Thursday 23 May 2013

Why Does the Sun Make Your Skin Darker

How does the sun affect people with dark complexions? 

            Dark complexions have both advantages and disadvantages when it comes to sun exposure. On one hand, dark skin is less likely to get sunburned and less likely to develop skin cancer. On the other hand, because dark skin naturally provides protection from the sun's ultraviolet rays, it prevents dark-skinned people from producing the necessary amount of vitamin D. When people with lighter complexions spend time in the sun, their bodies produce melanin, the pigment that gives color to skin and creates a tan. Melanin serves as a natural defense against UV rays, and people with dark complexions, especially those with olive, brown or black skin, already have a high concentration of melanin in their skin. This high concentration of melanin is responsible for their dark complexions and protects them from burning easily. In fact, as the amount of melanin increases, so does the natural protection from sunburn. But while a higher concentration of melanin provides some sun protection, it doesn't prevent skin cancer.
           
            But everyone needs some sun exposure to produce vitamin D. Vitamin D, also known as the "sunshine vitamin," helps the body absorb calcium, which maintains bone density and prevents osteoporosis And research shows that vitamin D may also help protect against chronic diseases such as diabetes, cancer, rheumatoid arthritis and heart disease . However, dark-skinned people's high concentration of melanin makes it more difficult for them to produce enough vitamin D. In fact, dark pigment in the skin reduces the skin's ability to synthesize vitamin D from sunlight by 95 percent. Lighter-skinned people can get enough vitamin D after 10 to 15 minutes of sun exposure a few times a week, but people with dark complexions may need five to 10 times more sun exposure to synthesize that same amount of vitamin D .
Even though vitamin D is important to your health, you should always wear sunscreen when spending long periods of time in the sun. If you're concerned about vitamin D levels, speak to a doctor or dietician. Keep reading to learn more about how the sun affects people with dark complexions.

Sunlight

Some of the sun's rays are beneficial, but others, such as ultraviolet rays, are hazardous. This radiation comes in three forms: ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). The earth's atmosphere filters out UVC radiation, but UVA and UVB affect you every day. UVB affects the top layers of skin, while UVA penetrates to the deeper layers. Your hair and your skin are negatively affected by these UV rays, although they appear to react differently.

Melanin

A pigment called melanin determines the color of your skin and hair. One form of melanin is a reddish-yellow color, while the other is brownish-black. The amount of each type of melanin you have in your skin and hair is genetically determined. Melanin protects your skin from the sun's harmful ultraviolet A and B rays by turning it a darker color. People with very little melanin often acquire no tan and are at the greatest risk for sunburn, premature skin aging and skin cancer. People with dark skin should also be cautious about sun exposure.

Skin

Your skin is the largest organ in your body. It protects you from the sun's harmful rays by producing the pigment melanin to darken your skin. Ultraviolet rays in sunlight destroy the melanin in your skin, which triggers your body to produce more and darker melanin. This melanin reaction to ultraviolet rays can cause sunburn or suntan. UV radiation also causes the skin to coarsen and wrinkle, making even young skin look and feel old.

Hair

Most of the hair on your body is made up of dead cells. Only the root is living, and once the hair emerges from the skin, the cells die. Melanin determines the color of your hair. People with very little melanin have blonde hair, while people with a great deal of melanin have black hair. Unlike the skin, which can regenerate melanin after UV damage, your hair is dead and can no longer make melanin. Sunlight kills the melanin in your hair and fades out the color, making it lighter and lighter. Your new hair will be as dark as before, since it contains the correct amount of melanin.

Precautions

Although light-skinned, light-eyed people are at the greatest risk from UV radiation, the Skin Cancer Foundation urges everyone to limit their exposure. Wearing sunscreens, broad-brimmed hats, tightly-woven, loose clothing and sunglasses helps fend off UV rays. Keeping out of the sun as much as possible is the best option. This is especially true from 10:00 a.m. to 4:00 p.m. in the Northern Hemisphere.

The American Academy of Dermatologists points out that tanning damages your skin irreparably, especially if you use a tanning bed or sunlamp while in your teens. These devices use the deeply-penetrating UVA rays to turn your skin darker, inuring your skin in the deeper layers. The damage to your skin may not appear until decades later.


Reference: http://www.livestrong.com, http://health.howstuffworks.com