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According to a new study, vitamin D levels measured in the blood can indicate premature death risk. Researchers from the University of California, San Diego School of Medicine reviewed studies examining the effects of low vitamin D levels on people's health. The researchers found that people who had lower levels of vitamin D in their blood were two times more likely to die prematurely when compared to people who had higher levels of vitamin D.

"Three years ago, the Institute of Medicine (IOM) concluded that having a too-low blood level of vitamin D was hazardous," said Cedric Garland, DrPH, professor in the Department of Family and Preventive Medicine at UC San Diego and lead author of the study. "This study supports that conclusion, but goes one step further. The 20 nanograms per milliliter (ng/ml) blood level cutoff assumed from the IOM report was based solely on the association of low vitamin D with risk of bone disease. This new finding is based on the association of low vitamin D with risk of premature death from all causes, not just bone diseases. "

For this study, the researchers conducted a systematic review on 32 previously published studies that included data on 566,583 people from 14 countries. The average follow-up period was nine years and the participants had an average age of 55 when their blood was drawn. These studies provided information on patients' vitamin D levels, blood levels and human mortality rates. Researchers had focused on a particular variant of vitamin D known as 25-hydroxyvitamint D, which is mostly found in blood.

The researchers found that roughly one half of the death rats was tied to a vitamin D blood level of 30 ng/ml. Since two-thirds of the population in the United States have levels lower than 30 ng/ml, the team stressed the importance of maintaining one's vitamin D blood levels with one's primary care physician.

"This study should give the medical community and public substantial reassurance that vitamin D is safe when used in appropriate doses up to 4,000 International Units (IU) per day," said Heather Hofflich, DO, professor in the UC San Diego School of Medicine's Department of Medicine reported in the press release. "However, it's always wise to consult your physician when changing your intake of vitamin D and to have your blood level of 25-hydroxyvitamin D checked annually. Daily intakes above 4,000 IU per day may be appropriate for some patients under medical supervision."

The study was published in the American Journal of Public Health and funded by the UC San Diego Department of Family and Preventive Medicine.