The latest study to associate glycemic index with disease risk was published in the March issue of Cancer Epidemiology, Biomarkers and Prevention. The study involved 1,905 newly diagnosed lung cancer cases in non-Hispanic white people and a control group of 2,413 healthy non-Hispanic white people. The study found a higher “association” between people eating diets in the highest quintile (20%) of glycemic index and an increased risk of lung cancer.
Association and causation are not the same thing: association means that there’s a tendency for one factor to be linked to another but does not mean that one thing causes another, a point that is often misunderstood. For example, many heavy smokers who develop lung cancer tend to be coffee drinkers. Therefore, there’s an “association” between coffee and lung cancer cases but drinking coffee doesn’t “cause” lung cancer (smoking does) (REF: http://www.fasebj.org/content/29/1_Supplement/906.28.short).
The glycemic index has been used as a marker of carbohydrate quality since first being defined in the early 1980’s. Like many diet quality indexes, it falls far short of telling a complete story.
“The glycemic index has never been a reliable indicator of carbohydrate or diet quality,” notes Corrie Whisner, PhD, of Arizona State University. For example, higher glycemic index foods (including carrots, sweet potatoes, and whole wheat bread) have been associated with a reduced risk of disease. To exclude foods based only on their glycemic index alone would mean reducing important nutrients such as fiber and beta-carotene. In addition, the glycemic effect of specific foods like pasta or bread depends on the other meal components since these foods are not eaten alone. The amounts of protein and fat eaten with carbohydrates change the rate of absorption and glycemic load. Whisner noted, “An association between glycemic index and disease doesn’t tell the whole story which is probably more about what is missing in the diet (fiber, nutrients, fruits and vegetables, healthier fats, etc.) than what has been eaten.”
A better indicator of diet quality is following a food-oriented approach like the one suggested by MyPlate, the DASH diet or a Mediterranean Diet. All three of these dietary patterns have been shown to reduce overall chronic disease risk. In addition, when considering any dietary pattern or food, it’s important to realize that eliminating one type of food or group can have unintended consequences on the rest of the diet and the health of our gut bacteria. For example, if pasta is excluded from the diet, B vitamins, iron, fiber and folate are also reduced unless great care is taken to replace them with other foods. In addition, many people consume marinara (tomato sauce) and other vegetables with pasta, and this impacts risk of disease as well.
About the Wheat Foods Council
The Wheat Foods Council is a nonprofit organization formed in 1972 to help increase public awareness of grains, complex carbohydrates, and fiber as essential components of a healthful diet. The Council is supported voluntarily by wheat producers, millers, bakers, and related industries. For more information, visit the WFC website, www.wheatfoods.org.