People with very low levels of vitamin D appear to be at higher risk of death from all causes (including cancer) according to a paper published in the BMJ.
The study from the German Cancer Research Centre paid particular attention the impact of vitamin D in people from different countries, sexes and ages.
Women are more prone to low vitamin D than men and different climates across the world also means that concentrations of vitamin D vary in different populations.
The elderly, who often have less sun exposure, often lack vitamin D.
Vitamin D is made by the body under the skin when it is exposed to sunlight. A deficiency can cause problems when there is not enough of the vitamin to properly absorb the required levels of calcium and phosphate.
Mild to moderate vitamin D deficiency can lead to bone pain and weakening of the bones – osteoporosis – which increases the risk of fractures.
The study found there was no clear trend of vitamin D by age, but women had lower average levels than men.
It concluded that people with the lowest levels of vitamin D had an association "with increased all-cause mortality, cardiovascular mortality, and cancer mortality (in subjects with a history of cancer)".
The researchers believe the possible impact of low vitamin D is of "high public health relevance" and should be given high priority.
The meta-analysis of studied from Europe and the US also says that vitamin D could play an important role in cancer prognosis.
Commenting on the study, Dr Carrie Ruxton an independent dietician from the Health Supplements Information Service (HSIS) notes: “Blood levels of 25-hydroxyvitamin D (25-OHD) were classified into fifths or quintiles within this meta-analysis. People in the lowest quintile of plasma 25OHD level had a 57% greater risk of death from all causes than those in the top quintile of plasma 25OHD. Considering risk of death from cardiovascular disease, the findings were of approximately the same magnitude, in other words a significantly higher risk of death from cardiovascular disease (CVD) among those with the lowest blood levels of 25-OHD. With respect to cancer this higher risk, in this case a 70% higher risk, was seen only among those people with a history of cancer.”
“These observational results concur with results of intervention studies. When systematically reviewing the evidence of efficacy of vitamin D supplementation high quality meta-analyses show a significant decrease in mortality of five to six per cent. A recent Cochrane review of intervention studies comparing placebo to supplementation of vitamin D with or without calcium showed that, overall, vitamin D3 significantly decreased mortality by six per cent.
“Significant numbers of people in the UK have low blood levels of 25-OH D. In the latest National Diet and Nutrition Survey (NDNS) results from years 1-4 combined, vitamin D deficiency (determined by low plasma 25-hydroxy vitamin D levels) was found in 23% of adults aged 19 to 64 years, 22% of children aged 11 to 18 years and 14% of children aged 4 to 10 years. This rose to 40% of adults aged 19 to 64 years and children aged 11 to 18 years during Winter months.”
In summary, Dr Ruxton notes: “It is clear that intakes of vitamin D in the UK are lower than recommended. The Scientific Advisory Committee on Nutrition (SACN) has stated that optimal intakes of vitamin D are unlikely to be met without vitamin D supplementation. SACN are in the process of reviewing their advice on Dietary Reference Values (DRVs) for Vitamin D with the intention of making recommendations for intake levels in the UK.”