BOSTON—Combined vitamin D and calcium supplementation can reduce fracture risk, according to a recent meta-analysis from Tufts Medical Center; however the researchers reported evidence hasn't determined vitamin D's role in cancer prevention (Ann Intern Med. 2011 Dec 20;155(12):827-38).
The meta-analysis was prepared for the U.S. Preventive Services Task Force, which conducts scientific evidence reviews of preventive health care and develops recommendations for primary care clinicians and health systems.
Researchers examined English-language studies identified from MEDLINE and the Cochrane Central Register of Controlled Trials through July 2011. These studies included randomized, controlled trials (RCTs), prospective cohort studies and nested case-control studies reporting incidence of or death from cancer and fracture outcomes. Most trial participants were postmenopausal women older than 65 years.
A highlight of the research findings:
- Limited data from RCTs suggested high-dose (1,000 IU/d) vitamin D supplementation can reduce the risk for total cancer, and data from observational studies suggested higher blood 25-hydroxyvitamin D (25-[OH]D) concentrations might be associated with increased risk for cancer.
- Mixed-effects dose-response meta-analyses showed that each 10-nmol/L increase in blood 25-(OH)D concentration was associated with a 6-percent reduced risk for colorectal cancer, but no statistically significant dose-response relationships for prostate and breast cancer.
- Random-effects model meta-analysis showed combined vitamin D and calcium supplementation reduced fracture risk in older adults, but the effects differed according to study setting: institution (relative risk, 0.71) versus community-dwelling (relative risk, 0.89).
- One RCT showed adverse outcomes associated with vitamin D supplementation, including increased risk for renal and urinary tract stones.
For more information on vitamin D and its health benefits, read INSIDER's article "Understanding Vitamin D."
