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"Our study shows that low vitamin D levels do result in higher mortality rates, but the best way of increasing vitamin D levels in the population remains unclear," says Børge Nordestgaard. (Credit: Bryan Robb/Flickr)

cancer

Is low vitamin D deadly?

A study of 96,000 Danes adds yet more evidence suggesting a vitamin D deficiency can raise the risk for cancer and death.

“We have conducted a major Danish study, in which we have examined the connection between genes associated with permanent low levels of vitamin D and mortality. We can see that genes associated with low vitamin D levels involve an increased mortality rate of 30 percent and, more specifically, a 40 percent higher risk of cancer-related deaths.

“An important factor in our study is that we have established a causal relationship,” says Shoaib Afzal, a physician at Copenhagen University Hospital.

In the scientific study, which is based on the Copenhagen City Heart Study and the Copenhagen General Population Study, vitamin D levels were measured using blood samples from both studies, and specific genetic defects were examined. All participants were followed for mortality from 1976 until today.

Sun, food, or supplements?

“In previous studies, a close statistical relationship has been established between low vitamin D levels and increased mortality rates. However, the fact that vitamin D deficiency can be a marker for unhealthy lifestyles and poor health in general may have distorted the results.

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“This led to our current study, which was based on an examination of the participants’ genes—genes which cannot be explained by unhealthy lifestyles,” says Børge Nordestgaard, a professor at the Faculty of Health and Medical Sciences at the University of Copenhagen and chief physician at Copenhagen University Hospital.

“Our study shows that low vitamin D levels do result in higher mortality rates, but the best way of increasing vitamin D levels in the population remains unclear,” says Nordestgaard.

“We still need to establish the amount of vitamin D to be added, as well as how and when it is most effective: Should we get vitamin D from the sun, through our diet, or as vitamin supplements? And should it be added in the fetal stage via the mother, during childhood, or when we have reached adulthood?”

When the sun shines on our skin, the skin produces vitamin D. Evidence suggests that sunshine has a positive effect on our health, but sunburns must be avoided as they increase the risk of skin cancer. A diet rich in vitamin D or the intake of vitamin D supplements can also cover our need to some extent.

The researchers define “a low level” of vitamin D as “a level that is 20 nmol/L lower than normal.”

Read the results in the British Medical Journal.

Source: University of Copenhagen

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