Sunshine can help with some serious health problems, argues a new book

Book In Defense of Sunlight Rowan Jacobsen, Scribner (UK, US) About a hundred years ago, doctors actively encouraged sunbathing. Soldiers’ wounds, first world war surgeons had noticed, healed a lot faster when exposed to solar rays; people with arthritis felt their pain retreating, while those with bronchitis and lung infections found their coughs subsiding. Blood pressure in hypertensive patients dropped. The Lancet went so far as to declare it “one of nature’s greatest aids to maintaining and acquiring proper health”, and even called for more spaces to strip off in public. Advertisement “On first consideration, the idea of a community of people deliberately practising nudity, especially with municipal encouragement, strikes the average person as somewhat ridiculous,” reads one article from 1932. “But the discovery that the rays of the sun on the skin exert a beneficent effect on health has done something to undermine these prejudices… as long as they are done for the sake of health and… the sexes are segregated.” Today, we’re far more cautious. We are told to cover up and apply generous volumes of sunscreen to protect us from the harmful UV rays, even in the winter. But has this advice gone too far? That’s the argument of a fascinating new book, In Defense of Sunlight: The surprising science of sun exposure by journalist Rowan Jacobsen. He says he was inspired by the finding that sun exposure can trigger mood-boosting endorphins. “Like most people, I’d had it drilled into me since childhood that the sun was… the primary cause of skin cancer, and that the only acceptable amount of its rays that should be allowed to touch my unprotected skin was zero,” he writes. “But if we’re wired to seek out sunlight, there must be a reason.” Studies found that exposure to UV light releases nitric oxide in our skin, which reduces blood pressure Despite this slightly shaky premise (the brain’s pleasure system can prime us to seek out much that is unhealthy for us, including drugs, alcohol and sugar) Jacobsen builds a thoroughly convincing argument, as he documents the many surprising ways that moderate sun exposure can revitalise our bodies. The most famous benefits of sunlight once appeared to revolve around its role in the body’s production of vitamin D. Correlational studies suggested that high levels of the chemical seem to reduce the risk of many health problems, including obesity, diabetes, osteoporosis, heart attack, stroke, depression, respiratory infections and colorectal cancer. Yet Jacobsen notes that dietary supplements of the vitamin have largely failed to make an impact on any of these problems, except when someone has a severe deficiency. This leaves the intriguing possibility that measurements of people’s natural vitamin D levels were simply acting as a proxy of their overall sun exposure, which had been protecting the body through multiple other mechanisms. One likely pathway is nitric oxide, a chemical that causes our blood vessels to dilate. Scientists have recently started to conclude that nitric oxide deficiency is a major driver of hypertension, and – quite remarkably – a series of studies has found that exposure to UV light releases this tiny chemical in our skin, which then reduces blood pressure. The finding, Jacobsen suggests, may offer one more reason why people in Mediterranean countries tend to have such good health. The leafy veg of the region’s famous diet, he points out, contain lots of nitrates, but plentiful sunlight in those areas helps people’s bodies to convert this into nitric oxide, relaxing their cardiovascular system. Just adopting a Mediterranean diet has been shown to lower blood pressure, but not as much as also increasing sun exposure, writes Jacobsen: “It’s the combination of the two that does the trick and should be the foundation of a true Mediterranean diet.” Elsewhere, he points to evidence that moderate exposure to sunlight releases chemicals in the skin that help rein in an overactive immune system, which may explain why it appears to soothe conditions like multiple sclerosis – independently of vitamin D production– and type 1 diabetes. There is even evidence that the infrared wavelengths in sunlight, which can penetrate deep into our bodies, can stimulate our mitochondria, improving our metabolism. The dark cloud hanging over all this is, of course, the heightened risk of skin cancer that comes with sun exposure. Here, Jacobsen points out that most skin cancers are basal cell and squamous cell carcinomas, which don’t often spread to other parts of the body and are typically treatable with surgery. Melanoma is more dangerous, but it is relatively rare and still has a very high survival rate compared with other cancers. “Yes, sunlight is the major alterable risk factor for skin cancer, but deaths from heart disease are a hundred times higher than deaths from skin cancer,” Jacobsen writes. “And I think we need to find the risk-benefit ratio.” To support this, he points to an influential study of 30,000 Swedish women, which found that sun exposure was associated with a far lower risk of mortality: over a 20-year period, “sun avoiders” were about twice as likely to die as sun lovers. Clearly, we shouldn’t take this new-found appreciation of “heliotherapy” to extremes; The Lancet is unlikely to resurrect its campaign for nude sunbathing anytime soon. The balance of risks will depend on a huge number of factors, including skin tone, the season and the latitude, which makes it very hard to make general recommendations for optimum levels of sun exposure. In the end, Jacobsen’s advice is quite close to that of health services in the UK. Make the most of the mornings and evenings when the UV component is lower, he suggests, but cover up and find shade during the hottest times of day. He is a little ambivalent on the daily use of sunscreen outside of the riskiest periods, but agrees it is advisable whenever there is the possibility of burning. Even short periods of exposure, he says, may be enough to glean the benefits. For all the cutting-edge research this thought-provoking book describes, its message is remarkably simple. “Get sun. Not too much. Go outside.” It’s time we all saw the light. Three more great books on the sun’s role in our lives Life Time: The new science of the body clock, and how it can revolutionize your sleep and health by Russell Foster Many of us extend our days far into the night. Russell Foster’s guide to human circadian rhythms shows why this is a poor idea. Using his research, he urges us to harness them to enhance sleep, mood and mental focus. The Remarkable Life of the Skin: An intimate journey across our surface by Monty Lyman The skin is our largest, fastest growing and least understood organ. It is also, of course, the principal recipient of the sun’s rays. Doctor and research fellow Monty Lyman explores the organ’s major role in our health. Chasing the Sun: The new science of sunlight and how it shapes our bodies and minds by Linda Geddes Former New Scientist staffer Linda Geddes offers an in-depth exploration of the sun’s role in our lives across history and cultures – and exactly what we lose when we end up spending so much of our time indoors. David Robson is a science writer specialising in the human brain, body and behaviour. His latest book is The Laws of Connection: 13 social strategies that will transform your life When you make a purchase via the links on this page, we receive a commission.