By David Liu, PHD

Saturday July 28, 2012 (foodconsumer.org) -- Eating high glycemic index food or eating foods with high glycemic load may increase risk of a number of cancers, according to a study published July 25, 2012 in Annals of Oncology.

The study led by J. Hu of Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada in Ottawa, ON, Canada and colleagues found glycemic index was associated with risk of prostate cancer. This means that eating high dietary glycemic index food/diet, which contains often high amounts of sugars, may boost risk of  prostate cancer.

Also the study found men and women eating highest amounts of sugar or a diet with high glycemic load was associated with 28, 44 and 41 percent more likely to develop colorectal cancer, rectal cancer and pancreatic cancer, respectively.

The researchers set out to study the associations between glycemic index and glycemic load and risk of cancers among subjects including patients with stomach cancer, colon cancer, rectum cancer, liver cancer, pancreatic cancer, lung cancer, breast cancer, ovarian cancer, prostate cancer, testis cancer, kidney cancer, bladder cancer, brain cancer, non-Hodgekin's lymphomas, leukemia, multiple myelomas and 50,939 controls.

For the study, participants filled out a validated food frequency questionnaire covering dietary information on eating habits two years prior to their enrollment in the study.

Prostate cancer is the only malignancy among selected cancers that was positively associated with dietary glycemic index.  Colorectal cancer, rectal cancer and pancreatic cancer are the only cancers of the selected malignancies that are positively associated with dietary glycemic load.

The study findings suggest that eating too much simple carbohydrates or sugars that are too easy to release glucose and eating too much of a high glycemic index diet can boost risk of selected cancers.

Glycemic index indicates the easiness for a  food/diet to release glucose.  Simple sugars like glucose get directly into blood stream without going through a digestion process so they are foods of high glycemic index.    Glucose has a glycemic index of 100, which is often used as the standard.  Complex carbohydrates with lots of indigestible fibers or cellulose and starch release glucose slowly so they are foods of low glycemic index.

Low glycemic index foods (55 or less) include most fruits and vegetables; legumes; some whole, intact grains; nuts; tagatose; fructose; kidney beans; beets; chickpeas

Medium glycemic index foods (56–69) include whole wheat products, pita bread, basmati rice, grapes, sucrose, raisins, pumpernickel bread, cranberry juice, regular ice cream

High glycemic index foods (70 and above) include white bread, most white rices, corn flakes, extruded breakfast cereals, glucose, maltose, maltodextrins, white potato, pretzels.

Glycemic load is another concept.  It indicates how much glucose a food can release into the blood stream.  One unit of glycemic load is one gram of glucose.  For instance, banana gets a glycemic load of 11 per 100 gram serving, which means eating 100 grams of banana is equal to eating 10 grams of glucose.

The most obvious impact of sugars/carbohydrates is on the pancreas.  It is no wonder that eating a food with high glycemic load or a food with high glycemic index demands the pancreas to produce insulin and other hormones to handle the carbohydrates.