Sun Exposure and Tanning
Key points:
Sun exposure destroys your collagen and makes your skin wrinkly
Diet plays an important role in UVB absorption
Everyone should get sunlight exposure, the right does varies widely
Sunlight is our main source of vitamin D
Melanin is your main regulator of UV radiation exposure
Sunburn is inflammation that releases free radicals which trigger the melanocyte signalling chemicals to start producing more melanin
The best source of dietary vitamin D is liver
Supplementing with vitamin D3 is safe and is necessary for the majority of the population in western society
Sun is your friend, use it as a tool for health and longevity
Excessive sun exposure is known to be one of the key causes of skin cancers. There has been a lot said about sunlight and cancer and this is not the focus of this article. We are going to explore the effects the UV radiation on our skin and how your diet affects it.
UVA vs UVB radiation
UV radiation from sunlight is one of the most potent collagen destructing mechanisms. Not surprisingly, the cosmetics industry is using this widespread fear to exponentially grow the multi-billion dollar suncare products market. Yes, the sun can damage your skin, but it doesn’t have to.
UV radiation in sunlight has little penetrating power, nothing like an X-ray for example. In fact, 95% or more UV is blocked by your rapidly regenerating epidermis, the outermost layer of your skin. The collagen beneath the epidermis absorbs much of the rest, depending on your diet, explains Dr Catherine Shanahan in her book Deep Nutrition. That remaining 5% may or may not lead to your sunburned skin.
There are three types of ultraviolet rays from the sun that reach the earth’s surface—UVA, UVB, and UVC. To put it simply, UVA rays are slower in wavelength and penetrate to the innermost layers of your skin’s epidermis. It is the UVA rays that tan your skin and create “immediate pigment darkening”.
It’s the higher frequency UVB rays that are attributed to sunburn (and delayed pigment darkening - more on this later) and cause most skin cancers. UVB rays are what most sunscreens protect you from. This isn’t to say that UVA rays can’t cause sunburn and cancer, it just takes a lot more exposure. UVB rays are also the ones that provide the energy your skin needs to make vitamin D, so you do need safe and regular exposure to it. Ozone stops most UVB from reaching the earth’s surface, only about 15% is transmitted.
The angle of the sun plays a big role in how much and what type of radiation passes through. The lower the angle, the amount of atmosphere crossed by sunlight is greater, thereby predominantly absorbing the higher frequency UVB rays rather than UVA. I guess my mom was right when she said the 6 pm summer sun was best if you want a good tan!
There is also UVC, which is the most dangerous one, but pretty much all of it gets blocked by the ozone layer. It is commonly used as a disinfectant in food, air, and water to kill microorganisms by destroying their cells' nucleic acids.
Diet affects your tanning
Inflammation can release the collagen-chewing enzymes and thus exacerbate the damage done by UV light. This eventually causes wrinkly skin. A balanced, collagen-rich, diet and moderate sun exposure will keep those enzymes in check. Of course, with excessive sun exposure, you will get inflamed skin even on the best diet.
Therefore, if your diet is full of inflammatory vegetable fats and sugars you should probably limit your sun exposure too. The more highly-oxidising polyunsaturated fats end up in your skin, the more readily you will get burned, releasing free radicals and exacerbating the situation even further with more extensive damage to the deeper layer of your skin. Not to mention building fear around sun exposure.
Sunlight recipe
Fearing sun exposure is a vicious cycle since the sun is literally our source of life. Just like plants, we use sunlight to grow. Plants use it for photosynthesis, and we humans use it to produce vitamin D.
We have evolved to thrive on sunlight exposure and I can’t imagine a healthy lifestyle without decent sun exposure. How much exposure is the right amount for you will vary widely depending on your latitude, altitude, time of year, climate, skin colour, your body’s ability to tan, and how much skin are you exposing to the sun.
For a healthy caucasian, a 20-minute summer sunbathing at around 35 degrees latitude (California, Malta, or Sydney for example) at midday would produce enough vitamin D to last for a week. After this much exposure to UV, we would want to shut off the supply as additional exposure might damage your collagen and vital nutrients including vitamin D.
Cloud cover plays a highly influential role in the amount of both UV-A and UV-B radiation reaching the ground. The more opaque the cloud, the less UV-B. However, thin cloud cover can be deceiving and cause severe sunburn.
