In this week’s installment of Medical Discovery News, UTMB’s Norbert Herzog and David Niesel report that Japanese researchers have discovered that hair turns grey as a defense mechanism against disease. Hair becomes gray when people age because melanin is no longer formed. The researchers were looking at the stem cells that produce melanin and what kind of effect DNA damaging agents had on them. In mice, these agents caused enough DNA damage to result in premature grey hair. The researchers made a new discovery that cells with DNA damage can be eliminated as a whole, which is how the body protects itself from cells that could become cancerous. MDN airs locally at 10 a.m. Saturday on KUHF.