BRUSSELS

Gray hair may be more than just a sign of aging as it could reflect the body’s natural defense mechanism against cancer, according to new research from the University of Tokyo.

A study published in Nature Cell Biology revealed that white hair results from damaged stem cells in hair follicles that self-eliminate to prevent the development of melanoma, a type of skin cancer.

Researchers led by Emi Nishimura and Yasuaki Mohri analyzed stem cells responsible for producing melanocytes – the pigment cells that give color to hair and skin.

They discovered that when these stem cells suffer serious DNA damage, they stop renewing themselves and self-destruct, preventing the damaged cells from dividing and spreading potentially cancerous mutations. This process leads to gray or white hair.

The process is driven by the activation of key signaling molecules that trigger cell self-elimination. However, under exposure to certain carcinogens, such as ultraviolet B radiation, the same stem cells may continue to renew and proliferate.

While researchers emphasize that gray or white hair does not directly protect against cancer, the study provides new insights into how the body's defense systems balance between cell death and uncontrolled growth.

"These findings reveal that the same population of stem cells can follow opposing fates (exhaustion or expansion) depending on the type of stress and microenvironmental signals,” Nishimura said in a statement. “This redefines hair graying and melanoma not as unrelated events, but as divergent outcomes of stem cell responses to stress.”