Until modern times, human beings have lived mostly outdoors. Adapting an indoor lifestyle has resulted in an significant decrease in how much vitamin D we get from sun exposure. Numerous studies show that the population as a whole is suffering from chronic vitamin D deficiency. These studies indicate that the percentage is anywhere between 30 and 95 percent, depending on the demographics of the group being measured.
Ancient civilizations developed in subtropical climates, which made living outdoors year round a possibility. But as the human race migrated from subtropical to less temperate climates, this changed dramatically.
Sunscreens worsen the problem, because they prevent the manufacture of Vitamin D, even if you're outdoors for a long time. A sunscreen with even a minimum SPF factor of 8 reduces your body's production of vitamin D by 95%.
What's the Difference Between UVA and UVB radiation?
Ultraviolet light from the sun comes in two main wavelengths - UVA and UVB. It's important for you to understand the difference between them, and your risk factors from each.
UVA penetrates your skin more deeply and causes the most free radical damage. UVA rays are thought to be more responsible for wrinkling or premature aging of the skin. UVB helps your skin produce vitamin D.
UVA rays are quite constant during all the hours of daylight throughout the entire year. UVA rays can also penetrate clouds, so it's possible to get a sunburn even on overcast days. By comparison, UVB waves are lower in morning and evening and most intense at midday.
How Much Sun Exposure Do You Need to Maintain Normal Vitamin D Levels?
For most people living in the United States, two or three hours a week is adequate. The ironic thing is that the ideal time to get the maximum amount of vitamin D from sun exposure is in the middle of the day, exactly the time that you have been warned to avoid it. The trick is to stay out only as long it takes for your skin to get slightly pink (if you're light-skinned), no more. Any additional time in the sun won't produce any more vitamin D, since your body has a feedback mechanism that stops production after that.
Factors That Determine How Much Vitamin D You Get
The primary factor to consider when you get your vitamin D from sun exposure is the distance you live from the equator. If you live in the United States or Europe, the sun is not strong enough from about October through April to manufacture vitamin D. The further you go away from the equator, the shorter the vitamin D season gets.
Dark-skinned and Overweight People Have More Vitamin D Deficiencies.
African-Americans and other dark-skinned races need significantly more sun exposure to produce adequate vitamin D. Their skin has a higher melanin content which reduces the skin's ability to produce vitamin D from sunlight. A person with very dark skin has natural sun protection that's similar to a sunscreen with a SPF of 15-30.
People who are overweight also need more sun exposure than average people because some of the vitamin D gets stored in their fat and can't get out.
What About the Risk of Skin Cancer?
It's true that excessive exposure to sunlight increases risk of nonmelanoma skin cancer. But there's very little evidence that sensible, moderate sun exposure increases your risk. In fact, there's good evidence to suggest that it may actually decrease it.
Vitamin D Needs up to Two Days to be Absorbed.
It takes up to 48 hours for your body to absorb vitamin D from sunbathing. If you wash the exposed area with soap, you'll remove the oil-soluble vitamin D before it can be assimilated into your system. As long as you don't wash the exposed areas with soap, you'll retain the vitamin D.
How Much Sun Exposure Do You Need?
Your skin produces almost 20,000 IU vitamin D with just 30 minutes summer sun exposure in a bathing suit (without sunscreen). In the winter months, taking natural vitamin D supplements in the form of D-3 (cholocalcerifol) is imperative. Nutritionists are now recommending a minimum of 1,000 to 2,000IU a day for general preventive health.
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