Why Does Hair Go Grey with Age?
- , by SANUSq Research team
- 8 min reading time
Almost all of us will go grey eventually — but what's actually happening in the hair follicle, and can anything really slow it down?
What gives hair its colour
Hair colour comes from a pigment called melanin, produced by specialised cells in the hair follicle called melanocytes. There are two forms — dark eumelanin and lighter pheomelanin — and the particular blend you inherit is what makes hair black, brown, red or blond. As each hair grows, these melanocytes inject pigment into the developing strand. Grey and white hair is simply what happens when that pigment supply falters: less melanin means grey, and no melanin at all means white. So greying isn't the hair "turning" grey so much as new hair growing in without its usual colour. Each follicle keeps its own timetable, which is why grey arrives strand by strand rather than all at once.
Research indicates that greying arises when melanin-producing melanocytes are lost from the hair follicle, a process linked to oxidative damage to these oxidative-stress-sensitive cells, with the timing of onset being strongly genetically determined (Shi et al., 2014).
Grey hair causes: why it happens with age
The main driver of greying is simply time. With each passing decade after about 30, a growing proportion of follicles lose their pigment-producing capacity — the melanocytes gradually become fewer and less active, and the follicle's own antioxidant defences weaken. One well-studied part of this is oxidative stress: over years, a build-up of reactive oxygen species (including hydrogen peroxide) accumulates in the follicle and damages the pigment cells, while the enzymes that would normally neutralise it decline. It's a natural, cumulative wear-and-tear process, which is why greying is so universal.
A comprehensive review concluded that hair greying is modulated by an interplay of genetic, oxidative, senescence-related, metabolic and nutritional factors, reflecting how many processes converge on the loss of follicle pigment (O'Sullivan et al., 2021).
The biggest factor: your genes
If you want to know when you'll go grey, look at your parents. Of all the influences on greying, genetics is by far the strongest — it largely sets both the age at which you start and how quickly it progresses. Some people spot their first grey hairs in their twenties; others keep their colour well into their fifties. It is also why comparing your timing with friends tells you much less than comparing it with your own family. This is also why the single most important thing to understand about "anti-grey" remedies is sobering: you can't out-supplement your genes.
Premature grey hair causes and the things you can influence
While age and genes dominate, a handful of factors are linked with greying earlier than your genetic clock would dictate, and some of these are at least partly within your control. Smoking is consistently associated with premature greying, likely through the extra oxidative stress it generates. Certain nutritional deficiencies — notably vitamin B12, and sometimes iron, copper or vitamin D — have been linked with early greying, which is one reason a genuinely unusual, rapid onset of grey in a young person is worth a chat with a doctor to check for an underlying cause; see food sources of vitamin B12. Certain medical conditions (particularly thyroid disorders) can play a role too. If you do raise it with a doctor, it is worth mentioning any other changes — energy, weight, appetite or digestion — since those are the clues that point towards the deficiencies and thyroid problems most often involved. Chronic stress is popularly blamed, and while the old idea of going grey "overnight" is a myth, there is some emerging science linking stress to pigment-cell depletion.
Can you reverse or prevent grey hair?
Here's the honest answer the marketing won't give you. For ordinary age-related greying, there is currently no proven way to reliably reverse or prevent it — no supplement, oil or "miracle" product has been shown to restore lost pigment across the board. The one genuine exception is worth knowing: where premature greying is driven by a correctable deficiency (such as B12) or a treatable condition, addressing that underlying cause can sometimes help, and there are scattered reports of pigment returning when a deficiency or an illness is resolved. So the sensible approach isn't to chase reversal products, but to look after the fundamentals that support healthy hair and slow needless oxidative damage: don't smoke, eat a varied diet rich in the vitamins and minerals hair depends on, and get any unusual early greying checked for a treatable cause. Dyes and colour-depositing products are a separate matter: they change how hair looks, not what the follicle is doing. Beyond that, greying is one of the most natural and universal signs of a life well lived — and there's a lot to be said for wearing it well.
Frequently asked questions
Why does hair turn grey with age?
With age, the melanocytes that produce hair pigment gradually become fewer and less active, and the follicle's antioxidant defences weaken, allowing oxidative damage to build up. Less pigment means grey hair; none means white. It's a natural, cumulative process.
What causes premature grey hair?
Genetics is the biggest factor in timing. Earlier-than-expected greying has been linked with smoking, certain nutritional deficiencies (notably vitamin B12, sometimes iron or copper), thyroid disorders and possibly chronic stress. Unusually rapid early greying is worth a doctor's check.
Can you reverse grey hair naturally?
For ordinary age-related greying, no — no supplement or product has been shown to reliably restore lost pigment. The exception is greying driven by a correctable deficiency or treatable condition, where addressing the cause can sometimes help. Be sceptical of "reversal" claims.
Does stress cause grey hair?
The dramatic idea of going grey overnight is a myth, but there is emerging evidence linking chronic stress to depletion of the follicle's pigment cells. Stress is unlikely to be the main driver of greying, which is dominated by age and genetics.
Can diet affect grey hair?
A varied diet supplies the vitamins and minerals hair depends on, and correcting a genuine deficiency (such as B12) may help where that deficiency is driving early greying. But no diet will override the genetic and age-related processes behind normal greying.
Should I see a doctor about going grey?
Normal greying with age needs no medical attention. But sudden, unusually rapid greying at a young age is worth discussing with a doctor, as it can occasionally point to a nutritional deficiency or an underlying condition such as a thyroid disorder.
Does plucking a grey hair make more grow back?
No. Each follicle grows one hair at a time, so pulling one out cannot recruit its neighbours — the hair that regrows from that follicle is simply grey as well. Repeated plucking can irritate or damage a follicle, so it is not a habit worth keeping.
References
- Shi Y, Luo LF, Liu XM, et al. Premature graying as a consequence of compromised antioxidant activity in hair bulb melanocytes and their precursors. PLoS One. 2014;9(4):e93589. PMC3973559
- O'Sullivan JDB, Nicu C, Picard M, et al. The biology of human hair greying. Biological Reviews. 2021;96(1):107–128. doi:10.1111/brv.12648
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