Glycemic Index and Heart Disease

From Science News
The New GI Tracks.(glycemic index and heart disease)
Author/s: Janet Raloff Issue: April 8, 2000

For preventing heart disease, diets that control insulin are all the buzz.

Two new tomes offering ways to diminish health complications of insulin resistance share the same title--Syndrome X--the medical name for a constellation of abnormalities that often develop in insulin-resistant individuals (SN: 9/16/89, p. 184). These include increases in blood pressure (SN: 10/14/89, p. 254), the length of time fats circulate in the blood, and the share of cholesterol residing in especially small, low-density lipoproteins (LDLs), which pose a potent heart-attack risk (SN: 9/21/96, p. 182). Syndrome X differs from diabetes in that the body can still produce enough insulin to cope with its elevated blood sugar.

Both books move away from the low-fat mantra that has pervaded major health guidelines for the general population during the past decade and campaign instead for limits on carbohydrates--sugary and starchy fare. The approaches to managing carbs, however, differ dramatically, reflecting a sharp dichotomy in the research community. One of the Syndrome X books, by Jack Challem (2000, John Wiley & Sons), recommends that people with this problem select fare with a low glycemic index (GI). In these foods, carbohydrates break down slowly in the digestive system to provide the blood glucose that powers cells. Challem and his coauthors reason that this sluggish digestion will keep blood-glucose concentrations fairly low, enabling the body to metabolize this sugar via a stable, moderate production of insulin. In the other new book with the same title (2000, Simon & Schuster), Stanford Medical School endocrinologist Gerald Reaven--who first defined syndrome X in 1988--asserts that the easiest way to maintain steady, moderate insulin concentrations is to keep body weight low, avoid bingeing on food, and steer clear of low-fat diets while limiting saturated fats. Indeed, he told SCIENCE NEWS, "the last thing I'd worry about is glycemic index."

Yet the term glycemic index is entering the public lexicon, not to mention medical symposia, health guidelines, and nutritional prescriptions. Fueling this interest is a rapidly growing body of research reporting tantalizing prospects for diets guided by the rate at which their carbohydrates are digested. Some researchers suggest that such diets can also foster weight loss (see sidebar) and perhaps even slow or prevent the development of type II diabetes. Although the authors of these studies are quick to acknowledge limitations in their data--often owing to small test groups or short trials of diets--many are enthusiastic about the potential health payoff from managing insulin via the diet, especially in people with no apparent risk factors for diabetes.

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