Many of you will have heard of melanin, the pigment that gives colour to our skin, hair and eyes. When it comes to hair, melanin comes in two types, the dark eumelanin (brown and black) and the light pheomelanin (red and yellow) that both blend together like a paint palette to form various shades of hair. Melanocytes are pigment cells in our hair follicles that produce melanin. As we age, melanocytes die off until there aren’t any cells left to produce colour. Reduced pigment levels lighten hair colour, turning hair grey.
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Pigment production turns on and off in rhythm with the hair cycle. This cycle is divided into three phases: The anagen phase (lasting from three to five years, with hair growth of one centimetre per month), catagen phase (a transitional phase of ten days) and telogen phase (a dormant phase of three months, where hair is shed and the hair follicle remains empty until the next anagen phase). Grey hair results when a pigment which turns off at the end of a hair cycle fails to turn back on at the start of the next cycle. The failure to do so may be due to the fact that some melanocytes are damaged and die at the end of each hair cycle. When this happens, a melanocyte stem cell reservoir at the top of the hair follicle can continue pigment production by replenishing the hair bulb, but when even this reservoir has been exhausted, pigment production stops altogether.
On average, hair begins to go grey between the ages of 30 and 40, and greying occurring before 40 are considered prematurely greying. This can be due to damage to the hair from excessive exposure to UVA and UVB rays from the sun and hydrogen peroxide, a chemical in most hair dye and toothpaste. In the case of UVB exposure, stem cells would move from the hair follicles to the skin to repair the injury to the skin. Stem cells would move without replicating themselves, which leaves fewer stem cells in the hair follicles at the injury site, so hair growing out of these hair follicles would be lighter.
Iron deficiency, such as in anaemic patients, can also cause premature greying. This is because iron produces the proteins that feed hair follicles, ensuring healthy growth of hair and melanin production.
Vitamin B-12 deficiency is another factor to premature greying, because vitamin B-12 can boost the production of melanin. Having thyroid problems may mean quicker greying, since elevated levels of the thyroid hormone may disrupt the timing of the hair cycle, causing an abnormal number of hair to shift to the telogen (dormant) phase of the hair cycle.
Greying is, however, primarily genetically determined, which is evident from hair turning grey at a similar age, rate and pattern for identical twins. This means one’s hair will turn grey at about the same time it did for their parents or grandparents. However, the controlling genes for this is yet to be found. Contrary to popular belief, stress does not cause your premature greying.
There is research being done to reverse the effect of, or delay, greying. Vitamin B-12 supplements were found to re-colour grey hair. A group of French scientists have identified a new series of agents that protect melanocytes from being damaged at the end of the hair cycle, allowing pigment production to restart at the beginning of the next cycle. This won't re-colour grey hair, but it would protect the melanocytes from damage, improving their survival.
It is however important to realise that such research is being done as a result of demands being driven by consumers of the age-shaming society. Age-shaming is often promoted by the beauty industry to make people, especially women, buy more youth-preserving products. However, it is important to realise that greying is a natural phenomenon that comes with age and is in fact, nothing to be ashamed about.