You may not like those strands of grey sprouting from your scalp, but going grey could protect you from cancer.

A University of Tokyo study finds that grey hair in mice reflects a clean-up system that reduces the risk of cancer.  Researchers note that this is also reflected in human skin tissue.

When stem cells that produce hair pigment get DNA damage, the body forces them out, leaving behind grey hair as evidence that dangerous cells were eliminated. Carcinogens like UV radiation can override your body’s response, allowing damaged cells to survive and form melanoma instead of grey hair.

So next time you see a grey hair, remember that it could be your body showing you that it’s ridding itself of dangerous cells.