by Uma Shankari

Created on: October 12, 2009

Sunlight is vital to almost every living organism. Sunlight kills microbes, and strengthens the immune and cardiovascular system. Sun gives us the sunny moods by fighting depression. Through assisting the synthesis of vitamin D in our bodies, it helps liver function efficiently and eliminate toxins. Sunlight, or vitamin D, stimulates the thyroid and helps one keep their weight under check. The sun's light is involved in the production of melatonin, a hormone secreted by the pineal gland in the brain. Melatonin levels rise when the sun goes down and fall when the sun comes up; this maintains the body's circadian rhythm.

Vitamin D is vital for our health. Vitamin D protects against cancer by discouraging out-of-control cell reproduction. Best of all, vitamin D fights multiple sclerosis and leukemia as well as the cancers of colon, breast, and prostate glands. Yet, sunlight has been vilified as a cause for skin cancers, and the once fashionable locales for beach lovers to lounge and get bronzed bodies have become less crowded. The cosmetic industry has seized the opportunity to make sunless tanning products.

Radiation from the sun

Ultraviolet (UV) radiation from the sun is most intense at the equator and at high elevations. It is divided into three wavelength bands ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). Only UVA and UVB rays reach the earth UVC radiation is completely absorbed by atmospheric ozone. UVA radiations are long- wave solar rays that penetrate skin deeply and are guilty of causing wrinkles.

UVB radiations are short-wave solar rays, which are more intense in summer and at noon time. Being shorter than UVA rays, the UVB radiations reach only the epidermis layer and cause most cases of sunburn. These rays are considered the main cause of basal and squamous cell carcinomas, which make up 95% of all skin cancers but are not serious or life-threatening. UVB can also lead to the more serious melanoma, which accounts for 75% of all skin cancer deaths.

Both UVA and UVB can lead to skin cancer, whether it is malignant or benign. Usually, melanoma skin cancer is caused by the UVA rays, as these are longer and can penetrate deeper skin layers. They are also likely to damage melanin-making melanocytes in the deeper layers of the skin, leading to melanoma.

Some points to remember:

* People with fair complexion and freckled skin that burns easily are more susceptible to skin cancer. Diets high in antioxidants and low in fats and alcohol can reduce the risk of melanoma by about 50%.

* Small children should be protected from long sun exposures as their defense system may not be well developed.

* There is no need to always use sunscreen. By blocking solar UVB radiation, sunscreens may cut off the vital source of vitamin D. Mid-day summer sun is the best source of UVB, and minimal exposure of 10-15 minutes without sunscreen can generate a day's worth of vitamin D.

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