Health risks and benefits from calcium and vitamin D supplementation: Women's Health Initiative clinical trial and cohort study.
Study Goal
The researchers aimed to determine whether calcium plus vitamin D supplementation reduces hip fractures, total fractures, and colorectal cancer in postmenopausal women, while also examining broader health benefits and risks.
Results Summary
Long-term calcium and vitamin D supplementation showed a potential reduction in hip fracture risk among women not taking personal supplements at baseline, with suggestive but inconclusive evidence for reduced breast and total invasive cancer risks. No significant effects were observed on cardiovascular disease, colorectal cancer, or total mortality.
Population
Postmenopausal women in the U.S.
Effective Dosage
1,000 mg elemental calcium carbonate plus 400 IU vitamin D(3) daily
Duration
Average of 7.0 years
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
1,000 mg elemental calcium carbonate plus 400 IU of vitamin D(3) daily | decrease | hip fracture | postmenopausal women in the U.S. | - | reduce | #1 |
1,000 mg elemental calcium carbonate plus 400 IU of vitamin D(3) daily | decrease | total fracture | postmenopausal women in the U.S. | - | reduce | #2 |
1,000 mg elemental calcium carbonate plus 400 IU of vitamin D(3) daily | decrease | colorectal cancer | postmenopausal women in the U.S. | - | reduce | #3 |
calcium and vitamin D supplementation | decrease | hip fracture | women not taking personal calcium or vitamin D supplements at baseline | 0.62 (95 % confidence interval (CI), 0.38-1.00) | hazard ratio for hip fracture occurrence | #4 |
calcium and vitamin D supplementation | decrease | hip fracture | women not taking personal calcium or vitamin D supplements at baseline | 0.65 (95 % CI, 0.44-0.98) | hazard ratio for hip fracture occurrence | #5 |
calcium plus vitamin D supplementation | no change | myocardial infarction | - | - | effects were not apparent on the risks | #6 |
calcium plus vitamin D supplementation | no change | coronary heart disease | - | - | effects were not apparent on the risks | #7 |
calcium plus vitamin D supplementation | no change | total heart disease | - | - | effects were not apparent on the risks | #8 |
calcium plus vitamin D supplementation | no change | stroke | - | - | effects were not apparent on the risks | #9 |
calcium plus vitamin D supplementation | no change | overall cardiovascular disease | - | - | effects were not apparent on the risks | #10 |
calcium plus vitamin D supplementation | no change | colorectal cancer | - | - | effects were not apparent on the risks | #11 |
calcium plus vitamin D supplementation | no change | total mortality | - | - | effects were not apparent on the risks | #12 |
calcium plus vitamin D supplementation | decrease | breast cancer risk | - | - | evidence for a reduction | #13 |
calcium plus vitamin D supplementation | decrease | total invasive cancer risk | - | - | evidence for a reduction | #14 |
calcium and vitamin D | decrease | risk of hip fracture | postmenopausal women | - | appears to confer a reduction that may be substantial | #15 |
calcium and vitamin D supplementation | increase | urinary tract stone formation | - | - | an elevation | #16 |
SUMMARY: The Women's Health Initiative (WHI) double-blind, placebo-controlled clinical trial randomly assigned 36,282 postmenopausal women in the U.S. to 1,000 mg elemental calcium carbonate plus 400 IU of vitamin D(3) daily or placebo, with average intervention period of 7.0 years. The trial was designed to test whether calcium plus vitamin D supplementation in a population in which the use of these supplements was widespread would reduce hip fracture, and secondarily, total fracture and colorectal cancer. INTRODUCTION: This study further examines the health benefits and risks of calcium and vitamin D supplementation using WHI data, with emphasis on fractures, cardiovascular disease, cancer, and total mortality. METHODS: WHI calcium and vitamin D randomized clinical trial (CT) data through the end of the intervention period were further analyzed with emphasis on treatment effects in relation to duration of supplementation, and these data were contrasted and combined with corresponding data from the WHI prospective observational study (OS). RESULTS: Among women not taking personal calcium or vitamin D supplements at baseline, the hazard ratio [HR] for hip fracture occurrence in the CT following 5 or more years of calcium and vitamin D supplementation versus placebo was 0.62 (95 % confidence interval (CI), 0.38-1.00). In combined analyses of CT and OS data, the corresponding HR was 0.65 (95 % CI, 0.44-0.98). Supplementation effects were not apparent on the risks of myocardial infarction, coronary heart disease, total heart disease, stroke, overall cardiovascular disease, colorectal cancer, or total mortality, while evidence for a reduction in breast cancer risk and total invasive cancer risk among calcium plus vitamin D users was only suggestive. CONCLUSION: Though based primarily on a subset analysis, long-term use of calcium and vitamin D appears to confer a reduction that may be substantial in the risk of hip fracture among postmenopausal women. Other health benefits and risks of supplementation at doses considered, including an elevation in urinary tract stone formation, appear to be modest and approximately balanced.