Selenium (Se) is a trace mineral that has antioxidant and anti-inflammatory properties. This study aimed to investigate the association between Se intake, diabetes, all-cause and cause-specific mortality in a representative sample of US adults. Data from 18,932 adults who attended the 2003-2014 National Health and Nutrition Examination Survey (NHANES) were analysed. Information on mortality was obtained from the US mortality registry updated to 2015. Multivariable logistic regression and Cox regression were used. Cross-sectionally, Se intake was positively associated with diabetes. Comparing extreme quartiles of Se intake, the odds ratio (OR) for diabetes was 1.44 (95% CI: 1.09–1.89). During a mean of 6.6 years follow-up, there were 1627 death (312 CVD, 386 cancer). High intake of Se was associated with a lower risk of all-cause mortality. When comparing the highest with the lowest quartiles of Se intake, the hazard ratios (HRs) for all-cause, CVD mortality, cancer mortality and other mortality were: 0.77 (95% CI 0.59-1.01), 0.62 (95% CI, 0.35-1.13), 1.42 (95% CI, 0.78-2.58) and 0.60 (95% CI,0.40-0.80), respectively. The inverse association between Se intake and all-cause mortality was only found among white participants. In conclusion, Se intake was positively associated with diabetes but inversely associated with all-cause mortality. There was no interaction between Se intake and diabetes in relation to all-cause mortality.

The association between serum 25-hydroxyvitamin D [25(OH)D] concentration and breast cancer risk in postmenopausal women is not well understood. The aim of this study was to investigate the association between serum 25(OH)D concentration and breast cancer in postmenopausal women in the United States using nationally representative sample surveys. We used the data from seven cycles of National Health and Nutrition Examination Surveys from 2001 to 2014. Participants were non-institutionalized postmenopausal women (n = 8108). In restricted cubic spline analysis, a significant, nonlinear, invert ‘U’ relationship was observed between serum 25(OH)D concentrations and breast cancer in postmenopausal women (p = 0.029). Overall, breast cancer risk was highest (OR = 1.5) between 70 nmol/L and 80 nmol/L of serum 25(OH)D concentration. Then after serum 25(OH)D 80 nmol/L concentration, the breast cancer risk declined. In multivariate-adjusted logistic regression, the risk of having breast cancer was significantly higher in serum 25(OH)D 75–˂100 nmol/L category compared to the 25(OH)D < 30 nmol/L category [OR and 95% CI: 2.4 (1.4–4.0)]. In conclusion, serum vitamin D concentrations ≥ 100 nmol/L are associated with reduced risk of breast cancer in postmenopausal women. Controlled trials are required to verify if serum 25(OH)D ≥ 100 nmol/L offers protection against breast cancer in postmenopausal women.

Background: Post-menopausal women are at high risk for breast cancer. The association between serum 25-hydroxyvitamin D [25(OH)D] concentration and breast cancer in post-menopausal women is not well understood. Objectives: The aim of this study was to investigate the association between serum 25(OH)D and breast cancer using nationally representative sample surveys. Methodology: In this cross-sectional study, we used seven cycles of National Health and Nutrition Examination Surveys from 2001 through 2014. Participants were non-institutionalized post-menopausal women (n=8100). Logistic regression was performed to determine the association between serum 25(OH)D concentrations and breast cancer prevalence. A restricted cubic spline method was used to assess the non-linear association. Results: The prevalence of breast cancer was 3.3%, 4.0%, 4.6%, 6.4%, and 6.9% in the groups with serum 25(OH)D levels of <30, 30-<50, 50-<75, 75-<100, and ≥100 nmol/L, respectively. The risk of having breast cancer was significantly higher in the serum 25(OH)D 75-<100 nmol/L category compared to the 25(OH)D <30 nmol/L concentration [OR and 95% CI; 2.21 (1.23-3.98)]. Furthermore, a significant non-linear relationship between serum 25(OH)D concentrations (when used as a continuous variable) and breast cancer in all post-menopausal women (p for non-linear trend 0.032) was observed. Overall, the risk of breast cancer was highest (OR=1.5) between 70 nmol/L and 80 nmol/L of serum 25(OH)D concentration in all post-menopausal women. Conclusion: An adverse association was observed between serum 25(OH)D concentration and breast cancer in post-menopausal women. Further research is needed to elucidate the mechanism of vitamin D in cancer pathogenesis.