The Definitive Guide to Sun Exposure
The ancients prayed to it. Farmers relied on it. The seasons depend on the earth's tilt toward it. The sun is always up there, shining down, filling the world with light and heat, sending down powerful rays of energy that scatter across the surface, sneak through windows, penetrate otherwise dark caves. You can't avoid it, unless you shut yourself inside, draw the blinds, and close your eyes.
That's what we're supposed to do: avoid it, right? "Any amount of sun exposure is unsafe," according to the experts, and will give us skin cancer. They tell us it's a toxin. If we have to be outside, we'd better slather on the sunscreen, wear a hat that shields our entire body, and avoid the harsh midday sun at all costs.
And yet, for hundreds of thousands of years of human evolution, we couldn't avoid it all the time. We were exposed to the sun when we hunted, when we gathered. When we fished, dug, fought, climbed, and explored. The intensity of our sun exposure varied according to the climate, the latitude, the time of year, and we weren't out there tanning, but it was always around. Exposure occurred to some degree on a daily basis. We are adapted to the sun, like most other life on earth.
We aren't just able to withstand the sun. We can derive vital benefits from our exposure to it. We need the sun in a direct way.
Today I'm going to tell you why we need sun exposure, what the benefits are. I'm going to tell you how to make it safe, how to avoid sun damage, and the best time of day to do it. I'll discuss too much sun and too little. I'll give you safe ways to block the sun and reveal the unsafe ways to avoid.
Benefits of Sunlight
First, what’s so good about sunlight? The benefits of sunlight include:
Vitamin D
Nitric oxide
Circadian rhythm entrainment
Immune health
Cognitive function
Eye health
How does this all play out?
Vitamin D
Sun exposure causes the skin to produce vitamin D, a "pro-hormone" that regulates sex hormone production, immune function, bone, dental, and heart health, cancer prevention, and gene expression—to name a few functions. In other words, it's one of the foundational compounds in the body, an extremely vital substance.
We can get it from food or supplementation, but getting it from sunlight is auto-regulatory. It's extremely hard to overdose on sun-induced vitamin D production, whereas you can overdo supplemental vitamin D (although even that is hard).
Nitric oxide
Nitric oxide modulates the function of our endothelial system—the veins and arteries. Nitric oxide literally widens blood vessels and arteries, thus increasing blood flow to tissues (and the amount of nutrients that blood carries to those tissues). It even reduces blood pressure, improves our cardiovascular health, and is extremely important for our overall health, well-being, and physical performance.
It turns out that sun exposure increases nitric oxide production in the body.1
Circadian rhythm
We need exposure to light at certain times of the day in order to regulate our sleep-wake cycle – our circadian rhythms. Without daytime/morning light, or with too much evening light, our internal clocks—and general health—go awry. Getting outside in the sun (even in winter) as early as possible is an effective and quite possibly necessary way to establish a healthy circadian rhythm. Plus, the more sunlight you get in the first half the day, the more resistant you will be to circadian disruption by artificial light at night.
Immune health
Sunlight doesn't just improve immune health by way of increasing vitamin D. It also has direct, immediate effects on immune function: increasing hydrogen peroxide production by and motility of T cells in the skin. T cells can use hydrogen peroxide to engulf and destroy pathogens, and increased motility improves their ability to move around and find pathogens to destroy.2
Cognitive function
This study can't determine causation, but high sun exposure is strongly linked to better cognitive function among Chinese elderly and we have reason to believe there's a real effect here.3 For one, the vitamin D you produce in response to sunlight does boost cognitive function, particularly in the elderly (that's been tested in clinical trials using vitamin D supplementation).4 There are vitamin D receptors in the brain, and vitamin D is used to manufacture sex hormones which are involved in brain function.
Two, bright natural light is a powerful source of natural blue light, which increases alertness and productivity during the day. Three, among people with depression, exposure to sunlight improves cognitive function.5
Eye health
Most people only think about sun exposure in terms of skin health, but it can also play an important role in the health and function of our eyes. This makes sense when you think about evolutionary precedent: just like humans evolved without chemical sunscreens blocking the sun from reaching the skin, we never wore sunglasses preventing the light from hitting our eyes. If our skin is adapted to a given level of sun exposure, so too are our eyes. As it turns out, children who get inadequate outdoor time throughout their early lives have an increased risk of myopia.
Avoiding Sun Damage and Practicing Sun Safety
Sun exposure offers many benefits, and the conventional wisdom that sunlight is a toxin is clearly incorrect, but it's not completely harmless. There is such a thing as excessive sun exposure. Skin cancer can happen. Burning occurs. These are bad. How can you avoid sun damage?
Avoid burning.
Sunburns are just bad. They shouldn't happen. And if they do happen, damage has occurred. Sunburn history is a strong predictor of skin cancer risk. This means watching your exposure time, but it could mean finding shade, wearing hats, putting on clothing, or even wearing sunscreen. More on that last one in a later section.
Get full sun, not window-filtered sun.
Getting a window desk isn't the same as being outside in the sun. Windows filter out the UVB and allow the UVA to pass through. This has two major problems. First, UVA without UVB degrades vitamin D and fails to produce any more. You need UVB to make vitamin D. Second, UVA promotes melanoma while UVB protects against it.
Get good sleep.
Our resistance to the sun follows a circadian rhythm, with our defenses strongest in the first half of the day. So you might not want to go tanning after an all-night bender, nor do you want to get too much UVA-rich sun in the late afternoon when your defenses are down.
