The Definitive Guide to Sun Exposure

definitive guide to sun exposureThe 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. “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 it. 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.

First, what’s so good about sunlight?

Benefits of 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

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.5

Daily low/moderate-dose sun exposure is a healthier 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.”6 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. 7  Polyphenols in general tend to increase the skin’s antioxidant capacity, as do vitamins C and E.8 Anthocyanidins, found in red wine and berries, also protect against skin cancer.9

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.10 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.11 Even Indian men living in India may need at least an hour of sun to maintain optimal vitamin D levels.12

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.13

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.

So 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.14 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. What’s wrong with chemical sunscreens?

Physical vs. Chemical Sunscreen

Many sunscreens use UV-filters like benzophenone and oxybenzone for their UV-blocking properties, but they also possess a hidden feature: endocrine disruption. Certain forms of benzophenone, for example, inhibit the action of thyroid peroxidase, an enzyme necessary for the production of thyroid hormone.15 Another study showed that application of sunscreen containing benzophenone-2 for five days lowered T4 and T3 thyroid hormones in rats.16 Later, researchers examined the estrogenic effects of another UV-filter used in sunscreen—octyl-methoxycinnamate—and found that typical amounts were enough to disrupt hormonal function and exert other, non-endocrine health effects when applied to rat skin.17 That might not a problem if UV-filters in sunscreen weren’t designed to be absorbed into the skin, and therefore the body, nor if every expert weren’t telling us to slather a quarter cup full all over our bodies at the first hint of sunlight. But they are: the only way the chemical sunscreens work is if they are absorbed into the skin—and into systemic circulation.

Another downside of chemical sunscreens is that they’re selective screeners. They tend to block UVB while allowing UVA passage. This blocks the tanning/burning effect, but it also blocks UVB-induced vitamin D production. And the worst part? It’s not even effective against the development of melanoma! In fact, one study found a positive association between sunscreen usage and melanoma incidence.18

Meanwhile, physical sunscreens are broad spectrum: they block both UVA and UVB. They can be unsightly because they don’t absorb into your skin, but they offer the most protection with the least toxicity.

Sunscreen Ingredients to Avoid

These ingredients are absorbed into the body, show up in your urine, have estrogen mimetic effects, and can often cross the blood brain barrier and cause neurotoxicity.1920 Some of the most common include:

  • Oxybenzone
  • Benzophenone
  • Avobenzone
  • Octocrylene
  • Homosalate
  • Octisalate
  • Octinoxate

For a full list of chemical sunscreen ingredients to avoid, check out the data from this paper.

Sunscreen Ingredients to Use

There’s only one that I can recommend whole-heartedly: Zinc oxide. It reflects light, offers the broadest-spectrum UV protection, and cannot absorb into the skin. This is why it stays white and doesn’t rub in.

Nano-zinc oxide does rub in, but that also comes with a price. You absorb some of it. It appears to be less harmful than the chemical sunscreens, though not completely.

Non-Toxic Sunscreen Brands

These are ones that hit all the requirements.

Badger Balm – All their products are good, but the sunscreens are the most renown. They are very thorough with the science behind their sunscreens, and they run regular tests to confirm the safety of their zinc oxide formula. Best of all, they’ve managed to minimize the whitening without increasing the potential for toxicity.

Raw Elements Eco Formula – Active ingredient is zinc oxide. It’s thick, but stays on well even with water exposure and activity. Not too whitening, either.

Kabana Skincare – Another good sunscreen source that uses zinc oxide. They’ve even got a formula with added vitamin D, presumably to make up for the UVB you’re blocking. Not sure if that actually works, but it certainly can’t hurt.

Mexitan – They don’t just make non-toxic, zinc oxide-based sunblock. They also offer recommendations for beach resorts and produce safe self-tanner.

Okay, that’s it for today, folks. With summer right around the corner and the sun beginning to show, now’s the time to start getting smart, safe sun exposure—and after today’s post, I believe you are prepared to do so.

If you have any other questions, comments, suggestions, or concerns, leave them down below!

TAGS:  sun

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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13 thoughts on “The Definitive Guide to Sun Exposure”

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  1. I haven’t used sunscreen in decades, mainly because I don’t like having those chemicals on my skin. I would rather just cover up and put on a hat if I’m going to be in the sun long enough to get burned. My skin isn’t damaged at all, and I don’t have a lot of wrinkles.
    It’s mind boggling how widespread–and how totally absurd–the fear of sunshine has gotten to be. I’ve talked to people who think they need to wear sunscreen 24/7/365, rain or shine, and regardless of whether they’re going to be outside or not.

  2. Thank you. I was just looking for information about sun exposure on your website yesterday. Perfect timing!

  3. I’m curious if the primal community has a go-to list of dermatologists who aren’t afraid of the sun. I would like to go occasionally to get a skin check, but every time I’ve been in the past it’s been to a pasty-white unhealthy looking doctor advising me to stay out of the sun. Any go to ideas?

  4. A note about sunglasses: Some folks should be wearing them. For instance, a lot of the fisherman in native tribes would go blind at a fairly early age from staring into the water for long periods of time. The Eskimos had really cool bone sunglasses, with little slits they would use, so they would not go snowblind. After my own daily sun exposure, I’m not averse to putting on my shades.

    1. That’s very interesting. Would love more info on this. I’ve always hated wearing sunglasses, but definitely don’t want to go blind!

    2. Great fact! I never knew shades were this important. However, it gets difficult for me to wear them with spectacles so I haven’t really used them in years.

  5. I cannot see the claim that early morning sunlight is better or richer in IF light. Here is morning sun and elsewhere in the world (not far away, around the corner) is is mid morning sunlight and so on….Sounds non-logical….

    The sun shines normally, but it is our location determining if it is morning or evening sunlight.
    Please explain! Thanx!

    1. I am not sure but guess it has to do with how the arrays refract through the atmosphere.

  6. All of those sunscreen ingredients to avoid also kill aquatic life, not just in the ocean, but in lakes and rivers too.
    Another option to add to that list is Stream2Sea. Its a small Florida company with decent prices.

  7. Do the same rules for sun exposure apply if you have had melanoma in the past?

  8. Does this imply that taking a daily UVB only sunbed throughout the Autumn and winter (avoiding redness/ burning) might be advisable for those of us in the higher northern latitudes, such as the UK? Or does the UVB need to be balanced by UVA (and therefore does UVA have any unique beneficial effects?)

  9. How do clouds influence the amount of the UVB?
    I wonder if it is worth to have sun exposure under cloudy sky.

  10. What do you think of the new “safe” korean chemical sunscreens that have not been approved yet in the U.S.?