A different shade: The new research provides a molecular explanation of why people face grey hair in old age – and could even lead to a way of preventing it.

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SYDNEY: Researchers have discovered that hair turns grey with age because a natural build-up of hydrogen peroxide hinders the synthesis of melanin, our hair's natural pigment.

Their research, published online in The Federation of American Societies for Experimental Biology Journal (FASEB), provides for the first time a molecular explanation of why people face grey hair in old age – and could even lead to a way of preventing it.

Peroxide grey

"Not only blondes change their hair colour with hydrogen peroxide," said Gerald Weissmann, The FASEB Journal's editor-in-chief. "All of our hair cells make a tiny bit of hydrogen peroxide, but as we get older, this little bit becomes a lot. We bleach our hair pigment from within, and our hair turns grey then white."

The authors of the study, from Johannes Gutenberg University in Mainz, Germany and the University of Bradford in England, determined the greying process by studying cell cultures of human hair follicles.

"We now know the specific molecular dynamic that underlies this process," said biophysicist and co-author Heinz Decker.

Hydrogen peroxide, a known bleaching agent that is a by-product of metabolism, is found in normal hair at very small concentrations. The researchers showed that in ageing hair, hydrogen peroxide accumulates due to a lack of the enzyme responsible for breaking it down.

Enzymes in trouble

This build-up spells trouble for a hair follicle. Hydrogen peroxide attacks an enzyme called tyrosinase, which starts the production of melanin. The researchers showed that tyrosinase, and therefore melanin synthesis, is disabled when hydrogen peroxide oxidises a key amino acid on the enzyme.

The scientists also saw hydrogen peroxide inhibiting other enzymes that are needed to fix damaged proteins. Because of these two effects, the hair follicles gradually lose their melanin. Grey hair results.

The researchers hope their findings could eventually play a role in figuring out how to prevent greying – and possibly treating vitiligo a disorder of unknown cause in which melanin is lost in patches from the skin.

"This research is an important first step to get at the root of the problem," Weissmann quipped.