The below material is paraphrased from The UV Advantage by Michael F. Holick, PH.D., MD.
Sunlight Science
Sunlight consists of a mixture of electromagnetic radiation of various wavelengths. Ultraviolet, or UV radiation, consists of UVA, UVB and UVC rays. UVC is completely absorbed by the atmosphere. Although mostly absorbed by the ozone layer, some UVA and UVB rays still reach the Earth's surface. UVA radiation causes wrinkles while UVB is the form of radiation that reddens skin and causes sunburn. UVB also starts the reaction in skin that stimulates the production of vitamin D.
Exaggerated warnings about the perils of sun exposure are driving Americans to hide beneath long sleeves, floppy hats, wraparound sunglasses and to slather every square inch of skin that isn't covered with high-SPF sunscreens. The result of all this is to block out the sun that humans need to make vitamin D. The inescapable fact is that we humans have evolved in such a way as to be dependant on sunshine for life and health. Sunlight is as natural for human health as are food, water, oxygen and physical activity!
How Sun Exposure Benefits Human Health
Improves bone health
Enhances mental health (SAD, PMS, depression, general mood)
Prevents certain cancers
Improves heart health
Alleviates skin disorders
Decreases risk of autoimmune disorders, including multiple sclerosis, Type I diabetes mellitus, and rheumatoid arthritis
"Some is good" doesn't mean that "a lot is better"
According to Michael Holick MD., to make approximately 800 to 1,500 IU (International Units) of vitamin D, you need to expose 25% (face, hands, arms) of your body's surface area to 25% of 1MED two to three times per week at all times of the year when you can activate vitamin D in your skin. 1MED is the time it takes for your skin to turn pink.
So, if you get pink after being in the sun for 1 hour, 15 minutes would be enough time for you to get your dose of vitamin D for the day.
Sunscreen Safety
Sure, there are lots of sunscreen choices but does your sunscreen really protect you against UVA and UVB radiation? Is it safe for the health of you and the environment? Healthy Child has a great article on sunscreen safety that is relevant for adults as well as children. Please remember that despite the amazing features of your skin, ingredients from skincare products are absorbed in minutes through your skin and into your bloodstream. Skin Deep Cosmetic Safety Database is a wonderful resource for checking the safety rating of all skincare products.
After doing extensive research, I've chosen to use Badger sunscreen which provides strong protection for both UVA and UVB rays. The zinc oxide (not from nano particles) does tend to leave a slightly white residue but with some persistence you can get it rubbed into the skin. I don't mind the extra effort because I know this product is safe for me and my environment.
Be safe and enjoy the summer!
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