Multivitamin Use and Mammographic Breast Density.

Background: The association of multivitamin use with mammographic breast density (MBD) is unclear, with 2 studies reporting conflicting findings.

Objectives: We aimed to investigate the associations of multivitamin use with volumetric measures of MBD-volumetric percent density (VPD), dense volume (DV), and nondense volume (NDV)-in a diverse population of women.

Methods: This cross-sectional study included 1083 women recruited during their annual screening mammograms at the Joanne Knight Breast Health Center, Washington University School of Medicine, St. Louis, MO. Participants were classified based on self-reported multivitamin use into nonusers, <1, 1-3, and 4-6 d/wk, and daily users. MBD was assessed as VPD, DV, and NDV using Volpara 1.5. Data were analyzed using general linear modeling and adjusted for potential confounders, including age, BMI, race, menopausal status, education, age at menarche, a family history of breast cancer, parity and age at first birth, oral contraceptive use, menopausal hormone therapy use, and alcohol intake. Statistical significance was set at P < 0.05.

Results: Multivitamin use was not associated with VPD. The adjusted mean VPD was 7.0% (95% CI: 6.6%, 7.2%) for nonusers, 7.1% (95% CI: 6.4%, 8.0%) for women who used multivitamins <1 d/wk, 7.4% (95% CI: 6.6%, 8.3%) for women who used multivitamins 1-3 d/wk, 7.1% (95% CI: 6.3%, 7.7%) for women who used multivitamins 4-6 d/wk, and 6.9% (95% CI: 6.6%, 7.3%) for daily users (P = 0.794). Similar null associations were observed between multivitamin use and DV and NDV. Race and menopausal status did not modify the associations.

Conclusions: There is no association between multivitamin use and MBD, regardless of the frequency of use. Studies evaluating the potential interactions among dietary patterns, specific nutrients, and MBD are needed to enhance our understanding of how dietary factors impact MBD.