為什么我們老了頭發(fā)會變白

為什么我們老了頭發(fā)會變白

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.

你有沒有想過為什么當你變老的時候頭發(fā)會變白?它的變化可以用科學來解釋。大多數(shù)人從30歲開始就有白發(fā)，男性最常見，因為他們比女性有更多的白發(fā)。以下是關于頭發(fā)相關問題以及為什么我們的頭發(fā)會變白的答案。

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.

大多數(shù)人在30歲時發(fā)現(xiàn)自己第一次頭發(fā)“變白”，通常是在兩鬢，然后是頭皮。很多人會想盡辦法把這些頭發(fā)遮住。

What Determines The Colour Of Hair?

什么決定了頭發(fā)的顏色?

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.

頭發(fā)顏色是由被稱為黑素細胞的細胞產(chǎn)生的，當毛囊在子宮內(nèi)發(fā)育時，黑素細胞會遷移到毛球中。黑色素細胞產(chǎn)生的色素與正在生長的頭發(fā)纖維結合在一起，形成一系列令人眼花繚亂的自然色調。

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.

頭發(fā)的顏色取決于兩組黑色素的存在和比例:真黑色素(棕色和黑色色素)和pheomelanins(紅色和黃色色素)。雖然這些色素比例的變化可以產(chǎn)生大量的顏色和色調，但兄弟姐妹的頭發(fā)顏色往往驚人地相似。

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.

金發(fā)孩子的頭發(fā)在七、八歲左右就會變黑。其機理尚不清楚，而且可能與荷爾蒙無關，因為皮膚變黑比青春期早幾年。

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.

初為父母的人經(jīng)常發(fā)現(xiàn)他們寶寶的第一層頭發(fā)比預期的要黑。直到8到12個月大的時候，他們的第一根頭發(fā)脫落并被替換，你才能清楚地看到他們的頭發(fā)顏色。

Growth

增長

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.

人類頭發(fā)的生長是周期性的。在生長期，毛發(fā)以每月1厘米的速度持續(xù)生長。生長素可以在頭皮上持續(xù)三到五年，產(chǎn)生的頭發(fā)可以長到36到60厘米長。

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.

在生長期的最后，毛囊停止生長，毛發(fā)停止生長，并保持三個月。在靜止期結束時，毛發(fā)脫落，毛囊空無一物，直到生長期的周期重新開始。

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.

遺傳因素似乎在決定我們什么時候變白方面很重要。同卵雙胞胎似乎在相同的年齡、頻率和模式下變白，但是我們還沒有確定控制基因。

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.

沒有證據(jù)表明頭發(fā)變白與壓力、飲食或生活方式有關。某些自身免疫性疾病，如白癜風和斑禿，會損害色素細胞，導致頭發(fā)變白。然而，這些情況是不常見的，只能解釋一小部分的灰色。

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.

早衰綜合癥如哈欽森早衰癥和沃納綜合征，會導致頭發(fā)過早變白，身體各個方面的衰老都在加速。惡性貧血、自身免疫性甲狀腺疾病或唐氏綜合癥患者也會出現(xiàn)過早白發(fā)。

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

那么，為什么色素不能恢復生長呢?

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.

在每個頭發(fā)周期的末尾，一些產(chǎn)生色素的黑色素細胞會受損并死亡。如果毛囊頂部的黑素細胞干細胞蓄水池能補充鱗莖，就能保持色素的生產(chǎn)。但是當干細胞的蓄水池耗盡時，色素的產(chǎn)生就會停止，頭發(fā)就會變白。

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.

科學家早已知道,為了防止頭發(fā)灰他們需要延長頭發(fā)中的黑色素細胞的生命-免受傷害或擴大黑素細胞干細胞水庫上或地區(qū)的毛囊,所以他們繼續(xù)補充流失的色素細胞。

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.

一組法國科學家發(fā)現(xiàn)了一系列新的制劑，可以保護頭發(fā)毛囊黑色素細胞在頭發(fā)周期結束時免受損害。這使得色素的生產(chǎn)可以在下一次頭發(fā)周期開始時重新開始。

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.

這種藥劑的工作原理是模仿一種叫做多巴胺互變擦除酶的作用。這種酶是頭發(fā)中自然產(chǎn)生的抗氧化劑，保護黑色素細胞免受氧化損傷。通過復制多巴胺互變擦除效應，黑素細胞新陳代謝和存活率提高。

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.

這些新藥劑正在被調配成一種可以作為血清或洗發(fā)水噴霧劑使用的產(chǎn)品。但是它們不會使灰白的頭發(fā)重新染色，也不會使產(chǎn)生頭發(fā)顏色的死細胞復活。相反，它們會保護你的黑色素細胞。

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

因此，對于那些無法在自己內(nèi)心找到擁抱白發(fā)的人來說，新的選擇就在眼前。