Article

Joint Effects of Dietary Vitamin D and Sun Exposure on Breast Cancer Risk: Results from the French E3N Cohort

Inserm, CESP Centre for Research in Epidemiology and Population Health, U1018, Nutrition, Hormones and Women's Health Team, F-94805, Villejuif, France.
Cancer Epidemiology Biomarkers & Prevention (Impact Factor: 4.13). 01/2011; 20(1):187-98. DOI: 10.1158/1055-9965.EPI-10-1039
Source: PubMed

ABSTRACT

Ecological studies have suggested that vitamin D production through ultraviolet (UV) solar irradiance could reduce breast cancer (BC) risk. Although studies restricted to dietary vitamin D intake have provided inconsistent results, little is known about the relationship between pre- and postmenopausal BC and combined intakes from diet, supplements, and sun exposure.
Cox proportional hazards regression models evaluated the association between vitamin D intakes, mean daily ultraviolet radiation dose (UVRd) at the place of residence and risk of BC among 67,721 women of the French E3N cohort. All analyses were stratified on menopausal status taking into account important confounders including calcium consumption.
During 10 years of follow-up, a total of 2,871 BC cases were diagnosed. Dietary and supplemental vitamin D intakes were not associated with BC risk; however, in regions with the highest UVRd, postmenopausal women with high dietary or supplemental vitamin D intake had a significantly lower BC risk as compared with women with the lowest vitamin D intake (HR = 0.68, 95% CI: 0.54-0.85, and HR = 0.57, 95% CI: 0.36-0.90, respectively).
Our results suggest that a threshold of vitamin D exposure from both sun and diet is required to prevent BC and this threshold is particularly difficult to reach in postmenopausal women at northern latitudes where quality of sunlight is too poor for adequate vitamin D production.
Prospective studies should further investigate associations between BC risk, vitamin D status and sunlight exposure.

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    • "With respect to endogenous synthesis of vitamin D3, small scale studies supported the concept that sunlight exposure is associated with reduced risk of breast cancer, however, the associations were dependent on region of residence and skin pigmentation (John et al., 1999, 2007). Larger international studies have consistently demonstrated significant inverse correlations between incident solar radiation and breast cancer rates (Edvardsen et al., 2011; Engel et al., 2011, 2014; Grant, 2013; van der Rhee et al., 2013). "
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    • "White women in our study had higher plasma 25(OH)D levels (means of 34.9 ng/mL in cases and of 37.4 in controls) compared to white women in previous nested case–control studies, with ranges from 20.0 to 31.5 ng/mL among cases and 20.4 to 33.1 ng/mL among controls [9-15,17,18]. This observation is consistent with findings from prospective studies of dietary vitamin D, sun exposure, and breast cancer risk in France [32] and in the United States [33] which showed a lower risk of breast cancer among women who were high dietary vitamin D consumers living in southern regions, but not in northern regions, of these countries. "
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    ABSTRACT: Higher sunlight exposure is correlated with lower incidence of breast cancer in ecological studies, but findings from prospective studies regarding the association of circulating levels of vitamin D with the risk of breast cancer have been null. The objective of this study was to examine the relation between plasma levels of vitamin D and the risk of postmenopausal breast cancer. We conducted a nested case-control study within the Multiethnic Cohort Study of five race/ethnic groups (white, African-American, Native Hawaiian, Japanese, and Latino) from Hawaii and Los Angeles between 2001 and 2006. Pre-diagnostic plasma levels of 25-hydroxyvitamin D2 [25(OH)D2], 25-hydroxyvitamin D3 [25(OH)D3] and 25(OH)D (sum of 25(OH)D2 and 25(OH)D3) were examined among 707 postmenopausal breast cancer cases and matched controls. Using conditional logistic regression models, 20 ng/mL increases of plasma 25(OH)D3 (odds ratio (OR) 0.28; 95% confidence interval (CI) 0.14-0.56) and 25(OH)D (OR 0.43; 95% CI 0.23-0.80) were inversely associated with breast cancer risk among white women, but not among women in other race/ethnic groups. Using two-segmented, piecewise-linear logistic regression models, the change-points of the ORs, either for 25(OH)D3 or for 25(OH)D, were detected as 20 ng/mL among whites. Circulating 25(OH)D3 and 25(OH)D were associated with a reduced risk of postmenopausal breast cancer among whites, but not in other ethnic groups, who reside in low latitude regions.
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    • "Thus, sunlight and other factors that affect circulating levels of 25(OH)D may influence cancer risk. Most cohort and case– control studies that have examined sunlight and/or ultraviolet light (UV) exposure—either through selfreported personal behaviors or via ambient levels at place of residence—have reported evidence of a negative association with breast cancer (Anderson et al. 2011b; Engel et al. 2011; John et al. 1999, 2007; Knight et al. 2007; Millen et al. 2009; Yang et al. 2011). "
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