Mediterranean Diet and Breast Density in the Minnesota Breast Cancer Family Study

Abstract

Mediterranean populations' lower breast cancer incidence has been attributed to a traditional Mediterranean diet, but few studies have quantified Mediterranean dietary pattern intake in relation to breast cancer. We examined the association of a Mediterranean diet scale (MDS) with mammographic breast density as a surrogate marker for breast cancer risk. Participants completed a dietary questionnaire and provided screening mammograms for breast density assessment using a computer-assisted method. Among 1,286 women, MDS was not clearly associated with percent density in multivariate linear regression analyses. Because of previous work suggesting dietary effects limited to smokers, we conducted stratified analyses and found MDS and percent density to be significantly, inversely associated among current smokers (β = −1.68, P = 0.002) but not among nonsmokers (β = −0.08, P = 0.72; P for interaction = 0.008). Our results confirm a previous suggestion that selected dietary patterns may be protective primarily in the presence of procarcinogenic compounds such as those found in tobacco smoke.

ACKNOWLEDGMENTS

The authors thank Ms. Fang-Fang Wu for her work in reading mammograms and estimation of mammographic percent density. This work was supported by Grant 5 R03 CA097779-02 from the National Institutes of Health.

Notes

^a Abbreviations are as follows: BMI, body mass index; WHR, waist-to-hip ratio.

^b Number of MDS categories (out of 9) for which the subject was assigned a positive value.

^c Betas represent absolute estimated mean change in percent breast density per unit increment in continuous variables (age, BMI, age at menarche, dietary intake) but per 0.1 increment in WHR. For nominally coded predictor variables, betas represent absolute mean change in percent breast density relative to referent category. Associations with age are unadjusted, whereas all other associations are adjusted for age.

^d P < 0.0001, assessing the association between Mediterranean diet score and covariates; P values were determined by Cochran-Mantel-Haenszel test statistic for categorical variables or by analysis of variance of continuous variables.

^e P < 0.01.

^f P < 0.05.

^a Abbreviations are as follows: BMI, body mass index; WHR, waist-to-hip ratio. Betas adjusted for age, total energy intake, menopausal status, education, years of use of hormone replacement, BMI, WHR, age at menarche, parity and age at first live birth (combined variable), alcohol intake, and relation to proband. Betas represent absolute estimated mean change in percent breast density per unit increment in continuous MDS or absolute estimated mean change in percent density relative to 0–3 category for categorized MDS.

^b Revised so that for alcohol component of MDS, individual receives a score of 1 for 0 g/day of alcohol rather than for 5–25 g/day as in original scale and a score of 0 otherwise.

^a N = 176. Abbreviations are as follows: BMI, body mass index; WHR, waist-to-hip ratio. Betas adjusted for age, total energy intake, menopausal status, education, years of use of hormone replacement, BMI, WHR, age at menarche, parity and age at first live birth (combined variable), and relation to proband. All models except for alcohol additionally adjusted for alcohol intake.

^b Betas represent absolute estimated mean change in percent breast density for above vs. below median for all items except alcohol. Beta for alcohol represents absolute estimated mean change in percent density for intake of 5–25 g/day vs. all others.