Who can resist a study that shows stress really does make your hair turn grey? Sadly the latest paper from Emi Nishimura has not found a link between, say, your office environment and the number of your colleagues sporting salt and pepper hairstyles.

Rather, in the latest issue of Cell, Nishimura and colleagues report that ‘genotoxic stress’ from ionising radiation damages DNA in the melanocyte stem cells that give mouse hairs their colour.

“It is estimated that a single cell in mammals can encounter approximately 100,000 DNA damaging events per day,” says Nishimura, of Tokyo Medical and Dental University (press release). “Once stem cells are damaged irreversibly, the damaged stem cells need to be eliminated to maintain the quality of the stem cell pools.”

Rather than causing the death of these stem cells, the damage makes them differentiate to form mature melanocytes instead of more stem cells, meaning nothing is left to dye the next growth of hair. So, mice exposed to radiation in their study turned permanently grey.

This may even be a mechanism to prevent damaged stem cells becoming cancerous.

“Greying may actually be a safety mechanism, that’s a cool twist,” David Fisher, of the Massachusetts General Hospital 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.”

Stress watch

“When an aging mouse’s lovely brown fur turns grey, she can now officially blame stress — at least, the kind of stress that damages DNA” – CBC

“If you’ve ever blamed your gray hair on stress, you weren’t far from the truth” – Science

“We’ve all heard that stress causes gray hairs. Now, new research suggests it’s true” – LiveScience

Image: Ken Inomata