High-carb diet may increase breast cancer risk

August 25, 2004 in Cancer Prevention, Nutrition Topics in the News, Women's Health

High-carb diet may increase breast cancer risk

A diet high in carbohydrates may be linked to an increased risk of breast cancer, researchers from Harvard Medical School in Boston report. In a study of Mexican women, those who consumed the highest percentage of carbohydrates - particularly sugars - were most likely to develop breast cancer.

The researchers noted that most of the elevated cancer risk was related to consumption of sugar and refined starches. There is already good reason to keep intakes of these low for the prevention of heart disease and type 2 diabetes.

The team compared 475 Mexico City women who had breast cancer with 1,391 female residents who had not been diagnosed with cancer. On average, participants got 57% of their total calories from carbohydrates, 28% from fat and 15% from protein.

Women whose diet contained the highest percentage of carbohydrates were more than twice as likely to have breast cancer as women who consumed the fewest carbohydrates.

The risk was increased even though the team accounted for other factors that can influence the risk of breast cancer, including age, total calorie intake, socioeconomic status, family history of breast cancer and the number of times a woman has given birth.

Sucrose (table sugar) was the carbohydrate most strongly associated with an increased risk of breast cancer. The association between sugar and breast cancer was stronger among women who had gone through menopause.

Carbohydrates may influence the risk of breast cancer by their effect on the body's insulin pathway, according to the researchers.

After a person eats starchy or sugary carbohydrates, blood sugar rises. This spike in glucose triggers the secretion of the sugar-processing hormone insulin. Elevated levels of insulin may in turn lead to increased levels of a protein called IGF-I, and recent research has shown that IGF-I may be related to an increased risk of breast cancer, particularly in premenopausal women.

The researchers point out that carbohydrates make up a high proportion of the Mexican diet. A recent survey found that urban Mexican women obtained an average of 64 percent of total calories from carbohydrates.

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