Vitamin D deficiency linked to an increasing number of ailments

Low levels of vitamin D were linked to increased risk of death from conditions such as cancer and cardiovascular disease, according to a study published Tuesday in the journal BMJ.

The report is one of several released in the past few months linking vitamin D deficiency to increased cognitive impairment and aggressive prostate cancer.

Vitamin D is made naturally by the body through exposure of the skin to sunlight. Sunlight is the main source, though people also obtain the nutrient through supplements and foods including salmon, tuna, and mackerel. There is no agreement on how much vitamin D a person should have, but the National Institutes of Health says generally, levels that fall below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are considered too high.

In a meta-analysis released Tuesday in the BMJ, researchers looked at records of 26,000 men and women between ages 50 and 70 from the U.S. and several countries in Europe. The association between low levels of vitamin D in the blood and all-cause and cause-specific mortality was remarkably consistent, the study found. Patients with the lowest levels of serum 25-hydroxyvitamin D in their blood were about 1.5 times more likely to die of all causes and from heart diseases, than those with the highest levels. Those who had a history of cancer were 1.7 times more likely to die from the disease if they had lower levels of the vitamin in their blood. The findings were consistent across countries, sexes, age groups and time of the year when blood tests were done.

Low concentrations of vitamin D might be a marker for poor health status, the authors conclude, saying that more research is needed.

Indeed, the BMJ study is one among many that seem to indicate more research might be in order.

A study published this month in the American Journal of Public Health found people with low blood levels of vitamin D are more likely to die prematurely than are those with normal levels.

Another, published in May in Clinical Cancer Research, found vitamin D deficiency was an indicator of aggressive prostate cancer and spread of the disease in white and black men who underwent biopsies.

Also, in April, researchers from Wake Forest Baptist Medical Center published findings in the Journal of the American Geriatrics Society that suggested an association between low vitamin D levels and cognitive decline over time.

A search through clinicaltrials.gov found nearly 30 other active research studies regarding the vitamin.

At the same time, investigators in another analysis published in the BMJ in April sifted through data of 107 systematic literature reviews, 74 meta-analyses of observational studies and 87 meta-analyses of randomized controlled trials, all focused on vitamin D supplements. They could not draw conclusions about the benefit of its use in that form, and suggest further studies with better designed trials could help lead to firmer conclusions about the potential.

Follow Sabriya Rice on Twitter: @MHSRice