为什么我们老了头发会变白

为什么我们老了头发会变白

Have you ever thought why your hair turn grey when you grow old? Its change can be explain by science. And most people estiblish grey hair starting from 30, most commonly on male as they tend to have more grey hair than female. Here are answers about hair related questions and why our hair turns grey.

你有没有想过为什么当你变老的时候头发会变白?它的变化可以用科学来解释。大多数人从30岁开始就有白发，男性最常见，因为他们比女性有更多的白发。以下是关于头发相关问题以及为什么我们的头发会变白的答案。

Most of us find our first “greys” by the time we turn 30, usually at the temples, then later, across the scalp. Many people go to great lengths to conceal these locks.

大多数人在30岁时发现自己第一次头发“变白”，通常是在两鬓，然后是头皮。很多人会想尽办法把这些头发遮住。

What Determines The Colour Of Hair?

什么决定了头发的颜色?

Siblings often have strikingly similar hair colour. hans905/Flickr, CC BY-NC-SA

Hair colour is produced by cells known as melanocytes, which migrate into the hair bulb as the hair follicles develop in utero. The melanocytes produce pigment that is incorporated into the growing hair fibres to produce hair in a bewildering array of natural shades.

头发颜色是由被称为黑素细胞的细胞产生的，当毛囊在子宫内发育时，黑素细胞会迁移到毛球中。黑色素细胞产生的色素与正在生长的头发纤维结合在一起，形成一系列令人眼花缭乱的自然色调。

Hair colour depends on the presence and ratios of two groups of melanins: eumelanins (brown and black pigments) and pheomelanins (red and yellow pigments). While variations in the ratio of these pigments can produce an large number of colours and tones, siblings often have strikingly similar hair colour.

头发的颜色取决于两组黑色素的存在和比例:真黑色素(棕色和黑色色素)和pheomelanins(红色和黄色色素)。虽然这些色素比例的变化可以产生大量的颜色和色调，但兄弟姐妹的头发颜色往往惊人地相似。

Blond children tend to see their hair darken around the age or seven or eight. The mechanism for this is unknown and probably not related to hormones, as the darkening precedes puberty by a number of years.

金发孩子的头发在七、八岁左右就会变黑。其机理尚不清楚，而且可能与荷尔蒙无关，因为皮肤变黑比青春期早几年。

New parents often find the first coat of their baby’s hair is darker than expected. It is not until this first hair is shed and replaced, at around eight to 12 months of age, that you get a clear indication of their hair colour.

初为父母的人经常发现他们宝宝的第一层头发比预期的要黑。直到8到12个月大的时候，他们的第一根头发脱落并被替换，你才能清楚地看到他们的头发颜色。

Growth

增长

Human hair growth is cyclical. During the anagen phase, hair grows continuously at a rate of 1cm per month. Anagen can last three to five years on the scalp and produce hair that grows to between 36 to 60cm in length.

人类头发的生长是周期性的。在生长期，毛发以每月1厘米的速度持续生长。生长素可以在头皮上持续三到五年，产生的头发可以长到36到60厘米长。

At the end of the anagen phase, the follicle turns off, hair growth stops and remains off for the three months. Towards the end of this resting (telogen) phase, the hair is shed and the follicle remains empty until the anagen phase of the cycle restarts.

在生长期的最后，毛囊停止生长，毛发停止生长，并保持三个月。在静止期结束时，毛发脱落，毛囊空无一物，直到生长期的周期重新开始。

Losing Colour

失去色彩

Genetic factors appear to be important in determining when we turn grey. Identical twins seem to go grey at a similar age, rate and pattern, however we’re yet to identify the controlling genes.

遗传因素似乎在决定我们什么时候变白方面很重要。同卵双胞胎似乎在相同的年龄、频率和模式下变白，但是我们还没有确定控制基因。

There is no evidence to link the onset of greying to stress, diet or lifestyle. Certain autoimmune diseases such as vitiligoand alopecia areata can damage pigment cells and induce greying. However, these conditions are uncommon and can explain only a tiny fraction of greying.

没有证据表明头发变白与压力、饮食或生活方式有关。某些自身免疫性疾病，如白癜风和斑秃，会损害色素细胞，导致头发变白。然而，这些情况是不常见的，只能解释一小部分的灰色。

Don’t worry, stress won’t turn your hair grey. frankieleon/Flickr, CC BY

Early greying occurs in premature ageing syndromes such as Hutchinson’s-progeria and Werner syndrome, where every aspect ageing in the body is accelerated. Premature greying can also be seen in people affected by pernicious anaemia, autoimmune thyroid disease or Down syndrome.

早衰综合症如哈钦森早衰症和沃纳综合征，会导致头发过早变白，身体各个方面的衰老都在加速。恶性贫血、自身免疫性甲状腺疾病或唐氏综合症患者也会出现过早白发。

So, why doesn’t pigment production turn back on?

那么，为什么色素不能恢复生长呢?

At the end of each hair cycle, some pigment-producing melanocytes become damaged and die. If the melanocyte stem cell reservoir at the top of the hair follicle can replenish the bulb, this keeps pigment production going. But when the reservoir of stem cells is exhausted, pigment production stops and the hair turns grey.

在每个头发周期的末尾，一些产生色素的黑色素细胞会受损并死亡。如果毛囊顶部的黑素细胞干细胞蓄水池能补充鳞茎，就能保持色素的生产。但是当干细胞的蓄水池耗尽时，色素的产生就会停止，头发就会变白。

Scientists have long known that in order to prevent hair from going grey they would need to either prolong the life of the melanocytes in the hair bulb – by protecting them from injury – or expand the melanocyte stem cell reservoir in the upper or top region of the hair follicle so they continue to replace lost pigment cells.

科学家早已知道,为了防止头发灰他们需要延长头发中的黑色素细胞的生命-免受伤害或扩大黑素细胞干细胞水库上或地区的毛囊,所以他们继续补充流失的色素细胞。

A group of French scientists have identified a new series of agents that protect hair follicle melanocytes from damage at the end of the hair cycle. This enables pigment production to restart as soon as the next hair cycle begins.

一组法国科学家发现了一系列新的制剂，可以保护头发毛囊黑色素细胞在头发周期结束时免受损害。这使得色素的生产可以在下一次头发周期开始时重新开始。

The agents work by mimicking the action of an enzyme called DOPAchrome tautomerase. This enzyme is the naturally occurring antioxidant in the hair bulb that protects melanocytes from oxidative damage. By duplicating the effects of DOPAchrome tautomerase, melanocyte metabolism and survival improves.

这种药剂的工作原理是模仿一种叫做多巴胺互变擦除酶的作用。这种酶是头发中自然产生的抗氧化剂，保护黑色素细胞免受氧化损伤。通过复制多巴胺互变擦除效应，黑素细胞新陈代谢和存活率提高。

The new agents are being formulated into a product that can be applied as a spray-on serum or shampoo. But they won’t re-colour grey hair or bring back the dead cells that produce hair colour. Instead, they protect your melanocytes.

这些新药剂正在被调配成一种可以作为血清或洗发水喷雾剂使用的产品。但是它们不会使灰白的头发重新染色，也不会使产生头发颜色的死细胞复活。相反，它们会保护你的黑色素细胞。

So for those who cannot find it within themselves to embrace the salt and pepper look, new options are on the horizon.

因此，对于那些无法在自己内心找到拥抱白发的人来说，新的选择就在眼前。