Elevation and reflectivity of the surface both play a role in your UV exposure as well. The higher you are the less atmosphere light has to travel through thus more UVB reaches your skin. Likewise if you are spending time on a reflective surface like snow you will dramatically increase your UV-B exposure as it can reflect as much as 94 percent of the incoming UV radiation compared to 2-4 percent of snow-free lands. Ocean surfaces reflect about 5-8 percent.
How vitamin D is formed
When sunlight reaches your skin it hits the cholesterol molecules transforming them into a precursor of vitamin D, which gets fully activated in the liver and the kidneys. Vitamin D is not just a vitamin as the name suggests, it is a steroid hormone involved in numerous functions in the body. Incredibly, it modulates over 5% of your human genome! Among other things, you need vitamin D to metabolise calcium, without it, your bones would become weak and brittle. A child’s growth could be stumped with insufficient amounts.
Melanin regulates your UV exposure
Luckily, your skin has a great way of regulating UV exposure. Melanin, a skin pigment, does that for you. Our DNA regulates the baseline of pigment so well, that the skin tone of indigenous people can enable the prediction of their latitude of origin to within a few degrees. In the same way, your skin regulates your day-to-day melanin according to your exposure to UV radiation.
When UV radiation penetrates the outermost layer of dead cells it strikes the so-called melanocytes, cells in the skin and eyes that produce and contain melanin. They live in the outermost layer of skin where they can best protect the collagen underneath. They contain a signalling chemical that gets turned on by UV light and goes through a shape change. It can now fit into the enzyme that turns on the melanin production proteins in the melanocytes. This is your tanning system. Depending on your genetics, within minutes or hours, your skin begins to darken.
Sunburn and tanning
When you are exposed to excessive amount of UVB radiation at once it can cause inflammation in the skin, the familiar sunburn. This releases free radicals which eventually also trigger the melanocyte signalling chemicals, starting up the tanning process.
The increase in melanin is your body’s response to sunburn from UVB rays, to protect you from further exposure. This delayed pigment darkening usually begins two days after the exposure and lasts 10 to 14 days. The deepening of your tan may happen to coincide with the fading of your sunburn, but it doesn’t mean your sunburn is turning into a tan as many people think.
This delay is a clever design of our evolution. In higher latitudes, a hyper-tendency to tan wouldn’t allow people to make enough vitamin D.
Dietary vitamin D
In the modern lifestyle, we not only don’t get as much sun exposure anymore we also don’t eat as much liver. Liver happens to be the best dietary source of vitamin D, adds Dr Shanahan. Even other fortified foods usually don’t contain enough of this essential nutrient.
Only cholecalciferol supplements (also known as vitamin D3) can help us restore the needed amounts. Ergocalciferol (known as vitamin D2) is found in plants and is also a manmade vitamin D. In high amounts it can actually be toxic. On the other hand, it is really hard to overdose on vitamin D3, says the scientist Dr Rhonda Patrick. The highest recommended daily dose is 4000 IU, but studies have shown that you would have to consume hundreds of thousands of IUs on a daily basis to start experiencing dangerous negative effects.
We have to get our vitamin D one way or the other. If for various reasons there is no adequate sun exposure, diet is the next best thing. Diet is how Norwegians and Alaskans get it, by consuming liver oil from fish and other animals that did get enough sunlight.
Conclusion
On any diet, an excessive amount of sun exposure damages the deep layer of your skin and speeds up ageing. But on a bad diet, this damage is a lot worse.
Pace yourself when tanning. Excessive sunbathing on the first day of summer will cause a lot of damage to your deep layer of the skin. Ideally, before your summer vacation, you would get some base tan first.
As the legendary surfer, Laird Hamilton puts it, over the last few decades we have become the first culture in human history to fear the sun. All other cultures have not only embraced it but worshipped it. He actually shuns all sun-protective measures and trusts his body to protect him the best way it can.
I would add a word of caution here. No other culture travelled so far out of their location of genetic origin, we never had our ozone layer as damaged as we do today, and our diet has never been as poor and toxic as it is for the majority of the population. So caution and moderation are still advised. Maybe your DNA is not as ready for the harsh Australian or Subsaharan sun as you would like it to be?
And what about sunscreen? Well, this is a big topic that deserves its own article. Coming up next.
In any case, humans have evolved to live with and thrive on sun exposure. It is your powerful tool for health and longevity. Use it wisely.
Resources:
Deep Nutrition by Catherine Shanahan MD, chapter 16
https://earthobservatory.nasa.gov/features/UVB/uvb_radiation3.php
Huberman Lab podcast with Rhonda Patrick (from 1:17:00)