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If you look back at the recent presidents here, you might notice a little trend.
回顾美国最近几位总统，你可能会注意到一个小趋势。
Reagan, Clinton, Bush and now even Obama.
里根，克林顿，布什，甚至是现在的奥巴马。
All looking a little more grey when they're coming out of that White House there.
他们离开白宫的时候头发都有点发灰了。
Is it a little salt with that pepper?
是因为工作太辛苦了吗？
Could it be as the ancient legend goes that having a stressful job causes graying hair?
是否真如传说那样，工作压力大会导致人头发变白呢？
Everyone, I'm Laci Green and this is dnews.
大家好，我是Laci Green，欢迎大家收看dnews。
Let's face it, we are obsessed with youth.
大家面对现实吧。我们确实是喜欢年轻的。
People have collective nightmares about one day waking up and seeing ourselves with a head full of gray hair.
大家都有这样一个噩梦，害怕哪天一觉醒来，就发现自己已经满头白发了。
It's terrifying.
那太可怕了。
Fortunately, gray hair has a quick fix called "hair dye".
幸运的是，我们有个快速处理白头发的速效救心丸，“染发剂”。
But that doesn't stop people.
然而，人们并没有因此满足。
They still want to understand how to stop those gray strands from popping up in the first place.
他们还想知道如何从根源上解决长白头发的问题。
The gray hair situation goes a little something like this.
长白头发的生理机制差不多是这样。
By default, your hair is sort of transparent whitish.
默认情况下，我们的头发是有点透明，有点发白的。
There are cells in your hair follicles called "melanocytes" that generate a pigment called "melanin",
但我们的毛囊里有一种叫“黑色素细胞”的东西，它们能产生一种叫“黑色素”的色素，
which then gives hair its color.
你头发的颜色就是这么来的。
Basically, the more melanin you have, the darker your hair.
大体而言，黑色素越多，你头发的颜色就越深。
So less melanin, the lighter your hair.
同理，黑色素越少，你头发的颜色就越浅。
Eventually, these melanocytes say, okay, I'm done, no more melanin for you.
终于，这些黑色素细胞说，就这样吧，我不干了，没有更多黑色素给你了。
And that's when you start to get gray hair, as follicle by follicle the melanocytes stop producing melanin.
也就是从这时起，随着一个个的毛囊停止产生黑色素，你开始长白头发了。
But what triggers the fall of the melanocytes?
但问题是，是什么引发了黑色素细胞的罢工的呢？
There are a few factors.
原因是多方面的。
The main one is genetics.
但最主要的原因是遗传。
If you come from a family where your parents or grandparents went grey early,
如果你来自一个父母或祖父母长白头发都比较早的家庭，
You're probably gonna go gray early as well.
那你很有可能也会早早地长出白头发。
On average, women start spotting some gray hair around 35 and men around 30.
平均而言，女性是35岁左右开始长白头发，男性是30岁左右开始长白头发。
But greying can begin as early as high school or as late as your 50s.
但长白头发这事儿说早能早到高中，说晚能晚到半百之年。
It's super variable and it really depends on both genetic and environmental contributors.
年龄变化范围特别广，说到底，遗传和环境都有影响。
For instance, smokers are four times more likely to go gray prematurely than non-smokers.
打个比方，抽烟人群过早长出白头发的概率高达不抽烟人群的四倍。
Some vitamin deficiencies can also affect hair color and so on.
缺乏某些维生素也会影响头发的颜色等等。
But what about stress?
问题是，压力呢？
Can living a stressful life cause you to go grey early?
生活压力大会让一个人过早长出白头发吗？
The answer is kind of.
答案是，有可能。
Stress itself does not actually cause hair to start growing out gray, so that part is a myth.
事实上，压力本身并不会让你的头发变白，所以，上述说法就是个传说而已。
Scientists have found that a more accurate relationship between stress and graying hair
科学家们发现，压力和头发变白这二者之间更准确的关系是
is that if you're predisposed to graying early, lots of stress could cause an early onset.
如果你有头发过早变白的倾向，过多的压力就会导致你提前进入长白头发的阶段。
The current thought is that stress can, one, cause some melanocytes to decline slightly earlier,
当前，科学家们的认知是：一、压力会导致部分黑色素细胞提前那么一点点衰老，
And, two, increase the likelihood of shedding hair, which then contributes to an increased likelihood of graying hair.
二、压力会提高头发脱落的可能性，继而提高头发变白的可能性。
Again, this is all based mostly but not entirely on your genetics.
不过，还是那句话，主要还是取决于基因，虽然也不全是基因说了算。
If you're not predisposed to graying, it's unlikely that stress will do much to change your hair color.
如果你没有头发过早变白的倾向，那么，压力是不太可能对你的发色产生太大影响的。
So add that to your stuff that's been proven wrong pile.
所以，你可以把压力会让头发变白的说法放到被证明是谬误的一边了。
And as for the presidents, well, yeah, if they're predisposed,
至于我们的总统，是这样的，如果他们有头发提前变白的倾向，
I'm sure governing one of the most powerful countries in the world doesn't help out with the stress levels.
我敢肯定，治理身为全世界最强大的国家之一的美国对缓解压力是没什么帮助的。
But I think part of why, it seems like the presidents are going grey
但总统们头发变白的原因，我个人的看法是
is because they're right in that going grey age and we typically have our eyes on them for nearly a decade.
他们本来就已经到了头发变白的年龄了，而在他们卸任之前，我们通常都已经关注他们10来年了，不白才怪呢。
All right guys, so how do you feel about graying?
好了，盆友们，你们对头发变白这事儿怎么看呢？
Are you planning to dye your hair or do you think that you will go au naturale?
你会去染发吗？还是会顺其自然呢？
Let me know in the comments below and be sure to subscribe so you can catch some more dnews tomorrow.
快在评论中告诉我吧。还有，不要忘了订阅，这样你就能看到我们明天的更新啦。
