Vitamin D and calcium intakes from food or supplements and mammographic breast density.
BACKGROUND
A better understanding of factors that affect breast density, one of the strongest breast cancer risk indicators, may provide important clues about breast cancer etiology and prevention. This study evaluates the association of vitamin D and calcium, from food and/or supplements, to breast density in premenopausal and postmenopausal women separately.


METHODS
A total of 777 premenopausal and 783 post-menopausal women recruited at two radiology clinics in Quebec City, Canada, in 2001 to 2002, completed a food frequency questionnaire to assess vitamin D and calcium. Breast density from screening mammograms was assessed using a computer-assisted method. Associations between vitamin D or calcium and breast density were evaluated using linear regression models. Adjusted means in breast density were assessed according to the combined daily intakes of the two nutrients using generalized linear models.


RESULTS
In premenopausal women, total intakes of vitamin D and calcium were inversely related to breast density (beta = -1.4; P = 0.004 for vitamin D; beta = -0.8; P = 0.0004 for calcium). In multivariate linear regression, simultaneous increments in daily total intakes of 400 IU vitamin D and 1,000 mg calcium were associated with an 8.5% (95% confidence interval, 1.8-15.1) lower mean breast density. The negative association between dietary vitamin D intake and breast density tended to be stronger at higher levels of calcium intake and vice versa. Among postmenopausal women, intakes of vitamin D and calcium were not associated with breast density.


CONCLUSIONS
These findings show that higher intakes of vitamin D and calcium from food and supplements are related to lower levels of breast density among premenopausal women. They suggest that increasing intakes of vitamin D and calcium may represent a safe and inexpensive strategy for breast cancer prevention.
Bérubé
Sylvie
S
Unité de recherche en santé des populations, Hôpital St-Sacrement du Centre hospitalier affilié universitaire de Québec, 1050 Chemin Sainte-Foy, Quebec, Quebec, Canada G1S 4L8.
Diorio
Caroline
C
Mâsse
Benoît
B
Hébert-Croteau
Nicole
N
Byrne
Celia
C
Côté
Gary
G
Pollak
Michael
M
Yaffe
Martin
M
Brisson
Jacques
J
D000328:Adult; D000368:Aged; D001940:Breast / Q000033:anatomy & histology / Q000187:drug effects*; D001943:Breast Neoplasms / Q000517:prevention & control*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000627:therapeutic use*; D015930:Diet Records; D005260:Female; D006801:Humans; D016014:Linear Models; D008327:Mammography; D008875:Middle Aged; D017698:Postmenopause; D017697:Premenopause; D014807:Vitamin D / Q000008:administration & dosage / Q000627:therapeutic use*
D002136:Calcium, Dietary; D014807:Vitamin D