Published June 2024 in The Atlantic
Article by Rowan Jacobsen
Article Excerpt
Australia is a country of abundant sunshine, but the skin of most Australians is better adapted to gloomy England than the beaches of Brisbane. The country’s predominantly white population has by far the world’s highest rate of skin cancer, and for years the public-health establishment has warned residents about the dangers of ultraviolet light. A 1980s ad campaign advised Australians to “Slip, Slop, Slap”—if you had to go out in the sun, slip on a shirt, slop on some sunscreen, and slap on a hat. The only safe amount of sun was none at all.
Then, in 2023, a consortium of Australian public-health groups did something surprising: It issued new advice that takes careful account, for the first time, of the sun’s positive contributions. The advice itself may not seem revolutionary—experts now say that people at the lowest risk of skin cancer should spend ample time outdoors—but the idea at its core marked a radical departure from decades of public-health messaging. “Completely avoiding sun exposure is not optimal for health,” read the groups’ position statement, which extensively cites a growing body of research. Yes, UV rays cause skin cancer, but for some, too much shade can be just as harmful as too much sun.
It’s long been known that sun exposure triggers vitamin D production in the skin, and that low levels of vitamin D are associated with increased rates of stroke, heart attack, diabetes, cancer, Alzheimer’s, depression, osteoporosis, and many other diseases. It was natural to assume that vitamin D was responsible for these outcomes. “Imagine a treatment that could build bones, strengthen the immune system and lower the risks of illnesses like diabetes, heart and kidney disease, high blood pressure and cancer,” The New York Times wrote in 2010. “Some research suggests that such a wonder treatment already exists. It’s vitamin D.” By 2020, more than one in six adults were on that wonder treatment in the form of daily supplements, which promise to deliver the sun’s benefits without its dangers.
But sunlight in a pill has turned out to be a spectacular failure. In a large clinical trial that began in 2011, some 26,000 older adults were randomly assigned to receive either daily vitamin D pills or placebos, and were then followed for an average of five years. The study’s main findings were published in The New England Journal of Medicine in 2018, and additional results were released in the same publication two years ago. An accompanying editorial, with the headline “A Decisive Verdict on Vitamin D Supplementation,” noted that no benefits whatsoever had been found for any of the health conditions that the study tracked. “Vitamin D supplementation did not prevent cancer or cardiovascular disease, prevent falls, improve cognitive function, reduce atrial fibrillation, change body composition, reduce migraine frequency, improve stroke outcomes, decrease age-related macular degeneration, or reduce knee pain,” the journal said. “People should stop taking vitamin D supplements to prevent major diseases or extend life.”
Australia’s new guidance is in part a recognition of this reality. It’s also the result of our improved understanding of the disparate mechanisms through which sunlight affects health. Some of them are intuitive: Bright morning light, filtered through the eyes, helps regulate our circadian rhythms, improving energy, mood, and sleep. But the systemic effects of UV light operate through entirely different pathways that have been less well understood by the public, and even many health professionals. In recent years, that science has received more attention, strengthening conviction in sunlight’s possibly irreplaceable benefits. In 2019, an international collection of researchers issued a call to arms with the headline “Insufficient Sun Exposure Has Become a Real Public Health Problem.”