A healthy diet plays an important role in cancer prevention and can help patients withstand rigorous cancer treatments. A recent analysis of data from the AARP Diet and Health Study, published in the American Journal of Epidemiology, suggested a very weak association among glycemic index, glycemic load, and risk of cancer

So What Exactly Are the Glycemic Index and Glycemic Load?
Sugar, or glucose, is our body's main source of energy. It comes from carbohydrates in food such as fruit, pasta, bread, and rice. Carbohydrates include fiber (which passes through the body), sugar, or starch, which your body breaks down and converts to sugar. Extra glucose is stored in the liver.

Glycemic index (GI) classifies carbohydrate-containing foods according to their potential to raise blood sugar levels. Foods with a low glycemic index raise blood glucose levels gradually. High glycemic foods, which may be associated with obesity, cause a rapid rise in blood sugar and excess insulin secretion. (Insulin in the hormone required for carbohydrate metabolism and regulating blood sugar levels.) Increased insulin levels and insulin-like growth factors are known to promote cellular growth and spread.

Nutrition experts rate carbohydrate-containing foods by GI on a scale of 1 to 100. Plain white bread, for example, has a high glycemic index. Raw apples, kidney beans, and lentils have a low glycemic index. You can find reference tables online that provide the GI index for many foods. Foods and beverages with a low GI help keep your blood sugar balanced and may reduce your risk for certain chronic diseases.

The glycemic load assesses the impact of carbohydrate consumption. The glycemic load considers not just the GI but also how much of that carbohydrate is in a serving of a specific food. Both affect blood sugar.

The Glycemic Index and Cancer Controversy
According to the National Cancer Institute, some studies suggest that low glycemic diets are associated with lower risks of certain cancers.

Joseph Mercola, MD, disagrees. He believes diets based on glycemic index do not effectively control blood sugar levels. He says numerous factors play a role in how specific foods will affect blood sugar. Furthermore, he says, look at fructose, a form of sugar found in foods such as fruit juices and honey: it is a low glycemic food, yet consumption of fructose is associated with being overweight.

Registered Dietitian Allison Massey advocates a diet that limits refined sugars and simple carbohydrates, and which contains more complex carbohydrates, such as whole grains. She says individuals can use glycemic load as a tool or guide for making better food choices.

Alison Massey, MS, RD, LDN, CDE reviewed this article.


National Cancer Institute. "Bridging Disciplines to Study Possible Cancer-Obesity Links." NCI Cancer Bulletin 8(22). Web. 15 November 2011.http://www.cancer.gov/ncicancerbulletin/111511/page5

Mercola, Joseph, MD. "Glycemic Index Deception Finally Understood." Web. 23 March 2006. http://articles.mercola.com/sites/articles/archive/2006/03/23/glycemic-index-deception-finally-understood.aspx

Chustecka, Zosia. "High-Carb Diet Increases Risk for Colon Cancer Recurrence." Medscape Medical News. Web. 7 November 2012. http://search.medscape.com/news-search?newSearchHeader=1&queryText=glycemic+load+and+cancer

George SM, Mayne ST, Leitzmann MF, et al. "Dietary Glycemic Index, Glycemic Load, and Risk of Cancer: A Prospective Cohort Study." American Journal of Epidemiology 169(4) (2009): 462-472. Web. 18 December 2008. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2726642/

Mayo Clinic. "Glycemic Index Diet: What's Behind the Claims." Web. 24 August 2011. http://www.mayoclinic.com/health/glycemic-index-diet/MY00770