Carbs Link to Less Common Breast Cancers
Postmenopausal women who eat a lot of breads and other carbohydrates may have an increased risk of the less common but deadlier forms of breast cancer, regardless of their weight, a recent study of European women suggests. The study was published last month in The American Journal of Clinical Nutrition.
Previous research is inconsistent on the link between carbohydrates and overall breast cancer risk, but this study may provide clues to the development of breast cancers that lack receptors for the hormones estrogen and progesterone. Tumors that do not have estrogen or progesterone receptors (ER-negative and PR-negative tumors) make up about a quarter of all breast cancers. These cancers are more challenging to treat and relatively more aggressive.
The study looked at the links between breast cancer risk and carbohydrates, glycemic load and glycemic index, which can all raise insulin. Glycemic index is a measure of how much a food raises blood sugar levels; the glycemic load takes into account the amount of food eaten and is generally considered a stronger indicator. The lower the glycemic load, the less it raises blood sugar and insulin levels.
Researchers in this study tracked the health of approximately 335,000 women who were part of the long-running study called the European Prospective Investigation into Cancer and Nutrition (EPIC). The women had completed questionnaires about what they ate and other relevant information at the start of the study.
After almost twelve years, the study found no link between any type of breast cancer and either carbohydrate consumption or glycemic load.
But when the researchers focused on postmenopausal women and specific forms of breast cancer they saw a link. Women who were in the highest categories of carbohydrate and glycemic load intake had an increased risk of ER-negative breast cancer. There was a slightly stronger link with ER-negative/PR-negative breast cancer.
The findings could indicate differences in how insulin affects the development of different breast cancers. It also may suggest genetic or other differences among the women who develop these types of breast cancers. More research is needed.
Source: Romieu I, et al. Dietary glycemic index and glycemic load and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC). Am J Clin Nutr. 2012 Aug;96(2):345-55. Epub 2012 Jul 3.