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A new study suggests that lower levels of vitamin D and high levels of parathyroid hormone could be tied to increased mortality among older African-American and Caucasian.

Also, according to the study, the potential impact of correcting vitamin D deficiency is harder for African-Americans than Caucasians since former group have a more severe insufficiency of vitamin D.

Previous studies have associated low levels of vitamin D with various forms of cancer and cardiovascular diseases. However, most of these studies have been conducted on people of European origin. 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."

For the current study, the researchers asked the participants (2,638 Caucasians and African-Americans aged between 70 and 79 years) to fast for 12-hours. After the fasting, a blood sample of the participants was collected to determine the levels of vitamin D.

The participants were asked to ascertain their medical condition, after every six months, so that the researchers could determine the proportion of deaths among participants of with different vitamin D levels.

Apart from the health factors, the researchers also considered the time of year due to the seasonal effects on vitamin D.

The findings revealed that vitamin D levels, less than 30 ng/ml was significantly associated with 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."

The study has been accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology and Metabolism (JCEM).