Populations that lack exposure to sunlight during winter months should take vitamin D supplements to reduce their risk of cancer, warns a letter published in this week's British Medical Journal.
Professor Cedric Garland of the University of California challenges a previous editorial warning against the dangerous rays of the sun. He argues that staying out of the sun altogether could cause a severe deficiency of the vitamin, which has been linked in studies to protection against cancers of the colon, breast, prostate and others.
Sunlight is a major source of vitamin D and finding equivalent amounts in the diet is difficult for many north European populations.
Professor Garland writes: "People in the United Kingdom cannot synthesise vitamin D from November to the end of March, like residents of Boston. The half life of the storage form of vitamin D is about three weeks, so Britons become deficient by December."
He suggests that UK residents should spend 10-15 minutes a day in the sun without sunscreen and also take supplements of vitamin D3 - 400 IU per day for adults and children aged 1 year and older. Adults aged 71 and older should receive 600 IU (15 ug) daily, he says.
While the letter caused reaction from skin cancer experts, it does confirm growing concern among the medical community, which is seeing increasing cases of rickets. It is thought that current lifestyle factors, including fear of exposure to the sun, are causing a resurgence in the disease, almost eradicated in recent years.
A recent study published in the Lancet also cited the promotion of exclusive breastfeeding for long periods without vitamin D supplementation as a factor behind the growing incidence.