Study links low vitamin D levels with premature death

In recent months, there has been much debate surrounding vitamin D. Some studies have suggested that a high level of the vitamin benefits our health, while others have reported that there is not enough evidence to make such a claim. Now, a new study from the University of California-San Diego School of Medicine suggests a link between vitamin D deficiency and early death.

Vitamin D is a fat-soluble vitamin that helps regulate the absorption of calcium and phosphorus in our bones, as well as aid cell communication and strengthen the immune system.

Researchers have long associated vitamin D deficiency with poor bone health. In fact, 3 years ago, the US Institute of Medicine (IOM) concluded that low vitamin D is hazardous because it significantly increases the risk of bone disease.

But the health problems associated with vitamin D deficiency do not stop there. Last year, Medical News Today reported on a study led by the University of Kentucky, which indicated that vitamin D deficiency may damage the brain. More recent research claimed that low levels of vitamin D in the first 26 weeks of pregnancy may increase the risk of preeclampsia.

For this latest study, published in the American Journal of Public Health, the UC-San Diego team wanted to see how vitamin D deficiency influenced mortality rates.

Subjects with lower vitamin D levels 'twice as likely to die prematurely'

The researchers conducted a systemic review of 32 studies that analyzed vitamin D, blood levels and mortality rates. The studies involved 566,583 participants from 14 counties - including the US - who were an average age of 55.

"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 IU per day," says study co-author Heather Hofflich.

Participants' 25-hydroxyvitamin D levels were assessed. This is the main form of vitamin D found in human blood.

Results of the study revealed that participants with lower levels of 25-hydroxyvitamin D in their blood were twice as likely to die prematurely, compared with those who had higher blood levels of 25-hydroxyvitamin D.

Furthermore, the team found that the 25-hydroxyvitamin D blood level associated with approximately half of participants who were at higher risk of early death was 30 ng/ml - a level that around two thirds of Americans are already below.

According to the National Institutes of Health, children and adults ages 1-70 should have 600 IU (international units) of vitamin D each day, while adults over this age should have 400 IU a day.

But according to researchers in the Department of Medicine at the UC-San Diego School of Medicine:

"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 IU per day."

However, they add that patients should have their 25-hydroxyvitamin D blood levels checked annually and consult their doctor before adjusting their vitamin D intake.

Not all researchers are so positive about increasing vitamin D intake. Earlier this year, researchers reported on two studies published in the BMJ, which suggested that there is "no clear evidence" that vitamin D benefits health.

Another study, published in The Lancet Diabetes & Endocrinology in January, also questioned the health benefits of vitamin D, after an assessment of 40 randomized controlled trials revealed that vitamin D supplements are unlikely to reduce the incidence of heart attack, heart disease, stroke, cancer and bone fractures.

Another researcher at the University of Auckland in New Zealand, commented:

"The main message is that if you are otherwise healthy and active, you are likely to receive enough sunshine to have adequate vitamin D levels and don't need to take vitamin D supplements."