Cystine is an indispensable amino acid in the body and has many effects on the body: 1. It promotes cellular oxidation and reduction functions, makes the liver function vigorously, promotes the liver’s detoxification ability and has a protective effect on the liver; 2. It promotes the blood system’s haematopoietic function and promotes the proliferation of white blood cells; 3. It improves immunity, prevents the development of pathogenic bacteria and acts as a body barrier; 4. It can assist insulin and play a hypoglycaemic role in conjunction with insulin; 5. Cystine can release sulphuric acid when metabolised, generating physiological and biochemical reactions with other substances and strengthening the detoxification ability of the metabolic system; 6. Cystine can reduce the body’s ability to absorb copper, protecting cells and avoiding copper poisoning.