Recommended reading: In Defense of Sunlight

Light exposure is good for you. All the different frequencies are good for you. This has led many people to try to tweeze them apart: tanning beds, red-light panels and masks, therapy lights, etc. It turns out, sunlight is best consumed whole, just like food.

I should mention that by inclination, I’m rather vulnerable to getting this wrong. I wrote at some length about how, because of the sort of person I am, I simply like the idea of figuring out all the nutrients I need, and then trying to construct a diet that provides all those things. Similarly, I like the idea of coming up with a perfect workout plan, and then getting all the movement that I need by hitting all the right exercises. But, if you follow that link, you’ll see that I eventually realized the whole notion was just wrong-headed.

There is no need—in fact, no value—in tweezing apart the nutrients in food. Just eat a varied, whole-food diet and your body will get it right. The same with movement. Just engage in a wide range of diverse movement, and your body will become highly capable of moving in all those ways, (and if your “movement diet” is adequately diverse, your body will become fairly capable of all sorts of movements you don’t even practice).

The same is true of sunlight. That’s the main message of In Defense of Sunlight: The Surprising Science of Sun Exposure by Rowan Jacobsen.

The book is consciously modeled on Michael Pollan’s In Defence of Food, which systematically destroyed the notion that you could build up a diet that optimized all the nutrients. And it’s message is very similar. Sunlight is best consumed whole, just like food.

All of the different frequencies are good for you:

UV (to make vitamin D, and to release nitric oxide from the skin into the blood),

blue (to tell your brain it is daytime, and to tell your subcutaneous fat cells to release fat and signal your brown fat to burn it for energy),

green and yellow (to calm you down—I have written before about my theory of dappled shade, and for vision—you see shades of yellow better than shades of white, which is why yellow glasses are good for driving, shooting, and the like),

red light and infrared light (to boost energy production in your mitochondria and promote wound healing).

“But what about skin cancer!?!?” I can hear you asking from here.

The book is well worth reading, because just the information on skin cancer is worth the price of the book (and it takes half the book to adequately deal with the subject). Because there’s so much of it, it’s not really practical to try to summarize it here, so I’ll just mention that “Don’t get sunburned” is much better advice than “Put on sunbock,” or even “Stay out of the sun.”

I figured this out years ago. I’ll use sunblock if I’m going to be out in the sun so long that I might get sunburned—I needed it for a snorkling trip to Buck Island, for example. Otherwise, I use a combination of changing my clothes, taking advantage of shade, and limiting my time out in the midday sun. But I don’t minimize my time in the sun. I maximize my time in the sun, while making sure not to get sunburned. At this point in the summer (having gotten a modest amount of sun every day since the weather turned warm) I’m okay for up to about 40 minutes of mid-day sun. And I try to get that nearly every day.

Here’s one statistic, that I’ll let stand in for dozens of others about the advantages of sun exposure. The UK Biobank has data on health outcomes for hundreds of thousands of people. A researcher Jacobsen mentions went in and counted:

… in the fifteen years of tracking, a total of 40 people had died from skin cancer attributable to too much UV light, while 2,982 people had died from diseases attributable to a deficiency of sunlight.

The final third of the book is about artificial light, and makes the case that too much light at night is just as bad as too little light during the day.

Again, this is something that I figured out long ago. All the “sleep hygiene” stuff makes it clear that you want your sleeping space to be very dark, and there’s no doubt that getting enough high-quality sleep is probably the best thing you can do for your health, maybe even above good nutrition and plenty of exercise (both of which are easier to get if you’re sleeping well).

The prescription is almost trivially easy: Get outside at dawn. Get as much sunlight as you can without burning during the day. Within a couple of hours after sunset make your space as dark as possible and get some sleep.

In Defense of Sunlight: The Surprising Science of Sun Exposure by Rowan Jacobsen. Highly recommended.