Adolescent dietary vitamin D and sun exposure in relation to benign breast disease.

Purpose: Vitamin D may reduce cell proliferation and tumor growth in breast tissue, and exposure may be most important during adolescence when breast tissue is developing. In the Nurses' Health Study II, higher recalled adolescent vitamin D intake was associated with a lower risk of benign breast disease (BBD). Our study aimed to assess adolescent vitamin D exposure in relation to BBD in young women.

Methods: Vitamin D was assessed in 6,593 adolescent girls (9-15 years of age at baseline) in the prospective Growing Up Today Study cohort using the mean energy-adjusted intakes from food frequency questionnaires in 1996, 1997, and 1998. In 1999, 5,286 girls reported skin color, sunscreen use, tanning bed use, and number of sunburns in the past year, and we used state of residence to assess low versus high ultraviolet index. Biopsy-confirmed BBD was reported on questionnaires in 2005, 2007, and 2010 (n = 122).

Results: Dietary vitamin D, tanning behaviors, and other sun exposure variables were not significantly associated with BBD in logistic regression models adjusted for age, family history of breast cancer or BBD, age at menarche, nulliparity, alcohol intake, body mass index, and physical activity. The relative risk for the top (>467 IU/day) versus bottom (<243 IU/day) quartile of vitamin D intake was 0.76 (95 % CI 0.47, 1.23).

Conclusions: Sun exposure was not significantly associated with BBD in this prospective cohort. However, a suggestive inverse association between dietary vitamin D and BBD was observed that merits further study.