Caloric restriction reduces the risk of invasive breast cancer

Townsend Letter for Doctors and Patients, Oct, 2004 by Tori Hudson

This retrospective cohort study used data from 7,303 Swedish women with a history of hospitalization for anorexia nervosa prior to age 40. The incidence of breast cancer in these women was paired against the general risk for breast CA in the general Swedish female population.

Women hospitalized for anorexia prior to age 40 had a 53% lower incidence of breast CA. (95% CI, 3%-81%). Nulliparous anorexic women had a 23% (95% CI, 79% higher to 75% lower) lower incidence compared with nulliparous nonanorexic women, and parous women with anorexia had a 76% (95% CI, 13%-97%) lower incidence.

Commentary: We have known for many years that restriction of calories early in life in experimental animals, extends their lifespan and reduces tumor occurrence, including malignant breast tumors. It was not yet clear whether or not these findings would also hold true in humans, although obesity has been a clear risk factor for breast cancer.

Dietary associations with breast cancer risk have been confusing, especially the association between dietary fat and breast cancer risk. Although dietary fat is not necessarily related to caloric intake, it serves as a good marker for caloric intake. Perhaps the problem has been the investigation of adult diets rather than diets during youth. This has been part of the confusion with soy and breast cancer. The studies on soy and risk of breast cancer are much clearer for early exposure reducing the risk of breast cancer, but inconsistent regarding adult exposure.

While we of course, are not going to advocate for undernutrition and eating disorders, the message is clear that young girls should be educated about healthy nutrition, afforded the opportunity to have healthier food options, and be more aware of the dangers of high-caloric junk foods.

Michels KB, Ekbom A. Caloric restriction and incidence of breast cancer. JAMA 2004;291:1226-30.