While we've all blamed our fading locks on stress, in reality, there is no proven link, "Hair grays when cells stop producing the color pigment, melanin," says Jeffery Miller, associate professor of dermatology in Penn State's College of Medicine. "It's a natural part of the aging process."
There are three phases to the hair growth cycle, Miller explains: anagen, catagen, and telogen. During the anagen, or active, stage, hair grows rapidly. Each strand grows for two to four years before entering the catagen phase, a transitional state. After about two weeks, hair reaches its final resting point, the telogen stage. After several months of rest, the inactive older hairs are pushed out by new hairs. "The telogen hairs are those that you find in your comb or at the bottom of the bathtub," says Miller. "The average person loses 50 to 100 of these strands during daily activities."
"As we age, each cycle gets shorter and shorter," describes Miller. "And, in turn, the shortened cycles accelerate the breakdown of melanin." The faster hair falls out, the quicker pigment cells stop working.
Melanin is found in skin, eyes, and hair. The amount of pigment produced by melanocyte cells determines color. Brunettes have more melanin than blondes, and white hair has no melanin at all. "Gray hair is a mixture of pigmented hair and white hair," Miller notes.
"The process normally begins in one's 30s, but gray hair may become visible as early as one's teens," says Miller. When it starts has much to do with genetics, he notes. "Look at your father, your mother, your siblings. If they went gray early, chances are that you will, too."
While Americans spend billions of dollars every year on hair dye products to cover gray, the breakdown of melanin is...