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Scientists have discovered that stress is one factor in turning our hair grey, white or silver - at least, in mice. Stem cell biologists from Harvard University in USA conducted series of tests on mice to ascertain effects of stress on rodents. The scientists injected the mice with ingredient found in chili peppers that gives them their heat. The compound made mice stressed. This caused hair-colouring pigment in mice to go into overdrive as reaction to stress and deplete colour-regenerating stem cells. This caused mice's hair to rapidly turn white. Lead researcher, Professor Ya-Chieh Hsu, said: "The detrimental impact of stress that we discovered was beyond what I imagined."

People have wondered for centuries about link between stress and greying hair. It is believed that France's Queen Marie Antoinette's hair turned white night before she was beheaded during the French Revolution in late-eighteenth century. More recently, we have witnessed locks of presidents and other world leaders quickly lose color. The strains of leadership seem to go to roots of things, especially hair follicles. Professor Hsu said the loss of pigment-regenerating stem cells cannot be reversed. She said: "Once they're gone, you can't regenerate pigment any more. damage is permanent." Worryingly, she hypothesised that stress could be responsible for accelerating aging process.

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