The Biology of Hair Pigmentation

Hair colour is produced by melanocytes, specialised pigment cells that sit in the hair follicle's bulb region. Melanocytes produce two types of melanin:

Eumelanin: Produces brown and black shades. Higher eumelanin content produces darker hair.

Pheomelanin: Produces red and yellow shades. The ratio of eumelanin to pheomelanin determines hair colour across the brown-to-red spectrum.

As each hair grows, melanocytes inject melanin granules into the growing keratin cells. When melanocytes reduce or cease pigment production, the hair grows out without colour: grey, silver or white.

Grey hair is not actually grey. The hair shaft itself is colourless (white). What appears grey is the visual mix of colourless new growth with remaining pigmented hairs in the same head of hair.

When Greying Starts: The Genetic Determination

The age at which greying begins is 70% to 90% genetically determined, based on twin studies and genomic research published in journals including Nature Communications and the Journal of Investigative Dermatology.

Average age of first grey hair by ethnicity (population averages):

  • White (European ancestry): Mid-30s
  • Asian (East and South Asian ancestry): Late 30s
  • African/Black (sub-Saharan African ancestry): Mid-40s

These are averages; individual variation within each group is wide. Premature greying (before age 20 in white and Asian individuals, before age 30 in Black individuals) warrants a medical check because early greying is associated with certain thyroid conditions, vitamin B12 deficiency and pernicious anaemia.

What Causes Earlier Greying

Genetics (Primary Factor)

If your parents greyed early, you are significantly more likely to do the same. This is the dominant factor and one you do not control.

Oxidative Stress

A 2009 study in The FASEB Journal showed that hydrogen peroxide accumulates naturally in the hair follicle with age and bleaches the melanocytes. The body's catalase enzyme breaks down hydrogen peroxide; catalase production decreases with age, allowing build-up.

External oxidative stressors (UV exposure, pollution, smoking) accelerate this process by generating additional free radicals that damage melanocytes.

Vitamin B12 Deficiency

B12 deficiency is the most consistently identified nutritional cause of premature greying. The deficiency impairs melanin synthesis by disrupting the conversion pathway that produces pigment molecules.

Populations at risk of B12 deficiency: Strict vegans (B12 occurs primarily in animal products), people with pernicious anaemia, those with Crohn's disease or coeliac disease affecting B12 absorption, and older adults with reduced intrinsic factor production.

A B12 supplement or dietary correction reverses B12-related greying in some cases if started before complete melanocyte depletion. This works only when B12 deficiency is the confirmed cause.

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Treatments That Do and Do Not Work

What Does Not Reverse Greying

Supplements marketed for grey hair reversal: Biotin, catalase supplements, copper supplements and melanin-stimulating products are all marketed with grey reversal claims. The available evidence does not support these claims for people whose greying has a genetic basis.

Catalase supplements: Despite the research showing catalase depletion contributes to greying, oral catalase supplements do not deliver the enzyme to hair follicles in meaningful concentrations. The digestive process breaks down oral catalase before it reaches the follicle.

Stress reduction: The relationship between stress and greying is biologically plausible (a 2021 study in Nature showed that acute psychological stress causes rapid melanocyte depletion in mice). For humans, the evidence is less clear and the effect is secondary to genetic predisposition.

What Actually Addresses Greying

Addressing confirmed deficiencies: B12, copper and folic acid deficiencies all have documented links to premature greying. Blood testing and supplementation for confirmed deficiencies produces the best potential for partial reversal or slowing of the process in these specific cases.

Hair colouring (temporary and permanent): The most reliable and effective cosmetic intervention. Covers grey completely and produces immediate results.

Embracing grey and managing tone: For those who choose to grow out grey hair, purple-toning shampoos and conditioners (developed for blonde and grey hair) neutralise the yellow undertone that appears in grey hair from sebum oxidation and environmental factors. Used once or twice weekly, they maintain cool, bright-silver tones.

Scalp micropigmentation: For people who prefer a shaved or close-cropped look, SMP matches the grey tone of surrounding hair and creates consistency across the scalp.