Your head contains hundreds of thousands of follicles, and each follicle is charged with producing one hair. Before hair emerges, other cells known as melanocytes determine the hair's pigment. Once a hair's color is set, it's set.
When our hair turns gray, it's because of reduced amounts of melanin, and when hair is completely white, it's because it lacks melanin altogether. That's partly because of we lose the amount of stem cells that can become melanin-producing cells. But why?
Scientists aren't exactly sure. It could be those stem cells wear out or they become damaged. The support systems that help keep them working could also fail. But our hair follicles also simply produce less color as we/they age. So it makes sense that as each strand of hair dies and falls out and new strands regenerate in their place, their color will be lighter over time.
Genetics and Graying
But when — and if — you go gray is mostly influenced by your parents, as our genetics seem to have the most control over what comes out of each hair follicle. Scientists have been trying for decades to determine what's happening with our genes and cells when hair goes gray. Not only because they want to solve the mysteries of gray hair, but also because our hair might reveal information that's useful in treating other conditions related to aging.
In 2004, for example, researchers from the Dana-Farber Cancer Institute in Boston were studying melanoma, which involves an overproduction of melanocytes in the skin that can lead to skin cancer. While trying to learn more about the nature of melanocytes, the researchers found that hair might go gray as the supply of melanocyte stem cells is depleted. Even before those stem cells are completely gone, though, they begin to make errors, such as depositing the pigment at the wrong place in the follicle so they have no effect on the hair [source: Dana-Farber Cancer Institute].
The results of a 2009 Japanese study published in the journal Cell indicated that stress can in fact cause gray hair, but not the type of stress that comes with a teenage driver or an impending job interview. Rather, researchers found that genotoxic stress, in the form of ultraviolet light and chemicals, damages our DNA and could cause the depletion of those melanocyte stem cells.
Though research seems to indicate that we could stop the DNA damage by removing the genotoxic stress, the researchers estimate that just one mammalian cell is subjected to 100,000 such stressors in one day, making complete avoidance impossible.
Remove the Stress, Reverse the Gray?
But a small 2021 study from researchers at Columbia University Vagelos College of Physicians and Surgeons is the first with measurable evidence that links everyday stress to gray hair — and says it's even reversible. The researchers analyzed individual hairs from 14 volunteers. They compared the results with the volunteer's "stress diary," in which they tracked and rated their weekly level of stress. The researchers were surprised to discover that hair color was restored in some participants when stressors were eliminated.
"Understanding the mechanisms that allow 'old' gray hairs to return to their 'young' pigmented states could yield new clues about the malleability of human aging in general and how it is influenced by stress," study senior author Martin Picard, Ph.D., said in a press statement. Picard is an associate professor of behavioral medicine at Columbia University. "Our data add to a growing body of evidence demonstrating that human aging is not a linear, fixed biological process but may, at least in part, be halted or even temporarily reversed."
Take that, gray hair!
Originally Published: Jul 29, 2009
