There are a few significant details you need to know and vitamin D and sun exposure. The vitamin D sunlight process depends on the time of year, time of day, amount of clouds and smog, your location, and the amount of pigment in your skin.
But wait – it get's even more complicated...and it involves that harmless looking bottle of sunscreen sitting in your medicine cabinet.
In order to understand vitamin D and sun exposure, you need to know that the sun produces three kinds of UV (Ultraviolet) rays: UVA, UVB, and UVC.
I'm not telling you this because I'm a science nerd (although I am). I'm telling you this because learning about vitamin D and sun exposure is important to your health.
UVB rays are the ones that our bodies use to make vitamin D. They are also the rays primarily responsible for making our skin tan or burn.
How much vitamin D our skin makes depends on the strength of those UVB rays (and the amount of pigment in our skin, but I digress...).
Most of us living in the U.S. can only make vitamin D during the summer months. UVB rays are too weak the rest of the year. Also important to know is that UVB rays are blocked by all sunscreens. Oh, and glass too.
UVA rays will tan you too, and are less likely to cause sunburns. But they prematurely age you because they penetrate deeply into the skin (think wrinkles, age spots, discoloration). Research has strongly linked UVA rays to skin cancers and immune system damage.
UVA ray strength does not vary according to the time of year or daylight hours (unlike UVB). It also easily penetrates through clouds and glass. And the vast majority of sunscreens do not protect against UVA rays (they only block UVB).
UVC rays are blocked by the ozone layer, so they don't make it down to earth. I just have it here to be complete (like I said, I'm a nerd).
So why is all of this important?
It might help explain why sunscreen users have a higher incidence of melanoma (the most dangerous type of skin cancer) than non-sunscreen users.
Sunscreen blocks the UVB rays so you do not burn, allowing you to stay out in the sun for longer periods of time. All the while the UVA rays are going right into your skin.
Sunscreens also do not allow you to make vitamin D when out in the sun. This is part of the reason why most of us are vitamin D deficient. Low vitamin D levels greatly increase our chances of getting many types of cancer.
So what can you do?
If you must spend lots of time in the sun, cover up with light, loose clothing. If that isn't an option for you, find a broad-spectrum sunscreen. These sunscreens are supposed to block UVA and UVB rays.
The only problem is that the FDA has no regulations in place to ensure that the products do what they say, so it's currently a leap of faith. Hopefully the FDA will step up soon and require testing to prove sunscreen company claims.
Do make an effort to get some vitamin D from the sun. With the right amount of sunlight (summer months between 10am - 2pm), our skin begins making vitamin D almost instantly.
In fact, we make most of it before our skin turns pink, so there is no reason to stay out in the sun longer than that. Sunburns are never a good idea.
As our vitamin D levels increase, more melanin (pigment) is made to protect us from getting too much. That's also why darker-skinned people need to spend more time (up to 6 times) in the sun to make the same amount as light-skinned people. The more melanin our skin has, the less vitamin D we can make.
It's true that we can store excess vitamin D in our fat cells for use over the colder months. But most of us don't even get enough sunlight exposure (minus sunscreen) during the warmer months to meet the body's current demands.
That's why I recommend vitamin D testing and taking a natural vitamin D supplement to get your levels up to where they should be. So just keep in mind - vitamin D and sun exposure - not the only way to go to get this critical nutrient.