How glutathione lightens skin ?

Glutathione is one of the popular whitening power now a days. We can find these already in different drugstores .I asked myself ,how this glutathione can lightens my skin? Glutathione inhibits the metabolism of melanin.The metabolic pathway reverses its course,going to the synthesis of light pigmented melanin instead of synthesizing dark-pigmented melanin.How much lighter can it make ? Glutathione lighten up the color of the skin just like lighter than birth color.Altering the birth color means changing one's DNA.