Objective: Dietary intake of vitamin D and calcium may be related to risk of breast cancer, possibly by affecting mammographic density. However, the few studies that have evaluated the association between these nutrients and mammographic density in postmenopausal women have had inconsistent results.
Methods: We conducted a cross-sectional analysis in 808 participants of the Mammogram Density Ancillary Study of the Women's Health Initiative. Mammographic percent density was measured using baseline mammograms taken before randomization of participants in the intervention trials. Vitamin D and calcium intake was assessed with a validated food frequency questionnaire and an inventory of current supplement use, both completed at baseline.
Results: After adjustment for age, body mass index, regional solar irradiance, and other factors, we did not find a relationship between vitamin D or calcium intake and mammographic density. Mean mammographic percent densities in women reporting total vitamin D intakes of less than 100, 100 to 199, 200 to 399, 400 to 599, and 600 or greater IU/day were 5.8%, 10.4%, 6.2%, 3.8%, and 5.1%, respectively (P trend = 0.67). Results in women reporting a total calcium intake of less than 500, 500 to 749, 750 to 999, 1,000 to 1,199, and 1,200 or greater mg/day were 7.3%, 4.9%, 7.3%, 6.9%, and 7.11%, respectively (P trend = 0.51). We did not observe any effect modification by overall level of mammographic density or solar irradiance, but supplemental vitamin D use was associated with lower density in younger women (P interaction = 0.009).
Conclusions: These findings do not support a relationship between dietary vitamin D or calcium intake and mammographic density in postmenopausal women. Additional studies should explore these associations in women of different ages and in relation to serum vitamin D levels.
Dietary intakes of vitamin D and calcium were not associated with mammographic density in this cross-sectional study of postmenopausal women participating in the Mammogram Density Ancillary Study of the Women's Health Initiative.
From the 1University of Massachusetts, Amherst, MA; 2Harbor-UCLA Research and Education Institute, Torrance, CA; 3Brigham and Women's Hospital, Harvard Medical School, Boston, MA; 4Department of Social and Preventive Medicine, University at Buffalo, State University of New York, Buffalo, NY; 5Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle WA; 6College of Agriculture and Life Sciences, University of Arizona, Tucson, AZ; 7Albert Einstein College of Medicine, Bronx, NY; 8University of Oklahoma Health Sciences Center, College of Public Health, Oklahoma City, OK; 9School of Public Health, University of North Carolina, Chapel Hill, NC; 10University of Wisconsin School of Medicine, Madison, WI; and 11Department of Epidemiology, School of Public Health and Community Medicine, and Department of Medicine, School of Medicine, University of Washington, Seattle, WA.
Received December 17, 2009; revised and accepted April 1, 2010.
Funding/support: The Women's Health Initiative program is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health, US Department of Health and Human Services, through contracts N01WH22110, 24152, 32100-2, 32105-6, 32108-9, 32111-13, 32115, 32118-32119, 32122, 42107-26, 42129-32, and 44221. The Mammogram Density Ancillary Study was funded by the National Cancer Institute (CA7601704).
Financial disclosure/conflicts of interest: The University of North Carolina Breast Imaging Lab has contractual research agreements with General Electric, Sectra, VuComp, and Real Imaging.
Address correspondence to: Elizabeth R. Bertone-Johnson, ScD, University of Massachusetts, 409 Arnold House, 715 North Pleasant Street, Amherst, MA 01003-9304. E-mail: firstname.lastname@example.org