As the name suggests, milk proteins are the proteins found in milk. In particular, there are supplements based on whey proteins, the aqueous portion that separates from the rennet during the preparation of cheeses. Whey proteins help improve nutrition; it also appears to have a positive effect on the immune system. Their intake is proposed to improve athletic performance, as an alternative to milk in case of lactose intolerance, instead of infant formula or to supplement it, to combat weight loss and, in the case of HIV infection, to increase levels of glutathione.