why hair turns white when people get old?

As you get older, your body stops producing the cells it needs to make the melanin that give your hair its color. Melanin is the pigment, or coloring, in the cells of your hair and skin. Without the melanin to give your hair its dark color, it turns gray or white. Some people see gray or white hair even in their younger years. This usually happens because of changes in their genes, which means it runs in their family.