Vermont-based science writer Rowan Jacobsen challenges prevailing views on sun exposure in his new book, *In Defense of Sunlight: The Surprising Science of Sun Exposure* (Scribner), arguing that the benefits of sunlight may outweigh its risks. Drawing on a range of scientific studies, Jacobsen contends that moderate sun exposure contributes to longer, healthier lives and has significant physiological and psychological advantages.

Jacobsen's perspective shifted after reviewing a 2018 study published in *The Journal of Cell Science* by Chinese neurology researchers, which found that individuals with regular sun exposure experienced better overall health and longevity, even among those with conditions such as diabetes or heart disease. This research runs counter to conventional warnings that ultraviolet (UV) rays are primarily harmful and the main cause of skin cancer.

Further supporting his argument, Jacobsen references a 2014 Harvard Medical School study highlighting the positive effects of sunlight on mood and alertness. According to this research, exposure to the sun triggers the production of proopiomelanocortin (POMC) in skin cells, which splits into three compounds: one stimulates melanin production to protect against sunburn, another releases cortisol, promoting alertness and energy expenditure, and a third generates natural opioids that induce a sensation akin to a “state of bliss.”

Jacobsen recommends that individuals seek moderate daily sun exposure, adjusting for skin tone and geographic location. He notes that people with darker skin and those living in areas or seasons with less sunlight may require more time in the sun to experience its benefits.

Despite these assertions, public health messaging and the sunscreen industry emphasize sun avoidance to prevent skin damage and cancer. Jacobsen examines this tension, noting that the global sunscreen market—valued at approximately $15 billion—is largely driven by this protective stance. He cites a meta-analysis published in the *European Journal of Dermatology*, which reviewed 29 studies dating back to the 1970s and found a higher risk of skin cancer among sunscreen users, a complex result that fuels ongoing debate about sunscreen’s role in cancer prevention.

The commercial promotion of sunscreens gained momentum after the U.S. Food and Drug Administration (FDA) approved claims that these products reduce skin cancer risk in 1979, leading to widespread adoption of the Sun Protection Factor (SPF) system. However, Jacobsen raises concerns about the safety of sunscreen ingredients, highlighting studies from the Centers for Disease Control and Prevention (CDC) that found widespread contamination with chemicals like oxybenzone, which penetrates the skin, as well as the presence of phthalates and per- and polyfluoroalkyl substances (PFAS). These chemicals have been linked in other research to neurological, reproductive, and metabolic issues.

While not advocating for abandoning sunscreen entirely, Jacobsen advises more measured use, recommending applying sunscreen only when necessary and avoiding products with SPF higher than 30. His central message encourages a balanced approach: individuals should seek regular, moderate sun exposure to harness its health benefits, while using precautions to prevent overexposure and sunburn. “Get sun. Not too much. Go outside,” he summarizes, urging a reconsideration of the often one-sided narrative about the risks of sunlight.