Public interest has 'medicalised' vitamin D yet benefits remain uncertain

Persistent public interest in vitamin D, plus widespread testing of vitamin D status and prescribing by doctors, has led to a significant increase in people taking supplements despite limited evidence of any health benefits – according to new NIHR-funded research from Queen Mary University of London and published in BMJ Open.

A team of researchers set out to explore public knowledge, beliefs and attitudes to vitamin D by holding a focus group study of 58 adults in East London. The study found many respondents lacked knowledge about vitamin D, including dietary sources and government recommendations. Many had opposing views on the fortification of food products and many were also confused about the risks and benefits of sunshine in association with vitamin D.

In addition, excessive testing and supplementation via health professionals has contributed to a medicalised view of vitamin D. While potentially useful in some high-risk groups (vitamin D deficiency is common and is associated with a range of illnesses) scientists are still unsure about the clinical significance of deficiency and the impact of supplementation. Clinical trials to test the efficacy of vitamin D supplements have largely had inconsistent results and there is no official consensus on the benefits of supplementation.

The study revealed one East London hospital laboratory processed a 10-fold increase in vitamin D test requests – largely from GP practices – over a 5-year period from 2006 to 2010, reaching 44,500 per year. Prescribing of vitamin D preparations has risen dramatically, with eight in every 100 east London patients receiving vitamin D. In the London borough of Tower Hamlets, the number of patients prescribed vitamin D outstripped that for statins, aspirin, and proton pump inhibitors.

Professor Chris Griffiths, who led the study at Queen Mary University of London, comments: "Use of vitamin D as a Google search term increased fivefold over the last decade. It's gone from being a subject of scientific interest to a big public conversation – yet we lack a clear benchmark of the public's knowledge on vitamin D and this is vital to inform professional guidance and public health initiatives.

"Our findings highlight the need for accessible, reliable public information on vitamin D, and clear guidance on the risk and benefits of sun exposure. In particular, this information needs to differentiate between the advice for the general population and those at high risk of vitamin D deficiency."

"Doctors and the general public need to be aware of the limited evidence that vitamin D supplementation improves health, and we encourage doctors to consider this lack of evidence more carefully when testing and prescribing."

Professor Adrian Martineau, Co-Author and vitamin D expert at Queen Mary University of London, added: 'There is growing interest in the potential for food fortification to reduce the prevalence of profound vitamin D deficiency in the UK population, following the lead of countries like the USA and Finland. Our research suggests that, while some members of the general public are open to such an approach, others remain sceptical. We hope that our findings will help the Department of Health to design appropriate and acceptable fortification strategies if a decision is made to go down this road.'