Vitamin D and Mortality -- Are They Linked?
Vitamin D, "the sunshine vitamin," is rarely out of the news nowadays, with reports of new studies contributing regularly to the ongoing debate about optimal levels of the hormone, indications for testing, and need for supplementation. Traditionally associated with skeletal disease including osteoporosis and fractures, low levels of serum 25-hydroxyvitamin D (25[OH]D), the metabolite usually measured as a mark of vitamin D status, more recently have been linked to a wide range of nonskeletal diseases, including some cancers and autoimmune, cardiometabolic, and neurologic diseases.
A number of studies also have reported an inverse association between 25(OH)D concentration and all-cause mortality. However, most of the evidence for (and against) this association has come from observational studies and has yet to be confirmed in clinical trials. Meta-analyses have almost all concluded that lower 25(OH)D levels are associated with a significantly increased mortality risk.[1,2,3,4,5,6,7]
To explore this association more, Medscape reached out to Dr. Cedric Garland, a well-known expert on vitamin D. Dr. Garland is a professor in the Division of Epidemiology, Department of Family and Preventive Medicine, and a Fellow of the American College of Epidemiology. He has a Doctor of Public Health degree from University of California San Diego and studied epidemiology at Johns Hopkins. His research has focused on vitamin D status in health and the association between vitamin D deficiency and increased risk for disease, including some common cancers (breast cancer, colon cancer, leukemia, and melanoma) and diabetes. He is active in seeking to reduce the risk for cancer and diabetes by improving vitamin D status among the US population.
To examine the relation between serum 25(OH)D and mortality, Dr. Garland and colleagues at the University of California San Diego and others in the United States pooled data from 32 studies published between 1966 and 2013. They found an overall relative risk of 1.8 (95% confidence interval [CI]: 1.7-1.8; P <.001) comparing the lowest (0-9 ng/mL) with the highest (>30 ng/mL) category of 25(OH)D for all-cause mortality. Serum 25(OH)D concentrations ≤30 ng/mL were associated with higher all-cause mortality than concentrations >30 ng/mL (P <.01).
The investigators noted that these findings confirmed observations from the Institute of Medicine (IOM) that 25(OH)D levels of <20 ng/mL are too low for safety, but they suggested a cut-off point of >30 ng/mL rather than >20 ng/mL for all-cause mortality reduction. This level "could be achieved in most individuals by intake of 1000 IU per day of vitamin D3," the investigators said, noting that this is described as a safe dose in almost all adults by both the IOM and Endocrine Society clinical guidelines on dietary intake of vitamin D.
Dr. Garland spoke with Linda Brookes, for Medscape, about research, both his own and others, examining the relationship between vitamin D status and mortality and the implications for clinical practice.
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Cite this: Vitamin D and Mortality Risk: Should Clinical Practice Change? - Medscape - Aug 13, 2014.