Chronic over acute.
You know who's less likely to get melanoma? The person with "occupational" sun exposure—the lifeguard, the surfer, the outdoor laborer. You know who's more likely to get melanoma? The person with "intermittent" sun exposure—the holidayer spending a couple weeks baking on a beach in Hawaii every year, the indoor office worker who tans for hours on the weekend. The intermittent type is more likely to get sunburned, more likely to get too much sun in a single dose, and more likely to end up with melanoma. The occupational type is less likely to burn, more likely to get the right amount of sun day in and day out, and less likely to end up with melanoma.6
Daily low/moderate-dose sun exposure is a better choice than infrequent high-dose sun exposure.
Remove seed oils and eat long-chain omega-3s.
A study out of Australia found that adults with the highest serum concentrations of DHA and EPA had the least “cutaneous p53 expression.”7 High levels of cutaneous p53 expression indicate skin damage; low levels indicate the skin is protected from the sun. The more omega-3s in your serum, the more protection from the sun you enjoy. And although serum omega-6 content didn’t seem to correlate with high p53 activity, my speculation is that serum omega-6 content passed a critical threshold.
Because it's so prevalent in the modern Australian (and overall global diet), even “low” levels are likely still above the threshold for increased susceptibility to sunburn. Going higher than that threshold won’t make things any worse, and it won’t show up in the statistics. Drop those seed oils, though, while getting an equal amount of omega-3s? I bet you’d see some incredible UV-resistance.
Eat polyphenols and carotenoids.
By eating lots of colorful plants and animal foods, you apply "edible sunscreen." For instance, eating a high-carotenoid diet protects the skin against UV damage, and lycopene, the active constituent in tomatoes (more active eaten with fat and cooked), has similar effects.8 The animal carotenoid astaxanthin, found in salmon and shrimp (and flamingo meat, if you can get it), may also offer protection against UVA.9
Polyphenols in general tend to increase the skin's antioxidant capacity, as do vitamins C and E.10 Anthocyanidins, found in red wine and berries, also protect against skin cancer.11 My picks? Berries, red wine, cooked tomatoes (tomato sauce, paste, ketchup), carrots, paprika, pastured egg yolks, sockeye salmon, shrimp form the basis of a good sun-resistance protocol.
Get early morning sunlight.
In a stunning example of the elegance of nature, early morning sunlight is rich in infrared light, which prepares your skin for subsequent UV exposure in the afternoon by enhancing its UV resistance.12 This protective effect of infrared light lasts for 24 hours, and it can come from either morning sunlight or an infrared light device, like a sauna.
Get the right amount of sun for your skin type.
Fair-skinned and red-haired? You need far less sun to get the vitamin D and other benefits you need, and you have far less leeway before damage occurs. Dark-skinned and living at a northernly latitude, like England? You might need to take supplemental vitamin D to get what you need.13 Even Indian men living in India may need at least an hour of sun to maintain optimal vitamin D levels.14
When is Sun the Strongest?
This is a common question, but it's not really the right one. The sun is technically strongest at midday when it's pumping out the most UVB and UVA rays. That's also when you have the most potential to make vitamin D, which depends on the UVB content. High UVB produces vitamin D, which protects against UVA-related damage and actively kills melanoma cells.15 High UVA in the absence of UVB promotes skin damage. Having both at the same time elicits a protective effect, or at least mitigates the damage of either alone.
Even though UV intensity is highest at midday, that's arguably the safest time to get sun because it's the best way to get balanced sun exposure.16
If you go mid morning or late afternoon, you'll get too much UVA and too little UVB. Just make sure to get only as much midday sun as you need. For the lightest-skinned among us, 10 minutes of full body exposure at noon should be enough.
Skin Protection
The internal and lifestyle "sunblocks" detailed above form the foundation of your skin protection regimen, but sometimes you need actual sunscreen. The problem is that the majority of mainstream sunscreens use chemical UV filters rather than physical UV filters. Chemical sunscreens come packaged with serious human health and environmental concerns, so I do my best to avoid them.
When I know I'm going to be in the sun for long enough that I risk burning, I choose a mineral sunscreen that contains zinc oxide or titanium dioxide (non-nanoparticle) as the active ingredient. Yes, mineral sunscreens often leave you looking like Casper the Friendly Ghost, but I prefer that to the endocrine-disrupting and possibly carcinogenic ingredients used in chemical sunscreens. For help picking the best sunscreen, the Environmental Working Group offers a comprehensive resource.
Okay, that's it for today, folks. If you have any other questions, comments, suggestions, or concerns, leave them in the comments! And share this post so others can find it.
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* This blog reflects my personal views and opinions and isn’t intended as medical advice, but I hope it will be informative and inspiring as you pursue a healthy, fulfilling life.
In 2013, I was new to Primal and recall reading that seed oil elimination enables one not to burn. Even though MDA had dramatically improved my life with its dietary education, I still thought, “right; and pigs will fly.” Well, pigs flew.
I had no sunburn all summer that year, in southern CA. In Miami in October, I spent a long day on the beach and had no burn. I realized MDA was right, again. My daughter now lives in Hawaii, and I’ve still had no burn. With no sunscreen. Since 2012. I used to be white and red, a full employment act for dermatology. Now I’m brown.
Thanks for sharing this, Mark. My oncologist told me that nicotinamide 500 mg twice daily (sometimes called niacinamide) is very protective during sun exposure.