If you're looking anxiously into the mirror at some new silvery strands, you're not alone. For millenia, gray hair has been a trial for those looking to retain their youthful appearance. Scientists have long been curious about what makes hair lose its color, and what role the aging process plays.
Hair Color Basics
In an article for Scientific American, University of Utah dermatologist Dr. Laurence Meyer explains that the color in your hair and skin comes from a pigment called melanin. The more melanin your hair and skin have, the darker they will be. Melanin is produced continuously by specialized cells called melanocytes, which are found in your hair follicles and beneath the top layer of your skin. Melanocytes transfer melanin to other specialized cells, called keratinocytes. These cells produce keratin, a protein that forms the building blocks of your hair, skin and nails. When keratinocytes die, they keep their melanin, maintaining your skin and hair's color.
Causes
Scientists are not entirely sure what triggers the graying process, or why some hairs turn gray and others aren't. But at some point in the aging process, melanocytes in hair follicles stop producing melanin, and then begin to decline in numbers. A partial loss of melanin turns hair gray, and a total loss turns it white.
According to Dr. Meyer, evidence suggests that genetics play a significant role in determining when your hair will turn gray, and how much of it will gray at any given time. You will likely start finding your first gray hairs at around the same age your parents or grandparents did.
Another potential factor in graying hair was discovered in a 2009 study performed by a European team of scientists. The team found that each hair follicle produces small amounts of hydrogen peroxide. Typically, an eznyme called catalase breaks the hydrogen peroxide down. The study suggests that diminished catalase leads to a buildup of hydrogen peroxide in the hair follicle, which eventually blocks the normal synthesis of melanin. The hydrogen peroxide then bleaches the hair from the inside out.
Misconceptions
It is widely believed that graying hair is caused or accelerated by stress. However, the scientific evidence produced by numerous studies has yet to support this idea. Scientists still haven't ruled out the possibility that stress plays a partial role in the graying process, but even if it does, the main reason people go gray is still believed to be genetic predisposition.
Time Frame
Caucasians tend to gray the earliest, followed by Asians and then Africans, according to a 2005 report written by the Journal of Investigative Dermatology and cited by The New York Times. There is further variation in graying among different ethnic groups. By age 50, 50 percent of the population is 50 percent gray or more.
Significance
Beyond vanity, understanding what causes otherwise healthy and hardy melanin cells to "switch off" can give scientists a better understanding of the aging process. It may also offer insight into how to deactivate destructive cells, such as those responsible for melanoma, a sometimes fatal form of skin cancer.
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