A new study has linked vitamin D deficiency with an increased risk of death, especially from cardiovascular disease, in the latest evidence of the important role the vitamin plays in human health.
Researchers, led by Harald Dobnig of the Medical University of Graz, Austria, measured the vitamin D levels in 3,258 patients, average age 62, who visited a medical center in Austria between 1997 and 2000, then followed their cases for 7.7 years.
Almost twice as many of the patients with vitamin D deficiency died during the course of the study, according to results published Monday in the Archives of Internal Medicine, a publication of the Journal of the American Medical Association (JAMA).
Of 737 patients died, 307 were from the group with the lowest blood levels of vitamin D, while 103 were from the group with the highest.
The link between Vitamin D deficiency and mortality due to cardiovascular causes was particularly striking. More than half of the deaths -- 463, of 62.8 percent -- were attributed to cardiovascular causes.
Scientists do not know how low levels of vitamin D contribute to cardiovascular problems or other causes of death.
But study after study has shown that vitamin D plays an key role in human immunity.
A Harvard University study of 18,225 published in early June in the Archives of Internal Medicine showed a link between the frequency of heart attacks and low blood levels of Vitamin D.
Earlier research had shown a link between vitamin D deficiency and diabetes, obesity and high blood pressure.
Vitamin D deficiency has also been associated with several types of cancer.
At least 50 percent of older individuals worldwide have insufficient vitamin D in their blood, and the situation is similar for younger people, according to the Archives of Internal Medicine.
Possible causes are a decline in outdoor activity, aging and atmospheric pollution.
The chief source for vitamin D is sun exposure, since the ultraviolet rays of the sun trigger vitamin D synthesis within the human body. Ten to fifteen minutes a day in the sun is sufficient.
Considered key to bone health, it is naturally present in very few foods, fish, beef liver and egg yolks among them. Eighty-five grammes of canned tuna has 200 international units (IU) of vitamin D.
The American Institute of Medicine recommends 200 IU of vitamin D a day for children and adults up to the age of 50. Adults older than 50 should take 400 to 600 IU per day.
Some doctors think that is not enough and recommend dietary supplements, but excessive vitamin D can be dangerous.