Hello, Sunshine!

Sunshine is essential for maintaining a healthy body. Research out of Sweden reports that going without sunshine has an impact on our health that is the equivalent of smoking a pack of cigarettes a day… not good!! Besides the potential for a vitamin D deficiency, there is a greater risk for numerous disorders, including autoimmune diseases, multiple sclerosis, and depression. In addition, UV light may be beneficial for the treatment of skin disorders, such as eczema and psoriasis.

Many wavelengths of the light emitted by the sun are used by our body to make some of the vital molecules that are required for healthy bodily function. This includes vitamin D and nitric oxide. When 7-dehydrocholesterol (a derivative of cholesterol) absorbs UVB light with a wavelength between 270 and 300nm and especially 293nm (though some sources say 290-315nm), provitamin D is produced. The production of nitric oxide, a chemical messenger with many functions, requires UVA light with a wavelength in the 315-400nm range. 

I see a lot of articles about the value of sun exposure, but not all sunshine is created equal. Medical recommendations suggest minimizing midday exposure and performing outdoor activities before 10am and/or after 3pm. However, UVB wavelengths are absorbed by the atmosphere in the early morning and late afternoon. The early morning and late afternoon sun exposure will not help with the intrinsic production of vitamin D but will contribute to UVA exposure

For UVB wavelengths to reach the surface of the Earth, the sun has to reach approximately 48 degrees above the horizon. At a latitude of 45 degrees North, this only occurs from April 1 to September 6. During the rest of the year, very little UVB reaches the planet’s surface at this latitude. Thus the middle of the day is the best time for sun exposure to obtain the desirable UVB wavelengths from April 1 through September 6 at 45 degrees North latitude.

The amount of time to spend in the sun depends on a number of factors: skin pigmentation (lighter skin requires less exposure), time of day, time of year, latitude, altitude, sunscreen usage, air pollution, and clothing worn.

Glass and plastic windows block UVB while allowing UVA to pass through. Since malignant melanoma appears to be more closely associated with UVA exposure than with UVB exposure, it is important to limit the amount of sunlight exposure through windows.

Our body self-regulates its intrinsic vitamin D production so there is a natural maximum concentration that can result from sun exposure. At this level, equilibrium is maintained with the vitamin being degraded as quickly as it is made. Of course, there are consequences of extended exposure to sunshine that are not desirable, such as sunburn and an increased risk of skin cancer. With dietary intake (including supplements), there is no internal regulation thus there is the possibility of overdosing on vitamin D leading to bone metabolism disorders and other associated mental and physical dysfunction.

Sunscreen may be an important consideration when there is the possibility of excessive sun exposure. But one must be very cautious about the actual sunscreen as the sunscreen chemicals are not regulated like foods and food additives. These chemicals are readily absorbed through the skin and can remain in the body for extended periods of time. Some of the chemicals in sunscreens are hormone-disrupting chemicals that can adversely affect our body’s hormonally-regulated metabolism. Zinc- and titanium-based sunscreens are safe to use.