Saturday April 14, 2012 (foodconsumer.org) - Eating too much high calorie density (high glycemic index) carbohydrates such as table sugar or high fructose corn syrup, which are commonly used in processed food and beverages, may increase risk of breast cancer, according to a new study in the April 10, 2012 issue of Nutrition Metabolism and Cardiovascular Diseases.

But the abstract of the study report does not explain what type of carbohydrate is responsible for the increased breast cancer risk. It is previously known that eating too much calories, regardless of its source, and and simple sugars such as fructose and glucose may increase the risk of developing cancer.

The study led by S. Sieri of the National Cancer Institute in Milan Italy and colleagues found that those who eating a diet with high dietary glycemic load were 45 percent more likely to be diagnosed with breast cancer, compared to those who ate a low glycemic load diet.

According to the authors, theoretically, a high glycemic index or glycemic load diet may increase breast cancer risk, probably because high loads of carbohydrates boost the production of insulin-like growth factor (IGF), which is known to be associated with high risk of cancer. That is why eating too much sugar increases risk of cancer.

It is not just theoretically that eating too much sugar can increase risk of cancer.  Observational studies have also found evidence to suggest the link between sugar consumption and increased risk of cancers such as breast cancer.  But not all studies are consistent.

The Italian researchers wants to investigate the correlation between dietary glycemic index and glycemic load and breast cancer risk in the Italian section of the European Prospective Investigation into Cancer and Nutrition (EPIC). 
For the study, all study participants were women recruited between 1993 and 1998 from five areas: Varese and Turin (north Italy), Florence (central Italy), and Ragusa and Naples (south Italy).  Participants completed validated food frequency questionnaries to estimate the glycemic index or glycemic loads of their diets.

During the follow-up, 879 breast cancer cases were identified with 797 invasive and 82 in situ.

Although high dietary glycemic load was associated with increased breast cancer risk, dietary glycemic index and total carbohydrate had no influence on the risk.  The association was not affected by menopausal status or body mass index, meaning that it can affect both pre-and post-menopausal women and lean and obese women.

The researchers wrote “Our data indicate that, in a Mediterranean population characterized by traditionally high and varied carbohydrate intake, a diet high in GL plays a role in the development of breast cancer.”

One in eight women in the United States are expected to be diagnosed with breast cancer.  In 2012, breast cancer is expected to be found in 210,000 women and the disease will kill about 50,000 patients in the U.S. this year.

Breast cancer is largely a preventable disease.  Many things women can do or not do can help prevent or reduce the risk.

Remember that not all carbohydrates have a high glycemic index.  Those with sugar and high fructose corn syrup have a high glycemic load.

A high glycemic load diet is a diet that can raise blood sugar quickly after eating the diet.  The glycemic index of a food can also have an effect on the levels of blood sugar.  The glycemic load of a food is defined as the grams of available carbohydrtaes in the food times the food’s glycemic index devided by 100.

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By David Liu, PHD