The link between levels of vitamin D – which is generated by sunshine – and death from all causes is "remarkably consistent" across different countries, researchers say today.
Most of the body’s vitamin D is made in the skin when exposed to ultraviolet B radiation from the sun. In the body, levels of vitamin D are usually determined by measuring a compound called 25(OH)D.
Dr Ben Schottker of the German Cancer Research Centre, Heidelberg, Germany, and his team analysed eight studies from 16 European countries and the US looking at the link between measurements of the compound and death risk. In total, the studies involved 26,018 men and women aged 50 to 79 years.
This showed that vitamin levels varied strongly by season (higher in summer), by country (higher in US and northern Europe) and by sex (higher in men). But no clear link to age was seen. During the studies’ follow-up periods there were 6,695 deaths, of which 2,624 were from cardiovascular diseases and 2,227 from cancer.
Those in the bottom fifth for vitamin levels had a 57% higher risk of death from any cause than those in the top fifth.
The risk for death from diseases of the heart and circulation was similarly high, but for cancer, there was only a link to 25(OH)D levels for those with a history of cancer (70% raised risk).
Details are published in the British Medical Journal.
"Despite levels of 25(OH)D strongly varying with country, sex, and season, the association between 25(OH)D level and all-cause and cause-specific mortality was remarkably consistent," report the authors.
They add that results are due soon from a long-term randomised trial of vitamin D supplements. Following these results, we will know if "supplementation can be recommended in most individuals with low 25(OH)D levels".
Schottker, B. et al. Vitamin D and mortality: meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States. BMJ 18 June 2014; doi: 10.1136/bmj.g3656 [abstract]
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