Among its many functions, cystine helps create anti-oxidants in the body (1), and can help with hair health. However, none of these claims are well established. (2)
Cystine is the oxidized dimer form of the amino acid cysteine, and is considered nutritionally equivalent to cysteine. (3)
High cystine foods include pork, beef, chicken, fish, lentils, oatmeal, eggs, low-fat yogurt, sunflower seeds, and cheese. (4) The recommended daily intake of cystine is 4.1mg per kilogram of body weight or 1.9mg per pound. A person weighing 70kg (~154 pounds) should consume 287mg of cystine per day. (5)
Below is a list of the top 10 foods highest in cystine with the %RDI calculated for someone weighing 70kg (154lbs). For more high cystine foods see the extended list of cystine-rich foods.