Whether everyone – at least, everyone living in sun-deprived England – should consider vitamin D supplements in winter is still not resolved, according to a debate in the BMJ.
Arguing the case against routine supplementation, genetic epidemiologist Professor Tim Spector, also from King’s College London, said the thresholds for deficiency, adequacy and toxicity of vitamin D were rubbery at best and clinical deficiency did not emerge until the level dropped below 10 nmol/L.
“Despite a few hundred systematic reviews and meta-analyses, a recent review found highly convincing evidence of a clear causal role of vitamin D does not exist for any of 137 outcomes,” he said.
“We have unfortunately created another pseudo-disease that is encouraged by vitamin companies, patient groups, food manufacturers, and charities.
“Healthy people should get vitamin D from small doses of sunshine every day plus dietary sources and trust that millenniums of evolution will have dealt with the fact that in northern climes our vitamin D level naturally drops in winter without us snapping our limbs.”
However, nutritionist Dr Louis Levy, from King’s College London, said getting enough vitamin D to protect musculoskeletal health requires eating the right types of food and getting short bursts of daily sunshine in summer.
“However, for many people this can be harder to achieve than it sounds, and some people will need to take supplements in autumn and winter,” he said.
An evidence review by the UK’s Scientific Advisory Committee on Nutrition concluded that musculoskeletal health is at risk when serum 25-dihydroxy vitamin D levels drop below 25 nmol/L.
“This concentration is not diagnostic of disease: it represents a population protective level,” Dr Levy said.
A vitamin D intake of at least 10 μg/day is needed to ensure that 97.5% of the population reach this target.
“Vitamin D is found in only a small number of foods, including oily fish, red meat, liver and egg yolk, so it’s not easy to get what you need from your diet alone,” he said.
About one in five people in the UK did not have blood levels above 25 nmol/L even in the summer.
“Public Health England advises that…during autumn and winter the only source is diet and so everyone should consider a daily supplement of 10 μg during these months,” he said.
Population groups at special risk include those who are mainly confined indoors, who should take a supplement all year, those who wear clothing that covers most of the skin, and people with darker skin.