Book
In Defense of Sunlight
Rowan Jacobsen, Scribner (, )
About a hundred years ago, doctors actively encouraged sunbathing. Soldiers鈥� 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.
went so far as to declare it 鈥渙ne of nature鈥檚 greatest aids to maintaining and acquiring proper health鈥�, and even called for more spaces to strip off in public.
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鈥淥n first consideration, the idea of a community of people deliberately practising nudity, especially with municipal encouragement, strikes the average person as somewhat ridiculous,鈥� reads one article from 1932. 鈥淏ut the discovery that the rays of the sun on the skin exert a beneficent effect on health has done something to undermine these prejudices鈥� as long as they are done for the sake of health and鈥� the sexes are segregated.鈥�
Today, we鈥檙e 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鈥檚 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. 鈥淟ike most people, I鈥檇 had it drilled into me since childhood that the sun was鈥� 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,鈥� he writes. 鈥淏ut if we鈥檙e wired to seek out sunlight, there must be a reason.鈥�
Studies found that exposure to UV light releases nitric oxide in our skin, which reduces blood pressure
Despite this slightly shaky premise (the brain鈥檚 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鈥檚 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鈥檚 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, . Scientists have recently started to conclude that deficiency is a major driver of hypertension, and 鈥� quite remarkably 鈥� a series of studies has found that 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鈥檚 famous diet, he points out, contain lots of nitrates, but plentiful sunlight in those areas helps people鈥檚 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: 鈥淚t鈥檚 the combination of the two that does the trick and should be the foundation of a true Mediterranean diet.鈥�
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 like multiple sclerosis 鈥� 鈥� and type 1 diabetes. There is even evidence that the infrared wavelengths in sunlight, which can penetrate deep into our bodies, can , 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鈥檛 often spread to other parts of the body and are typically treatable with surgery. Melanoma is more dangerous, but it is relatively rare and .
鈥淵es, 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,鈥� Jacobsen writes. 鈥淎nd I think we need to find the risk-benefit ratio.鈥� To support this, he points to an , which found that sun exposure was associated with a far lower risk of mortality: over a 20-year period, 鈥渟un avoiders鈥� were about twice as likely to die as sun lovers.
Clearly, we shouldn鈥檛 take this new-found appreciation of 鈥渉eliotherapy鈥� 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鈥檚 advice is 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. 鈥淕et sun. Not too much. Go outside.鈥� It鈥檚 time we all saw the light.
Three more great books on the sun鈥檚 role in our lives
by Russell Foster
Many of us extend our days far into the night. Russell Foster鈥檚 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.
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鈥檚 rays. Doctor and research fellow Monty Lyman explores the organ鈥檚 major role in our health.
by Linda Geddes
Former New Scientist staffer Linda Geddes offers an in-depth exploration of the sun鈥檚 role in our lives across history and cultures 鈥� 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
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