Sunlight is important to a healthy lifestyle. Sunlight is the primary natural source of Vitamin D. Vitamin D is important in maintaining strong bones and a healthy immune system. Outdoor exercise improves our cardiovascular fitness. Sunny days make us happy. Sunlight may be important for health – both physical and mental – in ways we do not understand.
Overexposure to sunlight can produce sunburn immediately and skin cancers in the long term. Sunburn in childhood has the strongest association with lifetime risk of melanoma. Melanoma causes most skin cancer deaths. It is most common on the legs and back. Lifelong sun exposure can cause basal cell and squamous cell skin cancer. These growths continue to grow if not treated but kill infrequently and occur most commonly on the face, scalp (in men), hands and other areas exposed continuously to sunlight.
Sunlight (UV) damages genetic material (DNA), directly binding DNA strands together and causing mutations. If these mutations are not repaired, cancer can result. Children born without the ability to correct this specific damage die in early childhood from skin cancer unless kept completely out of the sunlight. Luckily, this is a rare problem.
Most human skin is protected from sunlight by color (pigmentation). Melanin is the pigment in skin. It forms a cap like an umbrella over the DNA in cells. Darker skin has up to five times the protection of lighter skin and a much lower risk of skin cancer. Lighter skin is better adapted to Northern Europe where sun exposure is minimized by northern latitude and cloudy days. Lighter skin will produce more Vitamin D at lower levels of sun exposure.
Flagstaff is high risk for skin cancer. Closeness to the equator, high altitude, sunny days and light skin color all increase risk.
We can decrease our risk of skin cancer with changes in our lifestyle. Sunlight can be avoided in the middle of the day when it is most intense. Tightly woven clothing and hats are the best outside protection. Sunscreen is also protective. Regular use can reduce pre-cancers, squamous cell skin cancer and basal cell skin cancer. Titanium dioxide and zinc oxide are pigments and not chemicals and function like skin pigment as a barrier to sunlight. Chemical sunscreens are clear and easier to apply. The sun protective factor (SPF) is a good indicator of protection. An SPF of 15 allows only six percent of cancer producing sunlight. An SPF of 30 allows about three percent. Higher than an SPF of 30 is not recommended unless exposure is anticipated to be intense and prolonged.
What can I do to prevent skin cancer?
- Prevent sunburn in childhood – protect your children from future melanoma.
- Decrease sun exposure in youth and young adulthood when sun exposure is often intense.
- Protect severely sun-damaged skin daily
What can I do for health?
- Regular sun exposure in moderation but not to chronically sun damaged skin.
- Older people are most vulnerable to excessive sun avoidance and Vitamin D deficiency. FBN
By Carl Bigler, M.D.
Carl F. Bigler, M.D., FAAD, is board certified in dermatology and dermatopathology with Northern Arizona Dermatology. Dr. Bigler has been practicing dermatology in Northern Arizona since 1995.