For something so universal, graying remains oddly mysterious.
Each strand of hair starts out nearly translucent, and its color is determined by melanin, essentially pigment dust. If it’s packed densely, you end up with dark hair. Leave only a few black and brown specks, and it appears blond.
Over time, the pigment-producing cells in each hair follicle tend to slow or shut down, turning hair gray, said Desmond Tobin, director of the Charles Institute of Dermatology at University College Dublin in Ireland. These strands tend to be stiffer and harder to control, growing 10 percent faster than pigmented hairs. Some people embrace them as a part of aging; others see them as a nuisance to be dyed, plucked or hidden.
But scientists aren’t sure what sets graying in motion or how much control we have over it. People can begin graying in their 20s or keep their natural color into their 80s. Although the process seems to be largely irreversible, researchers are finding that color can sometimes return — in patches and in darker roots.
For now, there’s no silver bullet to prevent or reverse graying, but experts are trying to untangle the issue and develop solutions.
What do scientists know so far?
Our hair doesn’t gray all at once, which is why you might notice stray silver strands and then experience a salt-and-pepper phase. Some hairs can even get lighter and darker again.
Each follicle is an independent unit, containing its own pigment-producing cells called melanocytes and a reservoir of replacement stem cells. As we age, these cells naturally accrue damage, like from stress or cellular wear and tear.
Hair graying usually starts when melanocytes in a particular follicle get compromised, but it becomes permanent when the stem cell reservoir is exhausted, said Emi Nishimura, a professor of aging and regeneration at the University of Tokyo. There’s research to suggest that, if the first process happens without the second, gray hair can be reversed.
In a small 2021 study, scientists collected hairs from people who had started graying and found distinct dark and white bands. Because hair grows roughly a centimeter each month, these bands offered a timeline, so researchers asked participants to chart their stressful experiences over the past year. Periods of higher stress lined up with lighter bands, and lower-stress periods corresponded with bands where color returned. In other words, dialing down stress levels appeared to reverse or slow hair graying.
Some people with gray hair have also spontaneously repigmented in patches after getting certain types of chemotherapy, radiation or immunotherapy. Experts suspect that, in these rare cases, the cancer treatments might coax dormant stem cells to rebuild functional melanocytes.
This research suggests that hair graying isn’t a completely linear process and that there’s a “window of opportunity” where pigment loss can be reversed, said Dr. Ralf Paus, a dermatologist at the University of Miami. How long that window stays open — and what could safely reawaken stem cells — is still unclear.
What can you do about gray hair?
Much of hair graying is genetic, said Dr. Jessica Shiu, a dermatologist at the University of California Irvine Health, so your parents and grandparents offer the best insight. Researchers have also found that graying usually starts in the mid-30s for white people, late 30s for Asian people and mid-40s for Black people.
But lifestyle choices might also make a difference. The strongest evidence points to quitting cigarettes and reducing your stress levels. Getting enough sleep and eating a healthy diet — with lots of antioxidants — might also limit the damage to your pigment cells, Dr. Shiu said, although the evidence is more indirect.
Premature hair graying has also been linked to low levels of iron and vitamin B12, but in the United States, deficiencies severe enough to affect hair pigmentation are rare, Dr. Tobin said. And there’s no evidence that supplements help with graying.
Be cautious about anti-gray supplements overall, Dr. Shiu said, since they’re often sold on promise not proof. Even if these supplements contain something helpful, there’s no evidence that taking a pill or applying a cream reaches the pigment cells deep inside hair follicles.
Although there are no medical treatments for gray hair, talk to your doctor about sudden or early graying, because a small share of cases are linked to prescription medications or diseases — and might be reversible. For example, some antiseizure medications, antimalarials, oral retinoids and muscle spasticity drugs have been tied to hair graying. Many cancer drugs also induce pigment loss, despite the rare cases of repigmentation.
Doctors can also distinguish between age-related graying and conditions that cause it. Thyroid and other hormonal disorders have been linked to early graying, as have autoimmune conditions that target hair follicles, like vitiligo and alopecia areata. Treatment can limit further pigment loss and sometimes allow color to return.
For most people, there’s not much you can do to prevent gray hair, but stacking small changes can help. “It’s not anything crazy — it’s just living a healthy lifestyle,” Dr. Shiu said.
Simar Bajaj covers health and wellness for The Times.
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