CUERNAVACA, Mexico--High carbohydrate diets were positively linked to increased incidence of breast cancer, according to a study published in the August issue of Cancer Epidemiology Biomarkers & Prevention (13, 8:1283-89, 2004) (www.cebp.aacrjournals.org).
The study conducted by the Instito Nacional de Salud Publica was a population-based case-controlled study involving 475 women aged 20 to 75 years with breast cancer (identified through six Mexico City hospitals) and a comparison group of 1,391 healthy women from the Mexico City population.
Researchers administered a questionnaire relating to sociodemographic variables and potential risk factors for breast cancer including reproductive and lactation history and diet. The sample population showed a total energy intake comprised of 57 percent carbohydrates, 27.6 percent fat and 15.4 percent protein.
After adjusting for total energy intake and all potential confounding variables such as age, social economic status, family history of breast cancer and parity, the risk of breast cancer was 2.2 times higher in women in the highest quartile of total carbohydrate intake when compared to women in the lowest quartile. The association was present in both premenopausal and postmenopausal women.
Among carbohydrate components, the strongest associations were observed for sucrose and fructose. No association was observed with total fat intake; however, polyunsaturated fat was inversely associated with risk of breast cancer, particularly among postmenopausal women.
The study also found dietary fiber intake may modulate the absorption of carbohydrates and can influence the glycemic response. The strength of the association between sucrose intake and risk of breast cancer was lower among women in the highest tertile of insoluble fiber intake when compared with women in the lowest tertile of insoluble fiber intake. The relative risk of breast cancer in the highest quartile of sucrose intake was 2.37 among women who consumed low levels of insoluble fibers (<22 g/d) and was 1.07 among women who consumed high levels of insoluble fibers (>22 g/d). Similar results were observed for fructose and glucose intakes.
The researchers concluded in this population a high percentage of calories from carbohydrate--but not from fat--was associated with increased breast cancer risk. This relationship deserves further investigation, the researchers noted, particularly in populations highly susceptible to insulin resistance.
