Diets that have a high "glycemic index" -- that is, they produce high blood sugar levels -- may increase the risk of breast cancer among postmenopausal women who've used hormone replacement therapy (HRT), study results suggest.

The link may be stronger among those who do not engage in vigorous physical activity.

Typically, high glycemic index diets include a lot of sugars and refined starches and carbohydrates, which produce a rapid rise in blood glucose levels.

"Given evidence of a positive association between (high insulin levels) and breast cancer risk, we felt it conceivable that this reflects an underlying association with high glycemic index diets," Dr. Stephanie A. Navarro Silvera from Albert Einstein College of Medicine in New York stated.

Silvera and her colleagues used data from a large group of 49,613 Canadian women to examine breast cancer risk in association with overall glycemic index and dietary carbohydrate and sugar intake.

During a follow-up period of 16 years, 1,461 women developed breast cancer.

In the overall study population, the risk of breast cancer was not related to glycemic index or sugar and total carbohydrate intake, the team reports in the International Journal of Cancer.

However, in postmenopausal women, diets with a high glycemic index raised the risk of breast cancer by 87 percent. In premenopausal women, such diets actually cut the risk by 22 percent.

The association between glycemic index and breast cancer risk in postmenopausal women was slightly stronger among women reporting no vigorous physical activity, among those with a history of HRT use, and among those of normal weight.

These results require confirmation in other studies, Silvera and colleagues emphasize in their report.

SOURCE: International Journal of Cancer, April 20, 2005.