Glycemic Index Fails Again

[Guest guest]

In her team's study, published in the British Journal of Nutrition, there was no

association between high-GI eating habits and elevated blood sugar among 813

adults who were followed over 5 years. The findings, Mayer- said, reinforce

the notion that GI is " simply not a good index of how food impacts blood sugar. "

'Glycemic index' questioned as diet tool

By Amy Norton Wed Mar 15, 3:58 PM ET

NEW YORK (Reuters Health) - Weight- and health-conscious eaters may not find

much help in following the so-called low-GI diet, a new study suggests.

In recent years, researchers have taken to classifying carbohydrates based on

their GI, or glycemic index -- a measure of the effects of a given food on blood

sugar levels. High-GI foods, like white bread and potatoes, tend to produce a

quick surge in blood sugar, and some studies have suggested that diets heavy in

such foods can contribute to weight gain, diabetes and heart disease.

Books and Web sites espousing " low-GI " diets have followed suit.

But not all studies have found associations between high-GI foods and elevated

blood sugar and diabetes. One reason is that it's hard to translate lab findings

on glycemic index to the much more complicated realm of everyday eating,

according to Dr. Mayer-, the lead author of the new study.

One problem, she told Reuters Health, is that a food's GI is determined under

artificial conditions where a person eats the test food after a fast, then has

blood sugar tests taken two hours later. But a food has different blood sugar

effects when it's not eaten after a fast, she said.

In addition, many factors sway blood sugar levels after a meal, according to

Mayer-, a diabetes researcher at the University of South Carolina in

Columbia. These include the length of time a carbohydrate is cooked, the foods

it is eaten along with, and the workings of an individual's hormones, among

other things.

In her team's study, published in the British Journal of Nutrition, there was no

association between high-GI eating habits and elevated blood sugar among 813

adults who were followed over 5 years.

The findings, Mayer- said, reinforce the notion that GI is " simply not a

good index of how food impacts blood sugar. "

The health benefits that some studies have attributed to low-GI foods may

actually reflect other qualities of those foods - like high fiber content,

according to the researcher. Fiber-rich foods like whole grains are often lower

on the GI scale.

What's more, GI is a complicated way to judge a food's value. Certain

vegetables, for instance, have a fairly high GI, but actually contain very few

grams of carbohydrate and few calories. On the other hand, a dish of ice cream

may have a lower GI than a bowl of brown rice.

Mayer- said that in her view, health-conscious consumers should not bother

with seeking out the GI of their favorite foods.

The best move, she advised, is to keep calories in check and eat plenty of

fiber-rich whole grains, fruits, vegetables and beans - and to burn calories

through regular exercise.

Many studies, she noted, show that obesity is the " major player " in the risk of

diabetes, and weight control is essentially a matter of balancing calorie intake

with calorie expenditure through physical activity.

SOURCE: British Journal of Nutrition, February 2006.