Why Do Older People Have Gray or White Hair?

Hair grows out of cells. The colour of the hair is determined by the melanin in the cell and the melanin is produced by the cells at the root of the hair. When people are young, their hair grows unceasingly. At the same time, the melanin is also constantly produced, giving colour to the hair. But when people get older, hair growth becomes slower. At the same time, the melanin produced by the cells at the root of the hair is also reduced, causing the new growth of hair to gradually become white.