Sun exposure to the skin is the human race’s natural, intended, most effective and most neglected source of vitamin D.Vitamin D sufficiency, along with diet and exercise, has emerged as one of the most important preventive factors in human health. Hundreds of studies now link vitamin D deficiency with significantly higher rates of many forms of cancer‚ as well as heart disease‚ osteoporosis‚ multiple sclerosis and many other conditions and diseases.
Because sunshine is a free commodity with no publicist or lobbyist, the Sunshine Vitamin Alliance is established as a coalition of right-minded physicians, individuals and organizations who advocate natural vitamin D production through regular, non-burning sun exposure.
There’s a lot of confusion surrounding sunlight and the production of Vitamin D. People commonly think that if the sun is up and they are outside in the sun, they are going to produce Vitamin D. This is not the case!
There are many reasons why you won’t make Vitamin D in the sun—even during the middle of the day. But most significantly, the sun cannot stimulate your production of Vitamin D if the sun isn’t high enough in the sky.
UVB Rays And Vitamin D
The reason is that UVB rays—and only UVB rays—catalyze the production of Vitamin D. Yet UVB is reflected and blocked by the atmosphere. The more atmosphere UVB rays have to travel through, the more UVB rays are prevented from reaching the surface of the earth; and the lower the sun is in the sky, the more atmosphere these UVB rays travel through. If the sun is low enough, UVB rays are completely blocked by the atmosphere before they even reach you, and Vitamin D production is not possible.
In addition to the atmosphere, clouds also block UVB rays, so if it is cloudy or overcast you probably aren’t going to produce any Vitamin D. Similarly, UVB rays are also blocked by ozone and pollution. In some cities excessive pollution can be enough to severely limit the amount of UVB rays reaching the ground and, therefore, the potential to make Vitamin D.
As a side note, UVB rays also don’t penetrate glass (or clothing). If you are in your car or behind a glass window Vitamin D production isn’t possible. UVB rays have to strike your exposed skin to make Vitamin D creation possible. Sunscreen lotion also blocks the production of Vitamin D.
UVA Rays And Sun Damage
Conversely, UVA rays pass relatively unfiltered through the atmosphere, so regardless of the angle of the sun or cloud cover, a high percentage of UVA rays are still reaching the surface of the earth. And UVA rays damage skin just like UVB rays. So even in the absence of UVB rays–like during the winter for much of North America, and when it is overcast–UVA rays are still present at high levels and still aging your skin.
Similarly, UVA rays penetrate glass and will still damage your skin while you are behind a window—such as during your daily commute or while you sit next to a window in your office. But UVA rays cannot stimulate Vitamin D production.
The Angle Of The Sun And Vitamin D Production
In order for the sun to stimulate your Vitamin D production, the sun needs to be at a minimum of about 50 degrees, or greater, above the horizon (90% would be directly overhead). Ideally, the sun should be as close to overhead as possible; the closer to overhead it is, the greater its potential for stimulating Vitamin D production (and the less time you have to be in the sun to produce a given amount of Vitamin D).
A good way to test if the sun is about 50 degrees above the horizon, or higher, is that your shadow should be slightly shorter than you are tall. If the shadow cast by your body is the same length, or longer, than your height you will not produce Vitamin D–even while your skin is exposed to direct sunlight. And this is under ideal conditions: clear skies without cloud cover or pollution.
Vitamin D Production And Skin Damage
Of course, UVB rays don’t just stimulate the production of Vitamin D; UVB rays also damage your skin. The more overhead the sun is, the more UVB rays you will absorb, and the more skin damage you will do. So you need to limit the sun exposure you do get.
Since Vitamin D production and sun damage go hand and hand, it’s a trade-off. With every second you are in the sun you are doing damage to your skin—even when you are producing Vitamin D. If you want to produce Vitamin D in the sun, do so when the sun is as close to overhead as possible, spend as little time as possible in the sun to produce Vitamin D, and then get out of the sun.
Also, you should have as much of your skin exposed to the sun as possible, and be at a perpendicular angle to the sun to maximize production. If the sun is directly overhead, for instance, you would lie flat on the ground, and when the sun is at an angle you would lie at the angle that allows you to directly face the sun.
It also doesn’t matter what part of your skin is producing your Vitamin D. It therefore is recommended that you expose the large areas of your body that don’t normally get very much sun, and cover the parts that are often in the sun (such as hands and wrists, face, neck, and shoulders) to protect them. In this way, you can maximize your Vitamin D production without further damaging the sensitive areas of your skin that are already most likely over-exposed. You can also alternate exposing your front and back (flip over halfway through your sun exposure) to decrease the damage to any one area of your body.
The one thing you are able to do to help prevent some sun damage from the sun, without blocking your production of Vitamin D, is to eat a lot of foods with natural antioxidants in them–like colorful vegetables and fruits. The product Sunsafe Rx–a pill with specific antioxidants shown to protect skin and eyes from the sun–can also help.
In general, aside from the periods when you are producing Vitamin D, make sure you protect yourself from sun exposure!
Vitamin D Production And Sun Exposure
Of course, even if you are producing Vitamin D, you don’t make an endless amount of it. After too much sun exposure your body stops producing Vitamin D, and excess sun exposure beyond this amount can even block Vitamin D production.
It has been roughly estimated that just 15 minutes of sun in the middle of the day in the summer, only a few times per week, can be sufficient for you to produce your complete Vitamin D needs. This is for people with fair skin in ideal conditions; darker-skinned individuals may need longer exposure time. The time of day (midday has the highest potential to stimulate Vitamin D production), altitude (higher altitudes increase production potential), and cloud cover and pollution (both decrease production potential) also impact the time it takes to produce Vitamin D. You can find some websites and phone apps that will help you calculate Vitamin D production more precisely. Just understand that the longer you are in the sun the more skin damage you will sustain.
Vitamin D Testing
If you want to be sure you aren’t Vitamin D deficient, you can get tested. If you’re low, you can supplement with extra Vitamin D3, then get tested again a few months later to see if your levels have changed. Adjust your Vitamin D intake accordingly. And follow your doctor’s advice.