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.
The body manufactures carnosine from common dietary proteins, and for this reason there is no daily requirement of this substance.
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.
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.
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
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.
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.
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 weak evidence hints that oral carnosine might be helpful for cataracts , 24-29wound 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
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.
11. Kantha SS, Wada S, Tanaka H, et al. Carnosine sustains the retention of cell morphology in continuous fibroblast culture subjected to nutritional insult. Biochem Biophys Res Commun . 1996;223:278–82.
17. Schmidt AM, Yan SD, Wautier JL, et al. Activation of receptor for advanced glycation end products: a mechanism for chronic vascular dysfunction in diabetic vasculopathy and atherosclerosis. Circ Res . 1999;84:489–97.
27. Babizhayev MA. Rejuvenation of visual functions in older adult drivers and drivers with cataract during a short-term administration of N-acetylcarnosine lubricant eye drops. Rejuvenation Res . 2004;7:186–98.
31. Stvolinskii SL, Fedorova TN, Yuneva MO, et al. Protective effect of carnosine on Cu,Zn-superoxide dismutase during impaired oxidative metabolism in the brain in vivo. Bull Exp Biol Med . 2003;135:130–2.
33. MV, Aksenov MY, Markesbery WR, et al. Aging in a dish: age-dependent changes of neuronal survival, protein oxidation, and creatine kinase BB expression in long-term hippocampal cell culture. J Neurosci Res . 1999;58:308–17.
36. Butterfield DA. Alzheimer's beta-amyloid peptide and free radical oxidative stress. In: Gilbert DL, Colton CA, eds. Reactive Oxygen Species in Biological Systems: An Interdisciplinary Approach . New York: Plenum; 1999:609–638.
37. Carney JM, Starke-Reed PE, Oliver CN, et al. Reversal of age-related increase in brain protein oxidation, decrease in enzyme activity, and loss in temporal and spatial memory by chronic administration of the spin-trapping compound N-tert-butyl-alpha phenylnitrone. Proc Natl Acad Sci USA . 1991;88:3633–6.
40. Forster MJ, Dubey A, Dawson KM, et al. Age-related losses of cognitive function and motor skills in mice are associated with oxidative protein damage in the brain. Proc Natl Acad Sci USA . 1996;93:4765–9.
42. Huang X, Cuajungco MP, Atwood CS, et al. Cu(II) potentiation of Azheimer Ab neurotoxicity. Correlation with cell-free hydrogen peroxide production and metal reduction. J Biol Chem . 1999;274:37111–6.
43. Mark RJ, Lovell MA, Markesbery WR, et al. A role for 4-hydroxynonenal, an aldehydic product of lipid peroxidation, in disruption of ion homeostasis and neuronal death induced by amyloid beta-peptide. J Neurochem . 1997;68:255–64.
44. Munch G, Mayer S, Michaelis J, et al. Influence of advanced glycation end-products and AGE-inhibitors on nucleation-dependent polymerization of beta-amyloid peptide. Biochim Biophys Acta . 1997;1360:17–29.
45. Munch G, Schinzel R, Loske C, et al. Alzheimer's disease—synergistic effects of glucose deficit, oxidative stress and advanced glycation endproducts. Journal of Neural Transmission . 1998;105:439–61.
46. Smith MA, Sayre LM, Anderson VE, et al. Cytochemical demonstration of oxidative damage in Alzheimer disease by immunochemical enhancement of the carbonyl reaction with 2,4-dinitrophenylhydrazine. J HistochemCytochem . 1998;46:731–5.
54. Kendrick IP, Harris RC, Kim HJ, et al. The effects of 10 weeks of resistance training combined with beta-alanine supplementation on whole body strength, force production, muscular endurance and body composition. Amino Acids. 2008 Jan 4.
57. Pepper E, Farrell M, Nord G, Finkel S. Antiglycation effects of carnosine and other compounds on the long-term survival of Escherichia coli.Applied and Environmental Microbiology. 2010;76(24): 7925-7930.
Last reviewed August 2013 by EBSCO CAM Review Board
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