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High-carbohydrate diet may pose heart risks.

High-carbohydrate diet may pose heart risk

The so-called "prudent" diet advocated by the American Heart Association and the American Diabetes Association may boost the risk of heart disease for people with insulin resistance, some researchers argue. These scientists quickly point out that the public heath message to eat more carobhydrates and fewer fatty foods helps most poeple lower their risk of coronary artery disease, which kills more than 500,000 people in the United States each year. But they question the wisdom of a carbohydrate-heavy diet for insulin-resistant individuals, who have trouble processing carbohydrates.

"If you take people with this problem and give them a diet recommended by the American Heart Association or the American Diabetes Association, you're going to make those same [cardiovascular] risk factors worse," says Stanford's Gerald M. Reaven. Both groups recommend diets in which carbohydrates represent 50 to 60 percent of the total calories consumed -- a carbohydrate load that the insulin-resistant person can't utilize effectively, he maintains.

Adds Stanford diet researcher Ann M. Coulston, "When patients who have non-insulin-dependent diabetes are given this so-called 'good' diet, they have marked increases in triglycerides and a significant decrease in HDL cholesterol. And in patients with diabetes, a rise in triglycerides is associated with an increased risk of cardiovascular disease."

Coulston and her colleagues studied 12 Type II diabetics, giving them two different diets for six weeks each. In one diet, carbohydrates made up 40 percent of the calories; the other contained 60 percent carbohydrates, the amount recommended by the American Diabetes Association. Diabetics on the 60 percent diet experienced a 30 percent rise in serum triglyceride and a 9 percent decrease in HDL. Coulston reported these results last June at the American Diabetes Association meeting in Detroit.

The ideal diet for the insulin-resistant individual, she suggests, would contain 40 to 45 percent carbohydrates and 35 to 40 percent fats (mostly the monounsaturated or polyunsaturated variety), with 15 to 20 percent of calories derived from protein. That resembles what most people in the United States eat now, with one major exception: The total fat category would contain fewer saturated fats -- such as those from dairy products and red meats -- and more polyunsaturated and monounsaturated fats, such as safflower and olive oil.

Preliminary evidence suggests such a diet would help Type Ii diabetics lower their coronary risk. In the Sept. 29, 1988 NEW ENGLAND JOURNAL OF MEDICINE, Scott M. Grundy and his colleagues at the University of Texas Southwestern Medical Center in Dallas report that Type II diabetics given a diet containing 50 percent fat (33 percent monounsaturated fat) and 35 percent carbohydrates showed a 25 percent drop in their plasma triglyceride blood levels and a 13 percent increase in HDL cholesterol values, compared with diabetics on a 60 percent carbohydrate diet.

Grundy, Reaven and Coulston have yet to convince many of their colleagues of such advantages. Most clinicians still advise diabetic patients to eat a low-fat, high-carbohydrate diet.

Diabetes research Steven M. Haffner of the University of Texas Health Science Center at San Antonio says the lipid-lowering effects of Grundy's high-monounsaturated-fat diet may be temporary. And Sherman M. Holvey of the University of California, Los Angeles, points out that Coulston's and Grundy's studies involved only small numbers of patients.

"The consensus of the American Diabetes Association is that the high-fat diet that both Dr. Reaven and Dr. Grundy talk about still requires further study, says Holvey, who currently serves as persident of the association. If further research confirms their preliminary findings, he adds, the association will consider changing its dietary guidelines.

As for people with syndrome X (see main story), most scientists say they aren't convinced the disorder exists. Yet if researchers verify syndrome X, says Grundy, the diet high in monounsaturated fats might paradoxically help them lower their blood levels of artery-clogging lips.
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Author:Fackelmann, Kathy A.
Publication:Science News
Date:Sep 16, 1989
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