为什么年纪轻轻就长白头发?
Why Does Hair Turn Gray at a Young Age?

Q. What causes hair to turn gray? Why do some people go gray at a young age? Is there any evidence that rapid weight loss, slow weight loss or intense exercise accelerates graying? I’ve noticed that women in dieting “after” pictures commonly have a new hair color, while older male marathon runners are more gray and haggard than average.

问：是什么原因导致头发变白？为什么有些人年纪轻轻就华发早生？有没有证据表明，快速减肥、慢速减肥或是剧烈运动会加速头发变白？我发现，在女性节食前后的对比照片中，头发颜色通常会发生变化，而年长的男子马拉松运动员比一般人有更多白头发，也更憔悴。

A. Hair goes gray as cells called melanocytes at the base of each hair follicle get damaged by disease, environmental exposures or simply age.

答：头发变白，是因为头发毛囊底部的黑素细胞(melanocytes)因疾病、暴露在某些环境中，或者单纯因为老化而受到了损害。

Everyone has some gray hairs throughout life, but the balance tends to tip in the 40s or 50s, with the rate of change varying by genetics, gender and ethnicity, said Dr. James Kirkland, director of the Robert and Arlene Kogod Center on Aging at the Mayo Clinic. Blacks tend to go gray later than Caucasians, with Asians falling somewhere in between. Women generally gray later than men. The age you go gray is determined primarily by genetics, so if one or both parents went gray at an early age, you would be more likely to go gray at a younger age as well.

梅奥医院罗伯特和艾琳娜·克哥特老龄化中心(Robert and Arlene Kogod Center on Aging at the Mayo Clinic)的主任詹姆斯·柯克兰(James Kirkland)博士说，每个人在一生之中都会出现白发，但变化通常发生在四五十岁的时候，而头发变白的速度和基因、性别和种族有关。黑人头发变白的时间往往比白种人晚，亚洲人则介于两者之间。女性头发变白往往比男性晚。你到了什么岁数时头发开始变白是由基因决定的，所以如果你父母其中一人或者双方的头发都是早早变白，那么你就很有可能在比较年轻的时候有白头发。

安德森·库珀37岁时的照片，摄于2005年。

Smoking can also accelerate color change, and early graying could be a sign of autoimmune, thyroid or heart disease. “If you’ve got heart disease and your hair is gray, it’s a sign of worse heart disease,” Dr. Kirkland said.

吸烟也可以加速头发变白，头发过早变白也可能是免疫、甲状腺或心脏疾病的征兆。柯克兰克博士说：“如果你有心脏病，而你的头发是白色的，这是心脏病比较严重的迹象。”

Some people held in concentration camps during World War II who were deprived of proper nutrition also went prematurely gray, said Dr. Wilma Bergfeld, a dermatologist at the Cleveland Clinic, who specializes in hair disorders. “Everything is determined by the health of the pigment-producing cell,” she said.

克利夫兰医疗中心(Cleveland Clinic)的皮肤科医生、威尔玛·贝格费尔德(Wilma Bergfeld)博士专门研究头发问题，她说，“二战”期间被关在集中营的一些人由于得不到适当的营养补充，头发很早变白。“它完全是由生产色素的细胞是否健康决定的，”她说。

Dr. Bergfeld said she doesn’t know of anyone who has gone gray because of weight loss or exercise. Most activities that are damaging to the hair, like rapidly losing more than 20 pounds or getting chemotherapy treatment, will cause hair loss rather than a change of color, she said.

贝格费尔德博士说，她没有听说过有人因为减肥或运动而头发变白。她说，大多数对头发有伤害的做法，比如快速减肥超过20磅（约9公斤），或接受化疗，它们会导致脱发，而不是头发颜色的变化。

Unfortunately, there are no medications approved to restore hair color, though in early testing of the anti-hair-loss drug minoxidil, Dr. Bergfeld said that she and other researchers noticed the drug sometimes also restored hair color, suggesting it was rejuvenating the melanocytes.

遗憾的是，尚没有药物证明可以恢复头发的颜色，尽管在防脱发药物米诺地尔(minoxidil)的早期试验中，贝格费尔德博士说，她和其他研究人员注意到，这种药物有时候也会恢复头发的颜色，这表明它能让黑素细胞恢复活力。

It’s not clear whether chronic stress turns hair gray. Although President Obama’s hair turned gray during his time in office, studies that have looked at stress and hair color have been inconclusive, Dr. Kirkland said. (He also aged from 47 to 55, a time when many people’s hair turns gray.) “The consensus is that stress possibly does it,” he said. “But that’s a gut feeling rather than convincing evidence.”

柯克兰说，尚不清楚长期的压力会不会让头发变白。尽管奥巴马总统的头发在他当政期间变白了，但观察压力和头发颜色的研究一直没有定论（柯克兰博士的年龄也处在很多人的头发都会变白的47到55岁之间）。“共识是压力可能会，”他说。“但这是一种直觉，而不是有说服力的证据。”

本文最初发表于2017年6月9日。

翻译：土土、陈亦亭