August 11, 2008 — (BRONX, NY) — Vitamin D plays an essential role in cell growth, boosting the immune system, and strengthening bones. Now a study in the August 11/25 issue of Archives of Internal Medicine reports that individuals with low levels of vitamin D may have an increased risk of death from all causes. The research was carried out by a team of scientists from Albert Einstein College of Medicine of Yeshiva University and Johns Hopkins University School of Medicine co-led by Dr. Michal L. Melamed, assistant professor of medicine and of epidemiology and population health at Einstein, and Dr. Erin D. Michos, an instructor at Johns Hopkins and its Heart and Vascular Institute.
In conducting the study, Drs. Melamed, Michos and colleagues analyzed vitamin D levels in 13,331 individuals who participated between 1988 and 1994 in the Third National Health and Nutritional Examination Survey (NHANES III), conducted by the Centers for Disease Control and Prevention. An unhealthy deficiency of vitamin D is considered to be a blood level of 17.8 nanograms per millileter or lower, while the optimal blood level is suggested to be 30 nanograms per milliliter or higher. Approximately 41 percent of U.S. men and 53 percent of U.S. women have levels lower than 28 nanograms per milliliter.
The researchers divided participants into four groups (quartiles), based on their vitamin D levels. They found that 1,806 of the participants died as of December 31, 2000. Participants in the group with the lowest vitamin D level (less than 17.8 nanograms per milliliter) had a 26 percent increased rate of death from any cause compared with those in the group with the highest vitamin D levels. However, no significant associations were found when the researchers assessed vitamin D levels and risk of death from cardiovascular disease or cancer alone.
"We know that low vitamin D levels may increase the risk of death by affecting physiological processes such as blood pressure and the body's ability to respond to insulin," said Dr. Melamed. "Our findings further clarify that we should all make sure that we have enough vitamin D if we are concerned about our overall health. An earlier paper of ours, from a later national survey, showed an 80 percent increase in risk of peripheral artery disease from vitamin D deficits. Those findings, along with these new ones highlight a trend demonstrated in other studies linking shortfalls in vitamin D levels to increased rates of breast cancer and depression in the elderly."
Since vitamin D deficiencies are known to pose health risks, Dr. Melamed and colleagues suggest that vitamin D should be added to the chemicals measured by routine blood tests. "People with low vitamin D levels can be advised of the need to raise them, which is easily done using supplements, eating certain foods and fortified dairy products, or getting as little as 15 minutes of exposure to the sun's vitamin-D producing ultraviolet rays," she says.
The researchers acknowledge that further studies are needed to confirm these findings and establish the mechanisms by which low vitamin D levels undermine health. In addition, randomized clinical trials will be needed to determine whether vitamin D supplementation at higher doses could have any potential benefit in reducing future mortality risk in those with vitamin D deficiency.
Dr. Melamed and and co-author Dr. Michos were supported by grants from the National Institutes of Health. Dr. Michos is also supported by the P.J. Schafer Cardiovascular Research Fund. Co-author Dr. Post is supported in part by the Paul Beeson Physician Faculty Scholars in Aging Program. Dr. Michos has received consulting fees from Abbott Pharmaceuticals.
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