Association of supplemental calcium and dairy milk intake with all-cause and cause-specific mortality in the UK Biobank: a prospective cohort study

Excessive Ca intakes have been proposed to associate with vascular calcification and a higher risk of prostate cancer. We investigated the associations of supplemental and dietary Ca intake with mortality using data from 497 828 UK Biobank participants. The average follow-up was 4 center dot 2 years and 14 255 participants died, 8297 from cancer, 2959 from CVD and 572 from respiratory disease. The use of Ca supplements and milk consumption were associated with differences in mortality in younger (<= 65 years) but not in older participants (>65 years, P-interaction <= 0 center dot 04 for all comparisons). Among participants <65 years, there was an inverse association between Ca supplementation (OR 0 center dot 91, 95 % CI 0 center dot 83, 0 center dot 99) and milk consumption (OR 0 center dot 93, 95 % CI 0 center dot 86, 1 center dot 00) with respect to all-cause mortality. In the same age group, milk drinkers had lower odds of cancer mortality (OR 0 center dot 89, 95 % CI 0 center dot 80, 0 center dot 98) but Ca supplement use was associated with increased odds of respiratory mortality (OR 1 center dot 69, 95 % CI 1 center dot 16, 2 center dot 74). All associations in participants aged >= 65 years were null after full adjustment. In sensitivity analyses stratified by hormone replacement therapy, Ca supplement use was associated with decreased odds of cancer mortality in users but increased risk in other women (OR 0 center dot 81, 95 % CI 0 center dot 69, 0 center dot 94 v. OR 1 center dot 17, 95 % CI 1 center dot 01, 1 center dot 35, respectively). To conclude, we saw little evidence for harm with dietary or supplemental Ca. Further studies are required to confirm the proposed interaction with hormone replacement therapy and to exclude reverse causation as a determinant in the association between Ca supplements and increased risk of respiratory diseases.