Going grey is normal.
Understanding it is useful.

Why hair turns grey

Hair colour comes from melanin, produced by cells called melanocytes in each follicle. Over time those cells become less active and eventually stop. The hair that grows through afterwards has little or no pigment, so it reads as grey, silver or white.

Timing is largely inherited. Most people notice the first strands somewhere between their thirties and fifties, though it can happen considerably earlier. It is not a health problem in itself.

What actually influences it

• Genetics. By far the strongest factor. If your parents went grey early, you probably will too.
• Age. Melanocyte activity declines gradually in almost everyone.
• Smoking. One of the few lifestyle factors with a consistent association in the research.
• Deficiencies. Low B12, ferritin, copper or vitamin D can play a part in some people. Worth a blood test if greying arrives unusually early.
• Certain medical conditions. Thyroid disorders and some autoimmune conditions among them. A GP is the right first stop.

Stress is often blamed. There is some laboratory evidence linking it to pigment loss, but for most people it is a minor factor next to genetics. We looked at what the research actually shows →

The honest position on reversing it

There is no product available today that reliably restores natural pigment to hair that has already gone grey. Where greying is driven by a specific deficiency or medical condition, correcting the cause can sometimes help. Otherwise, the practical options are colouring it or leaving it.

Treat any claim of guaranteed reversal with scepticism, and speak to a GP or dermatologist before spending money on a supplement.

We reviewed Bryan Johnson's hair protocol and the Blueprint range →
The full picture: what causes gray hair →

Grey or gray?

Both are correct. Grey is standard in the UK and most of the Commonwealth, gray in the United States. Same thing either way.