Serum 25-hydroxyvitamin D and mammographic density in premenopausal Spanish women.

• Most women have deficient serum 25(OH)D levels. • Lower mammographic density is observed among women with sufficient vitamin D levels. • The protective effect of vitamin D seems to be stronger for nulliparous women. The role of vitamin D in mammographic density is still unclear. This study examines the association between serum 25-hydroxyvitamin D (25(OH)D) and mammographic density, overall and by specific women characteristics. DDM-Madrid is a cross-sectional study that recruited 1403 premenopausal women in a breast radiodiagnosis unit of Madrid City Council. Information was collected with a questionnaire and plasma 25(OH)D was measured by solid-phase extraction on-line coupled to liquid chromatography–tandem mass spectrometry. Percent mammographic density was assessed using a semi-automated computer tool (DM-Scan). Multivariable linear regression models were used to quantify the associations, categorizing 25(OH)D levels (nmol/L) into 3 groups according to the cut-offs established by the US Endocrine Society. Models were adjusted for age, education, body mass index, age at menarche, parity, previous breast biopsies, family history of breast cancer, physical activity, energy intake, use of corticoids, hypercholesterolemia and day of sample extraction. Mean serum 25(OH)D level was 49.4 + 18.9 nmol/L. Women with sufficient concentrations of 25(OH)D showed a slight decrease in mammographic density (β >75nmol/L =-3.40; p = 0.037). No differences were observed according to women characteristics except for parity, where the protective effect of 25(OH)D was only seen among nulliparous (β >75nmol/L =-13.00; p-heterogeneity = 0.006). In light of the protective effect of vitamin D on mammographic density and the high prevalence of vitamin D insufficiency in our population, improving these levels could be an effective measure for the prevention of health problems related to the lack of this essential vitamin. [ABSTRACT FROM AUTHOR]