Vitamin D supplements reduce the risk of cancer death
Supplements with extra vitamin D reduce the risk of dying from cancer. Chinese epidemiologist Yu Zhang, who is affiliated with Affiliated Hospital of Chengdu University, comes to this conclusion in a meta-study published in BMJ.
There is an awful lot of positive scientific research on vitamin D, but the majority of this research concerns vitamin D levels or the estimated dietary intake of vitamin D.
Some caution with this investigation is appropriate. If people with a lot of vitamin D in their blood are healthier, is it because of vitamin D? Or are people who are healthy more often outside, so that their body produces more vitamin D? Not every association is caused by direct causation.
For that reason, Zhang's meta-study looked only at trials in which researchers gave vitamin D supplements to one group of people, and a placebo to another. If such trials are properly performed, they come up with causal relationships.
In total, Zhang found 52 trials, in which a total of 75454 subjects had participated. The studies also looked at the most robust health variable imaginable: mortality risk.
Zhang found a tendency for vitamin D supplements to lower the risk of death, but that trend was not statistically significant. This trend became more prominent when Zhang left out the trials in which subjects were given vitamin D2 instead of vitamin D3, but the trend was still not statistically significant.
When Zhang split his data by cause of death, he did find a statistically significant difference between the placebo group and the supplementation group. Vitamin D supplements reduced the risk of cancer death by 16 percent.
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Cancer Prevention & Survival