Moderate exposure to the sun has many benefits. Perhaps the most important of all is synthesis of vitamin D, a hormone-like substance that helps boost immunity and protect bone. Nearly 75 per cent of the body's vitamin-D supply comes from exposure to the sun - and sunscreens can drastically lower the body's production of this essential nutrient.
People who don't get enough vitamin D may be more prone to develop certain cancers, such as of the prostate, breast and colon (Cancer Res, 1995; 55: 4014-22), a number of immune disorders such as type 1 (insulin-dependent) diabetes and multiple sclerosis (MS) (Toxicology, 2002; 181-182: 71-8; Lancet, 2001; 358: 1476-8) and bone disorders such as rickets and osteoporosis.
Many of us shun the sun these days because we are afraid of the skin damage that overexposure can cause. But sunburn, photoageing and skin cancer are not inevitable if you adopt certain common-sense measures while outdoors.
* Adjust your sun exposure to your skin type. The most sun-sensitive are those of Celtic extraction, often with red hair, who hardly tan and burn easily, usually after about 20 minutes of British midsummer sun. The least sensitive are those with brown-to-black Afro-Caribbean skin and hair, who can stay longer in the sun without burning.
* Stay out of the sun during peak hours - between 11 am and 2 pm. This is especially important if you have not been exposed to the sun for some time.
* Frequent short exposures are better than prolonged exposure. Trying to get a year's worth of sunshine in one week will certainly result in burning.
* Wear a hat - it should be big enough to cover the more sensitive skin of your face, head and neck.
* If you must use a suncream - for instance, if you need to be outdoors for prolonged periods of time - choose one that contains a physical sunblocker such as zinc or titanium oxide, which works by reflecting ultraviolet (UV) radiation. On current evidence, these are probably safer for your skin than chemical sunscreens, which absorb UV, thus keeping it nearer the skin. An SPF (sun protection factor) of 15 is a good choice.
* Look for natural ingredients in your suncream, such as plant oils, and antioxidant vitamins E and C. These can enhance the ability of skin cells to repair cellular and DNA damage caused by UV exposure (Mol Carcinogen, 1999; 24: 169-76).
* Clothing has an SPF, too. Most summer clothes provide an SPF of more than 10, so purchasing specially designed clothing (reputed to block UV rays) is not only expensive, it's unnecessary. An average weight T-shirt provides an SPF of 7 (J Cutan Med Surg, 1998; 3: 50-3).
* Watch your diet. People whose diets are high in omega-6 polyunsaturated fats (such as sunflower, safflower and other vegetable oils) are more prone to have sun-damaged skin. Once consumed, these oils work their way to the skin surface, where sunlight oxidises them, which rapidly creates free radicals - unstable molecules that damage the cells' DNA, leading to photoageing as well as skin cancer (Nutr Cancer, 1987; 9: 219-26).
* Supplement. If you are going to be out in the sun, consider upping your intake of vitamins C and E. In one study, 2 g of vitamin C and 1000 IU of vitamin E daily reduced the tendency to sunburn (J Am Acad Dermatol, 1998; 38: 45-8). Beta-carotene is a safe and effective treatment for those whose skin is overly sensitive to sunlight due to a genetic disorder (JAMA, 1974, 228: 1004-8). UV exposure depletes the body of this nutrient, and the evidence indicates that supplementing with 25 mg of mixed carotenoids plus 500 IU of natural vitamin E will provide extra sunburn protection (Am J Clin Nutr, 2000; 71: 795-8).