Book Review: Our Conflicted Relationship With the Sun

“Don’t leave home without sunscreen!” “No tan is worth the risk!” “Protect the skin you’re in!” If you haven’t heard these sun protection slogans, you’ve certainly heard a litany of others. The current dermatological guidelines decree the sun’s rays as a harmful carcinogen, so if you must be outside, slather yourself in a protective layer of sunscreen, wear protective clothing and seek shade during midday.

But just how much sun exposure should you get? That’s exactly the question that science journalist Rowan Jacobsen investigates in his new book, “In Defense of Sunlight: The Surprising Science of Sun Exposure.” And the answer is just as complex as our relationship with our shimmering star.

Humans evolved under the sun, and until the Industrial Revolution, lived most of their lives outside. Recent research shows that once we retreated indoors, we may have actually lost a number of health benefits bestowed by sunshine, and not just the natural source of vitamin D that our bodies generate in its rays.

When the sun kisses our skin, the latter triggers the release or production of a series of other compounds vital to our health. One is nitric oxide, a tiny molecule that acts as a natural vasodilator that relaxes blood vessels, bringing down blood pressure. It’s “also used by the brain to transmit signals, and by the immune system to kill pathogens,” Jacobsen writes.

Some compounds set off chain reactions in our bodies. “When our skin cells are exposed to sunlight, they produce a large molecule called proopiomelanocortin,” Jacobsen writes. Abbreviated as POMC, it’s a precursor to three essential chemicals. One of them prompts the production of melanin, Jacobsen writes, the dark pigment that helps protect the skin from burning, and which is also “a powerful antioxidant that excels at mopping up the damage caused by the sun’s rays.” The second compound raises the level of cortisol, the stress hormone that has a bad reputation, but only if your body produces it continuously and for a long time, Jacobsen clarifies.

The third POMC-derived compound is “an endorphin that heads for the brain and suffuses it with natural opioids, triggering a blissful state similar to what we get from morphine or opium,” Jacobsen notes. Plus, our skin contains a molecule called urocanic acid. Jacobsen highlights a 2018 mouse study that found that when activated by sunlight, the molecule enters the bloodstream and travels to the brain, where it becomes glutamate, a neurotransmitter that increases brain activity, and improves cognition and mood. An observational study in humans a few years later, he writes, “found that those who had been exposed to more sunlight in the preceding few years had significantly better cognitive function than those who lived in darker region.”

All that raises a question: How did science miss these important benefits? The answer may lie in our inability to do things in moderation — and Jacobsen walks us through several centuries of history to explain. Ancient civilizations used sunlight to treat skin diseases. Pliny the Elder recommended that “the most powerful, however, of all remedies, and one which is always at a person’s own command, is the sun.” In 19th century Europe, plagued by rickets, a medical missionary posited that sunbathing could be an effective cure.

Physician Niels Ryberg Finsen built a ultraviolet light-producing lamp to treat a type of tuberculosis, which gave rise to the concept of heliotherapy. In the early 20th century, Los Angeles-based naturopath Philip Lovell promoted the benefits of homes with flat roofs so that their dwellers could sunbathe. In 1926, an article in The Lancet called sunbathing “one of Nature’s greatest aids to maintaining and acquiring proper health.”

Heliotherapy became trendy. “A golden tan is the index of chic!” Jacobsen quotes Coco Chanel. The manufacturers of the UV lamps, Jacobsen notes, listened and quickly flooded the market with UV machines that people could buy. “Who needs the beach when modern technology allows you to get UV year-round in the comfort of your own home?” he writes. The lamps became super popular and received “the blessing of American Medical Association,” Jacobsen notes. One maker “urged parents to give children ultra-violet radiation in their playrooms.”

But as scientists learned more about skin cancer, messages changed. In the 1940s, magazines started warning zealous sunbathers about links between the sun and skin cancer, but suntanning remained popular. By the mid-1980s dermatologists sounded an alarm because skin cancer diagnoses went from 300,000 per year in the 1970s to 500,000 in 1985, Jacobsen writes. Part of it was that we learned to diagnose skin cancer better, Jacobsen points out, but the numbers were concerning nonetheless.

Enter the sunblock. In 1940s, the U.S. military developed a physical sunblock to prevent soldiers from being burned by the South Pacific sun during World War II, but the tanning industry quickly turned it into “a shield against death” for your average consumer. In the late 1970s, when the the Food and Drug Administration began regulating the sunscreen market, business was booming.

“When it released its initial guidelines,” Jacobsen writes, “the FDA assumed there would never be a need for an SPF [sun protection factor] higher than 15.” Indeed, according to the book, in 1987, the director of the agency’s cosmetics division wrote, “[T]here’s not enough ultraviolet light on Earth to warrant an SPF” higher than that. The public health campaigns to slather ourselves with sunblock with increasingly growing SPF levels have been on fire ever since.

Jacobsen doesn’t suggest we ditch the sunscreen. He doesn’t play down the dangers of skin cancer, either, but he cites a profound statistic. “Globally, skin cancer doesn’t even make the list of the forty deadliest killers. It’s responsible for about 120,000 deaths per year, which pales in comparison to the 20 million lives lost each year to cardiovascular disease,” or the millions lost to other types of cancer.

Nearly 99% of skin cancer cases are basal cell carcinomas and squamous cell carcinomas, which usually occur in places exposed to the sun — but they are highly treatable. The deadliest one, melanoma, is rare. Unlike other types of skin cancer, melanoma, Jacobsen writes, “ isn’t closely associated with lifetime sun exposure,” but rather “with a history of sunburns, especially during childhood.”

Meanwhile, most studies aimed at showing that sunscreen reduces skin cancer have not found that to be the case. In fact, Jacobsen notes, studies in the 1970s found a higher risk of cancer among sunscreen users. But later research found almost no difference, which “points to problems with those earlier sunscreens that were fixed in later formulations,” Jacobsen writes. He also cites a study that suggests insufficient sun exposure may have contributed to an estimated 820,000 deaths per year in Europe and the United States. Another study of more than 10,000 people in the U.K. and the Netherlands, found that exposure to bright sunlight was associated with lower insulin resistance and lower triglyceride levels.

Perhaps it’s time to reevaluate our relationship with the sun once again.

Fluctuating between serious, sarcastic and at times self-deprecating, Jacobsen upends everything we thought we knew about the science of our star and its powerful rays. Drawing on decades-long and recent research supplemented by interviews with scientists who challenge the existing scary sunscreen rhetoric, Jacobsen shows how easily solid science can be swayed by zealous marketing efforts in either direction. He does acknowledge that these new — or perhaps old and forgotten — views of the sun remain vehemently contested, but he hopes that finding a balance is possible.

The book also ushers in a newfound appreciation for our skin. Generally, we view our skin as a tough outer membrane that protects us from pathogens and environmental toxins. Jacobsen’s narrative makes us see it as “the organ that set the tone for the functioning of the entire body.”

Another uncanny realization is that we, humans, aren’t that different from plants, after all. We don’t photosynthesize, but, akin to plant cells, ours need the photons’ energy to derive and forge crucial life chemicals and reactions.

Woven throughout the book is a persistent call to look beyond trends and fearmongering tactics, for both consumers and public health authorities. People, when it comes to the sun, use common sense, Jacobsen pleads. Use moderation.

Reminiscent of Michael Pollan’s book “In Defense of Food,” which gave readers seven words of advice, “Eat food. Not too much. Mostly plants,” Jacobsen shares a pithy bit of his own shiny wisdom: “Get sun. Not too much. Go outside.”

This article was originally published on Undark. Read the original article.