Carnosine (beta-alanyl-L-histidine) is a dipeptide of the amino acids beta-alanine and histidine. It is highly concentrated in muscle and brain tissues.

Studies have shown that it can be used as an effective dietary supplement for people with autism, potentially improving such areas as auditory processing, speech & language skills, motor skills, and socialization. However, supplemental carnosine may increase corticosterone levels, which can explain the hyperactivity sometimes seen in high doses. Researchers in Australia, Britain, and Russia have also shown that carnosine has a number of antioxidant properties that may be beneficial.

Carnosine has been proven to scavenge ROS (radical oxygen species) as well as alpha-beta unsaturated aldehydes formed from peroxidation of cell membrane fatty acids during oxidative stress. It can oppose glycation and it can chelate divalent metal ions. In particular, some studies have produced evidence of beneficial effects of N-acetyl carnosine in treating cataracts of the eyes.

Typical vegetarian diets are thought to be lacking in carnosine, but whether this has a detrimental effect on vegetarians is controversial.