Sunlight is underrated. It has been vilified for decades as a cause of melanoma and other skin cancers. But sun avoidance is also a cause of low vitamin D 1, which may increase all-cause mortality. 2 The most likely answer is that sunlight in moderation is beneficial. Fifteen minutes of sun per day on exposed skin — without sunscreen — will increase vitamin D production in most people and help to maintain a healthy circadian rhythm. Also, I find that if I’ve been outside in daylight without glasses or contact lenses, I get tired earlier at night — your mileage may vary, of course.
- Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988-2004. Archives of Internal Medicine, 2009. ↩
- Vitamin D Supplementation and Total Mortality: A Meta-analysis of Randomized Controlled Trials. Archives of Internal Medicine, 2007. ↩