So we haven't yet found a cure for cancer—or even the common cold. But medical science may have just figured out another very important piece of the human puzzle: why we go gray. And the explanation, published recently by a team of European researchers, could lead to even more discoveries that might soon put your colorist out of business.
For many years, scientists have suspected that hair turns gray over time because some kind of naturally occurring "toxin" interferes with melanin's ability to saturate hair shafts with color. (Melanin is the substance produced by the body that colors hair, skin and eyes.) They noticed, for instance, that when chemotherapy patients start to regrow their hair, it initially emerges white, then turns gray before eventually returning to its original color. It seemed that once the strong anticancer chemicals cleared the body, hair shafts were able to accept color again.
There were also controversial theories that free radicals (molecules created when your body breaks down certain foods or by environmental exposures like tobacco smoke) were "produced as part of the melanin synthesis," says Dr. Zoe Draelos, president of Dermatology Consulting Services in High Point, N.C., and that they were "interfering with the ability of hair follicles to make melanin."
But it took a team of researchers, led by Dr. Karin Schallreuter of the University of Bradford in Great Britain, an expert on natural pigmentation, to figure out the exact biological and chemical process. The main culprit, it turns out, is an excess of hydrogen peroxide, naturally produced by hair cells. Unlike the bottled stuff that creates bleach blondes, the hydrogen peroxide produced in your scalp bleaches your hair gray.
"This is a big breakthrough," says Dr. Gerald Weissmann, editor in chief of the Federation of American Societies for Experimental Biology journal, which recently published the study. Not only does it "explain the basic biology and chemistry of [hair] pigment," he says, it has the potential to help scientists learn more about the entire aging process, as well as the role of stress in aging. That's great news for sure. But Weissmann also thinks it could mean that the millions of women who use dye to cover their gray may soon be able to reverse time with a pill, shot or lotion. "Once you understand the process, you have drug target."
Hair cells in people of all ages produce some hydrogen peroxide. But in young people, it's quickly broken down into its harmless elements of hydrogen and oxygen by the enzyme catalase, which exists in every cell. As we get older, however, the hair cells produce smaller amounts of catalase, and less hydrogen peroxide gets broken down, Weissmann says. Another enzyme, methionine sulfoxide reductase A and B (MSR A and B), normally helps hair follicles repair the damage caused by hydrogen peroxide. But as we age, the levels of these enzymes also decline, and they can't do as much damage control. The combination of higher levels of hydrogen peroxide and lower levels of MSR A and B make it harder for the body to produce enough of another enzyme, tyrosinase, which facilitates melanin's transfer to the hair shaft.
"As the bleach piles up, the melanin doesn't work as readily," Weissman says. At first, it strips a little color from the hair, giving it a gray appearance. But over time, as the level of catalase continues to decline and the level of hydrogen peroxide increases, the gray gives way to white. "The whole mechanism is upset by too much hydrogen peroxide," which "is a very concentrated form of oxygen," Weissman says. "We need oxygen and sunlight to live, but they also bleach us. Maybe the best analogy is that we're like a color photograph fading to black and white."
The process described by the European researchers also explains why the hair inside the ears doesn't turn gray as quickly as the hair on the top of the head, Weissmann says. "That hair is not exposed to as much sunlight or oxygen," he said. But does that mean if you wore more hats, you wouldn't gray as fast? "No," says Weissman. "It's not just sunlight. The problem is more the indigenous oxygen than the external factors. Most of our defenses just wear out as we get older."
Genetics also plays a role. Some people are born without one of these key enzymes, and their hair turns white very early. More typically, however, the first gray hair appears while people are quite young. "Most people start graying to some extent in their 20 and 30s," says Dr. Paradi Mirmirani, a dermatologist specializing in hair at the Permanente Medical Group in Vallejo, Calif. "I recently saw an 8-year-old with pretty dramatic salt-and-pepper hair, but there was nothing else wrong with her. On the other hand, there are some people in their 50s who have barely any gray. There's a lot of genetic variation, and part of this relates to the fact that the length of a hair cycle varies for each person. In each lifetime, there are only so many cycles."
And what about the role of stress? After all, a few years spent in the White House (or raising a teenager) seem a sure source of gray. "Some studies have looked at the relationship between an increase in stress and graying, but it's been hard to pinpoint stress's effects," Mirmirani says. "Hypothetically, we think stress signals could increase inflammatory signals and that could lead to more hydrogen peroxide in cells."
Weissmann predicts that there will be more research in this area. "The idea that some people's hair turns white with fright is an idea worth exploring," he says. "Now we have a way to test the effects of stress on an isolated system. The great thing about the hair follicle is that it's more accessible than many other parts [of the body], and we can more easily look at the gene and the interaction of cells to better understand some of the basic parts of aging."
As to reversing the graying process, Weissmann says he expects researchers to focus on all three of the involved enzymes, as well as the role of antioxidants and free radicals. (Antioxidants are a defense system in your body that helps prevent free-radical damage to cells. These include several enzyme systems as well as nutrients supplied through diet, including vitamin E, beta-carotene and vitamin C.) But Draelos adds that it's probably going to take more than slathering the head in antioxidants to get rid of gray hair. "I think it's extremely unlikely that putting something like green tea on your head is going to make a difference," she says. "The hair follicle resides in the fat layer below the skin of the scalp. We would probably need to find a way to drive the antioxidants to that level, and that probably means it will need to be taken internally."
For example, she says, "we know that the best way to treat a scalp infection is with oral antibiotics" rather than topical applications. "Enzymes would probably have to be taken orally, but they are very susceptive to digestive juices of the stomach, and they are often broken down before they are absorbed. Maybe an injection would work better, but there's much more work that will need to be done before it reaches the market."
But when there's a market as big as this one, especially in our youth-obsessed culture, no one doubts that the solution will be aggressively pursued, and we may soon have a choice about whether we want to go gray or not. "I don't know how long it will take," says Mirmirani, "but I don't think it's that far away."