Doctor's Best Glutathione + Milk Thistle contains Setria glutathione. Setria glutathione has been clinically shown to increase circulating levels of glutathione, the foremost protective and regulatory antioxidant naturally concentrated in all cells. Milk thistle extract provides silymarin, which increases levels of cysteine, one of the key amino acids that comprise glutathione, in the liver. Selenium is essential for facilitating glutathione's role in supporting energy production, detoxification and other fundamental life processes.