Golden rays of protection

Sunlight is fast becoming the new tobacco, and the message from dermatologists is clear - do not venture out into the sun's harmful rays unless you cover up or plaster yourself in a high-factor sunscreen.

But after spending a glorious weekend in the garden, I can't help thinking this is both Draconian and unrealistic. A view supported by Professor Michael Holick, the maverick skin specialist from Boston who has been hounded out of his post after daring to suggest that spending a bit of time in the sun could actually be good for us.

Holick believes that 5-10 minutes of unprotected exposure to sunlight three times a week boosts vitamin D levels enough to offer significant protection against a number of diseases, including some forms of cancer. Deficiency of the vitamin has been linked to multiple sclerosis (MS), diabetes, depression, osteoporosis, schizophrenia and cancer of the breast, prostate and colon.

A typical British adult requires five microgrammes of vitamin D a day (10 mcg for those over 50, and 15 mcg for those over 70) and most of this is produced by the action of UVB rays (the portion of sunlight responsible for sunburn) on the skin.

Our poor weather means that UVB levels are too low during the winter months to trigger significant vitamin D production, but that changes dramatically as the power of the sun increases during the summer, when spending around 10 minutes outside with your face, arms and lower legs exposed should be enough to prevent deficiency.

Wearing a sunscreen with an SPF of eight or more is enough to shut down this production.

Vitamin D also occurs naturally in food. Oily fish and dairy products are good natural sources, and staple foods like margarine and breakfast cereals are fortified with the vitamin. Despite this, deficiency is very common in the UK, affecting as many as eight out of 10 people at some stage during their lives.

Holick isn't suggesting we become sun worshippers. He advocates less than half an hour of unprotected exposure a week and most of us are likely to exceed this level already during the summer. Do you always put sunscreen on before popping to the local shop, or taking the dog around the block? Probably not, and those minutes of unprotected exposure quickly add up.

There is no doubt that too much sun causes premature ageing and increases the risk of skin cancer, but Holick offers a welcome reminder that we shouldn't avoid it altogether.

Michael Holick's controversial new book, The UV Advantage, is published by Prima Lifestyles.