Taking vitamin D with calcium supplements reduces fracture risk, especially for institutionalized seniors, but whether the sunshine vitamin prevents cancer is uncertain, according to a systematic review of the medical research published earlier this week in Annals of Internal Medicine.
Investigators at Tufts Medical Center in Boston and elsewhere analyzed 19 randomized controlled trials (16 for fracture risk and 3 for cancer outcomes) and 28 observational cancer studies.
The research on fracture risk involved mostly postmenopausal women around age 65. Analysis of the research findings indicate that taking vitamin D in combination with calcium supplements reduces fracture risk in older adults, but the preventive effects were smaller in community-dwelling seniors or postmenopausal women than in institutionalized older adults. Moreover, the analysis still does not make clear what the optimum dosing regimen might be.
The evidence on the benefits and harms of vitamin D supplementation for cancer prevention is inconclusive, the researchers reported. Limited data from randomized clinical trials suggested that high-doses of vitamin D supplements can reduce the risk for cancer, but data from observational studies suggested that higher blood concentrations (known as 25-hydroxyvitamin D) might be associated with increased risk. And one clinical trial showed adverse outcomes associated with supplementation, including increased risk for renal and urinary tract stones.
A separate review of the research on vitamin D and cardiovascular disease in the same issue of Annals of Internal Medicine found no clear evidence that vitamin D supplementation helps prevent cardiovascular disease. Researchers from the Royal College of Surgeons in Ireland, and Beaumont Hospital in Dublin, reported that vitamin D deficiency has been linked with hypertension, heart attack and stroke, as well as other cardiovascular-related diseases. But few randomized, controlled trials have evaluated the effect of vitamin D replacement on cardiovascular outcomes, and the results have been inconclusive or contradictory. Some large studies are currently underway.
Bottom line: The Tufts findings on fractures and cancer will help inform recommendations on taking vitamin D with or without calcium supplements expected soon from the U.S. Preventive Services Task Force, an independent group that develops recommendations on preventive health care. Meanwhile, it?s best to consult a physician before deciding whether to take vitamin D supplements since they might reduce the effectiveness of some medications.
Sources
Vitamin D With or Without Calcium Supplementation for Prevention of Cancer and Fractures: An Updated Meta-analysis for the U.S. Preventive Services Task Force [Annals of Internal Medicine]
New Insights About Vitamin D and Cardiovascular Disease [Annals of Internal Medicine] http://www.annals.org/
Read more about vitamin D.
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