Researchers have concluded that there is no ‘highly convincing’ evidence that vitamin D supplementation improves outcomes after conducting an analysis of the evidence.
The two large meta-analyses published in the BMJ today cast doubt on Department of Health advice to offer vitamin D supplements to certain groups of people considered at risk of vitamin D deficiency.
However, researchers did say that benefits from vitamin D supplementation were ‘probable’ in some at-risk groups.
Experts said the findings suggest GPs should be cautious about prescribing vitamin D supplements widely in people without symptoms, until the risks as well as the benefits have been properly evaluated.
The DH currently recommends vitamin D supplements should be given to several at-risk groups including pregnant and breastfeeding women, infants and children under five years and older people over 65, as well as middle-aged people who get little sun exposure and those with darker skin.
However, one of the new papers found evidence from meta-analyses of observational and randomised data only consistently supported an association for one health outcome and vitamin D levels. This was birthweight, which was linked with maternal vitamin D levels in late pregnancy.
The authors said the evidence also suggested vitamin D supplementation ‘probably’ reduces the risk of dental caries in children and decreases parathyoid hormone levels in patients with chronic kidney disease, as well as increasing maternal vitamin D levels at term. But they said there was no evidence to support vitamin D only supplementation to increase bone mineral density or to prevent fractures or falls in older people.
The team concluded: ‘Despite a few hundred systematic reviews and meta-analyses, highly convincing evidence of a clear role of vitamin D does not exist for any outcome, but associations with a selection of outcomes are probable.’