L-carnosine, not to be confused with L-carnitine, is a substance manufactured in the human body, made by combining the amino acids alanine and histidine. The highest levels of carnosine are found in the brain and nervous system, the lens of the eye, and skeletal muscle tissue. Its exact function in the body is not known.

Requirements/Sources

The body manufactures carnosine from common dietary proteins, and for this reason there is no daily requirement of this substance.

Therapeutic Dosages

Among advocates of carnosine, there is a controversy regarding whether the proper dose is 50–150 mg per day or nearer to 1,000 mg daily. However, until carnosine has actually been shown to have any medical benefits, this argument cannot be settled.

What Is the Scientific Evidence for Carnosine?

Like numerous other substances, carnosine has antioxidant properties, meaning that it neutralizes dangerous, naturally occurring substances called free radicals.22,23

Free radicals are thought to play a role in many illnesses. And, on this basis, many antioxidant substances have been studied for potential health-promoting properties. Some websites claim that carnosine acts as an antioxidant in a unique way, fighting the “second wave” effects that follow attacks by free radicals. However, there is no meaningful evidence to support this theory or the hypothesis that such an effect, if it truly exists, would provide any health benefits.

Anti-Aging

Carnosine is widely marketed as an anti-aging nutrient. There are numerous studies that hint carnosine might help slow various aspects of aging.1-20 The quality of these studies, though, is too low to provide any reliable evidence for benefit.1-20

Autism

There is some very preliminary evidence that carnosine may be helpful for children with autistic spectrum disorders.21 In a double-blind, placebo-controlled trial, 31 children with autism were given either carnosine (400 mg twice daily) or placebo for a period of 8 weeks. The children given carnosine showed significant improvements compared to those given placebo.

Brain Disorders

Carnosine has been studied in Parkinson’s disease. In a small controlled trial, adding carnosine to the diet of people being treated for Parkinson’s disease improved their symptoms.58 There is also weak evidence that carnosine may be helpful for Alzheimer’s disease and other forms of dementia.31-50 Carnosine can be found in the olfactory tissue, which is responsible for our sense of smell. Because of this, some researchers have suggested that carnosine should be administered through the nose (rather than by mouth), especially considering that people with Alzheimer’s disease often have problems with their ability to detect odors.57,60 This use for carnosine and this method of administering it are in need of further study.

Sports Performance

It has been suggested that taking supplements of the amino acid alanine can raise carnosine levels in muscle, and, in turn, enhance sports performance. In one small trial, 26 men were randomized to receive 6,400 mg daily of carnosine or a placebo over the course of 10 weeks.54 The men then went through an exercise training program, and their physical fitness was assessed after a 10-week period. Researchers, though, did not find any significant differences between the two groups.

Other Conditions

Other weak evidence hints that oral carnosine might be helpful for cataracts,24-29 wound healing,30 conditions of the digestive tract,53,56 and various forms of heart disease, such as atherosclerosis (hardening of the arteries).51,52 For example, one study found that carnosine may interfere with the development of low density lipoproteins (or “bad” cholesterol).55

Safety Issues

The use of carnosine has not been associated with any significant side effects. However, the body deploys a range of enzymes, called carnosinases, to break down carnosine. There may be a reason for the presence of these enzymes, and overcoming them by providing large amounts of supplemental carnosine could conceivably cause harm in some as-yet unrecognized way. Maximum safe doses in young children, pregnant or nursing women, or people with severe liver or kidney disease have not been established.