Low levels of vitamin D and high levels of parathyroid hormone are associated with increased mortality in African American and Caucasian older adults, according to a new study accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM). The study also indicates that the potential impact of remediating low vitamin D levels is greater in African Americans than Caucasians because vitamin D insufficiency is more common in African Americans.
For the past several years, there has been considerable interest in the role vitamin D plays in improving health and preventing disease. Low levels of vitamin D have been directly associated with various forms of cancer and cardiovascular disease. Most studies regarding the health effects of low vitamin D levels have been conducted on persons of European origin, but the current study examines the relationship between vitamin D and mortality in blacks and whites.
"We observed vitamin D insufficiency (defined as blood levels <20 ng/ml), in one third of our study participants. This was associated with nearly a 50 percent increase in the mortality rate in older adults," said Stephen B. Kritchevsky, PhD, Professor of Internal Medicine and Transitional Science at the Wake Forest School of Medicine, and lead researcher of this study. "Our findings suggest that low levels of vitamin D may be a substantial public health concern for our nation's older adults."
In this study, 2,638 Caucasians and African-Americans aged 70-79 years were asked to fast for 12-hours, after which a blood sample was collected to determine levels of vitamin D. Every six months study participants were contacted to ascertain their medical condition. This study determined the proportion of deaths among participants of with different vitamin D levels. In addition to many health factors, the time of year was also taken into account due to the seasonal effects on vitamin D. Researchers found that levels of vitamin D less than 30 ng/ml were associated with significantly increased all-cause mortality.
"We all know that good nutrition is important to overall health and our study adds to a growing body of literature that underscores the importance of vitamin D and indicates that poor vitamin D nutrition is wide-spread," said Kritchevsky. "The good news is it's easy to improve vitamin D status either through increased skin exposure to sunlight or through diet or supplements."
Other researchers participating in the study include: Janet A. Tooze, Rebecca H. Neiberg, Gary G. Schwartz, M. Kyla Shea and Denise K. Houston of Wake Forest School of Medicine, Winston-Salem, NC; Dorothy B. Hausman, and Mary Ann Johnson of the University of Georgia, Athens, GA; Douglas C. Bauer and Susan M. Rubin of the University of California, San Francisco; Jane A. Cauley of the University of Pittsburgh in PA; Peggy M. Cawthon of California Pacific Medical Center in San Francisco; Tamara B. Harris of the National Institute on Aging, Bethesda, MD; and Francis A. Tylavsky of the University of Tennessee Health Science Center, Memphis, TN.
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