Adolescent diet in relation to breast cancer risk among premenopausal women.

BACKGROUND: Although the association between adult diet and breast cancer has been investigated extensively, large prospective studies have generally not shown a direct link between intakes of carbohydrate, fat, fiber, and other nutrients and risk of breast cancer. Adolescence may be a period of increased susceptibility to risk factors that predispose to breast cancer. Dietary risk factors could therefore be more important during early life than later in adulthood.
METHODS: This is a prospective observational study of 39,268 premenopausal women in the Nurses' Health Study II who completed a 124-item food frequency questionnaire on their diet during high school (HS-FFQ) in 1998, at which time participants were 34 to 53 years of age. Cox proportional hazards regression was used to estimate relative risks and 95% CIs.
RESULTS: Four hundred fifty-five incident cases of invasive breast cancer were diagnosed between 1998 and 2005. Compared with women in the lowest quintile of intake, the relative risk of breast cancer in the highest quintile of adolescent total fat consumption was 1.35 (95% confidence interval, 1.00-1.81). Adolescent consumption of saturated, monounsaturated, polyunsaturated, and trans fats was not significantly associated with breast cancer risk. Total dairy, milk, carbohydrate intake, glycemic index, glycemic load, and fiber consumed during adolescence were not significantly related to breast cancer incidence.
CONCLUSION: Dietary fat consumed during adolescence may be associated with an elevated risk of breast cancer. Further studies to assess this relationship among postmenopausal women, and confirm these results in premenopausal women, are needed.