High-Glycemic Foods Linked to Colon Cancer
Insulin Resistance Linked to Diabetes May Promote Colon Tumor Growth
Problem Hard to Pinpoint
"It's hard to pinpoint the real impact of a high-glycemic load diet, because it varies on a number of things, such as how much the food is processed, how big is the meal, and what other foods are in the meal," she tells WebMD. "If you have large portions, for instance, that also raises blood sugars very quickly."
These other factors may explain why the largest and longest study to date -- tracking nearly 50,000 Canadian women for 16 years -- found no link between intake of high-glycemic foods and future risk of colon cancers. That study was published last June.
"Because there have been very few studies of this issue to date, it is too early to make a final decision regarding an association with glycemic load to colon cancer," says Paul Terry, PhD, of the National Institute of Environmental Health Sciences in North Carolina, who led that study. "But the results of this study are interesting."
In Liu's study, some 40,000 American women filled out detailed questionnaires about their eating habits and their rates of colorectal cancers were tracked for nearly eight years. Overall, women consuming the most high-glycemic foods were three times more likely to develop colon cancers, but some women observed had a sixfold risk.
Although there are exceptions -- potatoes, All-Bran cereal, and bananas, for instance, have a high-glycemic load. But most "whole" foods rich in fiber have a low-glycemic load and since they take longer to digest, are less likely to trigger insulin resistance.
"If one was to make recommendations, I'd say you should replace refined grains with whole grains, replace potatoes with other vegetables, and eat more nuts, which have a low-glycemic load," Liu tells WebMD. "It's hard to pinpoint whether it's the fiber per se, or the fact that foods that contain high fiber also have phytochemcials that also help in preventing colon cancer."