the fat content of the diet to 30 percent. This change was made because of the high prevalence of cardiovascular disease in people with diabetes and because of the wish to bring dietary guidelines into agreement with those of the American Heart Association for prevention of coronary artery disease. More recently, the recommended protein intake for people with diabetes is 10-20 percent of total daily energy.
If dietary protein intake comprises 10-20 percent of total energy and if no more than 30 percent of energy is to come from fat, then the only thing left is carbohydrates; so 50-60 percent of the diet has to be carbohydrates by default.
The argument for a low-carbohydrate diet
Dr. Richard Bernstein recommends a low-carbohydrate diet that is in direct opposition to the recommendations of the ADA. His rationale for his diet is that carbohydrates must be kept to a minimum because they cause a rapid rise in blood sugar. Protein, on the other hand, is converted much more slowly to glucose and does not cause a rapid rise. He feels that fat is safe because it has no effect on blood sugar. He challenges the contention that high fat diets make people fat and raise cholesterol levels.
“The fallacy that eating fat will make you fat is about as scientifically logical as saying that eating tomatoes will turn you red,” Bernstein writes. “This is the kind of fallacious thinking behind the prevailing ‘wisdom’ which maintains there is an unavoidable link between dietary protein and fat and high serum cholesterol.”
He believes that carbohydrates not only raise blood sugar levels in people with diabetes, but raise cholesterol and triglyceride levels as well.
He writes, “The evidence is now simply overwhelming that elevated blood sugar is the major cause of high serum lipid levels among diabetics and more significantly, the major factor in the high rates of various heart and vascular diseases associated with diabetes. Many diabetics were put on low-fat diets for so many years, and yet their problems didn’t stop. It is only logical to look elsewhere, to elevated sugar and hyperinsulinemia, for the causes of what kills and disables so many us.”
It is precisely a high carbohydrate diet that causes elevated levels of blood sugar and insulin.
Dr. Bernstein also contends that it is high blood sugar and not dietary protein that is the culprit in diabetic nephropathy (kidney disease). He cites studies with diabetic rats: they develop diabetic nephropathy when high blood sugars are maintained. Then if dietary protein is increased, kidney destruction accelerates. But if sugar levels are normal, the rats never develop diabetic nephropathy, no matter how much protein they consume. Bernstein asserts that diabetic nephropathy does not occur if blood sugar is kept normal; that dietary protein does not cause diabetic nephropathy; and that dietary protein has no substantial effect upon the functioning of healthy kidneys. However, once major, irreversible kidney damage has occurred, dietary protein might accelerate that damage.
Bernstein cites many studies to support his assertions in his book, Dr. Bernstein’s Diabetes Solution. But the most convincing evidence in support of his theories is the story of his own struggle with diabetes and what he discovered from it. This will be the subject of next week’s article.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.