It's official, stress CAN make your hair go grey (but it also protects against cancer)

By Cher Thornhill

Stress really can make your hair go grey, scientists have found.

As the pressure builds, the stem cells that replenish your hair colour become damaged, leaving the tell-tale silver crown, a study has shown.

But the very visible sign of ageing appears to also have a beneficial effect - reducing the risk of cancer, a leading expert has claimed.

When scientists from Kanazawa University in Japan studied the effects of radiation and other chemicals on the fur of mice, they found that their coats greyed early.

This is because stem cells in their hair follicles were forced to mature, slashing the production of melanin - the chemical that gives colour to the hair and skin, the team explains in the journal Cell.

But Dr David Fisher, chief of the department of dermatology at Harvard Medical School, said that blocking these stem cells, which have damaged DNA, from dividing is also beneficial.

It could stop you developing a tumour, which is a ball of damaged cells that grow out of control.

‘Greying may actually be a safety mechanism,’ Dr Fisher told Bloomberg. ‘They’ve shown that this mechanism is actually removing damaged stem cells.

‘The good news is if you do find yourself greying, you’re probably better off not having those cells persist.’

He said the findings, reported in the journal Cell, have ‘far-reaching’ consequences because they suggest that early maturation and differentiation in other groups of stem cells could help prevent cancer as well.

Stem cells are the life source of the body, continually making copies of themselves which may differentiate into other cell types.

When those located in the hair follicles of mice stopped replicating, the animals soon ran out of that cells that create pigment in their fur.

Dr Fisher commented on the findings made by Dr Emi Nishimura at Kanazawa University in Japan, who he worked with at Harvard.

Dr Nishimura had previously discovered the stem cells within hair follicles and showed that their depletion during aging causes hair to turn grey.

For this study, her team exposed mice to radiation and drugs used in chemotherapy, then monitored changes in the colour of their fur as well as the status of their stem cells.

By looking at the hair follicles under microscopes, they saw when the stem cells turned into other cell types and linked the change to greying hair.

A similar mechanism may operate in people, she said.

The findings challenge existing theories about how the body tries to protect itself when it suffers genetic damage from radiation or other toxins, Dr Nishimura said..

People have speculated that cells die when their DNA is damaged by apoptosis, a scientific term for cell suicide, Dr Nishimura said.

This would stop damaged cells from growing uncontrollably as tumours.

But these findings suggest the body has another way to protect itself, she said.

‘Probably the tissue is trying to get rid of risky stem cell populations which have a lot of DNA damage,’ she said.

People constantly face a range of toxic agents that can damage their DNA from household and industrial chemicals, ultraviolet radiation from the sun and X-rays, and their effect on the body accumulates, Dr Nishimura said.

Dr Fisher said that the new findings ‘imply that age-related greying could be a result of accumulated DNA damage.’

It will take further experiments to prove the theory and to demonstrate that what’s true of stem cells in hair follicles is true of other types of stem cells.

Dr Nishimura said she is planning other experiments to investigate these possibilities.