Reviews and meta-analyses
A meta-analysis pools the numbers from several trials. A narrative review summarises the literature in the authors' own words. Both depend on the quality of the trials they include, and this page states those limits for each one.
Two things to check on any review page here: who wrote it and how the studies were chosen. Some carnosine reviews were written by authors who hold patents or company links, for example in the eye-drop literature, and some meta-analyses pooled small trials with different doses and durations. Each entry says so where it applies.
Meta-analyses
8 listed, newest first.
- Protective and Healing Effects of Zinc L-Carnosine on the Oral Mucosa: A Systematic Review and Meta-Analysis
Severe oral mucositis was less frequent with zinc L-carnosine under a common-effect model (OR 0.48, 95% CI 0.32 to 0.72) but not under a random-effects model (OR 0.44, 95% CI 0.18 to 1.06).
Meta-analysisHumansWith zinc (as polaprezinc / zinc-L-carnosine) - Efficacy and Safety of Polaprezinc-Based Therapy versus the Standard Triple Therapy for Helicobacter pylori Eradication: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Adding polaprezinc to triple therapy improved eradication in intention-to-treat analysis (OR 2.01, 95% CI 1.27 to 3.21, p = 0.003) and per protocol (OR 2.65, 95% CI 1.55 to 4.54, p = 0.0004).
Meta-analysisHumansWith zinc (as polaprezinc / zinc-L-carnosine) added to triple therapy - Effect of Carnosine or beta-Alanine Supplementation on Markers of Glycemic Control and Insulin Resistance in Humans and Animals: A Systematic Review and Meta-analysis
In human studies, supplementation reduced HbA1c (mean difference -0.91%, 90% CrI -1.46 to -0.39), HOMA-IR (SMD -0.41, 90% CrI -0.82 to -0.07) and fasting insulin (SMD -0.41, 90% CrI -0.77 to -0.07).
Meta-analysisHumansWith beta-alanine (carnosine precursor) included alongside carnosine - Histidine-containing dipeptides reduce central obesity and improve glycaemic outcomes: A systematic review and meta-analysis of randomized controlled trials
Supplemented groups had lower waist circumference (WMD -3.53 cm, 95% CI -5.65 to -1.41, p = 0.001) and lower HbA1c (WMD -0.76%, 95% CI -1.29 to -0.24, p = 0.004) than controls.
Meta-analysisHumansWith histidine-containing dipeptides (carnosine, anserine, beta-alanine studies pooled) - A Systematic Risk Assessment and Meta-Analysis on the Use of Oral beta-Alanine Supplementation
Paraesthesia was the only side effect reported, with an odds ratio of 8.9 (95% CrI 2.2 to 32.6) versus placebo.
Meta-analysisHumansWith beta-alanine (carnosine precursor) - beta-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis
Overall effect size was 0.18 (95% CI 0.08 to 0.28).
Meta-analysisHumansWith beta-alanine (carnosine precursor) - Systematic review and stratified meta-analysis of the efficacy of carnosine in animal models of ischemic stroke
The authors report that carnosine reduced infarct volume by 29.4% (95% CI 24.0% to 34.9%) across 29 comparisons.
Meta-analysisOther animals - Effects of beta-alanine supplementation on exercise performance: a meta-analysis
Beta-alanine produced a larger effect than placebo (median effect size 0.374 versus 0.108; P = 0.002).
Meta-analysisHumansWith beta-alanine (carnosine precursor)
Reviews in people
7 listed.
- N-acetylcarnosine (NAC) drops for age-related cataract
Two potentially eligible studies were found, one from Russia and one from the United States.
ReviewHumansWith N-acetylcarnosine (carnosine prodrug) eye drops - Optimizing human in vivo dosing and delivery of beta-alanine supplements for muscle carnosine synthesis
Across the eight studies that measured muscle carnosine, total grams of beta-alanine consumed correlated linearly with both relative and absolute increases in muscle carnosine; a dose-response study showed R2 of 0.921 over 8 weeks.
ReviewHumansWith beta-alanine (carnosine precursor) - Muscle carnosine metabolism and beta-alanine supplementation in relation to exercise and training
The authors report that carnosine is made in muscle from L-histidine and beta-alanine, with beta-alanine as the rate-limiting precursor, and that chronic oral beta-alanine can raise human muscle carnosine by up to 80%.
ReviewHumansWith beta-alanine (carnosine precursor) - Effect of beta-alanine supplementation on muscle carnosine concentrations and exercise performance
The review states that carnosine's imidazole ring (pKa 6.83) lets it buffer intracellular pH over the physiological range.
ReviewHumansWith beta-alanine (carnosine precursor) - Glycation, ageing and carnosine: are carnivorous diets beneficial?
The author proposes that carnivorous diets supply carnosine, a potential anti-glycating agent, whereas vegetarian diets lack it, and discusses possible effects of carnosine and related structures on protein carbonyl stress, AGE formation, secondary diabetic complications and age-related neuropathology.
ReviewHumans - Applicability of zinc complex of L-carnosine for medical use
Polaprezinc is described as the first oral drug in which zinc has an essential role.
ReviewHumansWith zinc (as polaprezinc) - Possible contribution of skeletal muscle buffers to enhanced anaerobic performance: a brief review
The authors propose that sprint-trained athletes may have a greater intracellular buffering capacity, and that higher glycolytic enzyme activity and a higher fast-twitch fibre proportion do not appear to account for their performance.
ReviewHumans
Reviews in animals
25 listed.
- Unveiling the hidden therapeutic potential of carnosine, a molecule with a multimodal mechanism of action: a position paper
The author describes carnosine as an endogenous dipeptide that is also sold as an over-the-counter food supplement, and lists its proposed mechanisms: neutralising reactive oxygen and nitrogen species, reducing pro-inflammatory mediators, inhibiting formation of abnormal proteins, and modulating macrophages and microglia.
ReviewOther animalsHumans - Carnosine, small but mighty: prospect of use as functional ingredient for functional food formulation
The authors describe carnosine as a dipeptide made from beta-alanine and L-histidine, found in high concentrations in brain, muscle and gastrointestinal tissue in all vertebrates.
ReviewHumansOther animals - Carnosine in health and disease
The authors state that carnosine was first found in skeletal muscle, where it is most concentrated, and that most research has focused on muscle and on whether supplementation improves athletic performance.
ReviewHumansOther animals - Carnosinases, their substrates and diseases
The authors describe carnosinases as Xaa-His dipeptidases found across all kingdoms of life.
ReviewHumansOther animals - Physiology and pathophysiology of carnosine
The authors describe carnosine as a dipeptide found in skeletal muscle and other excitable tissues, with methylated relatives (anserine, ophidine/balenine) in most animals other than humans.
ReviewHumansOther animals - Carnosine derivatives: new multifunctional drug-like molecules
The authors state that carnosine's many proposed therapeutic properties, mostly related to antioxidant and metal-chelating activity, are limited by the mechanisms governing its homeostasis, which has driven synthesis of derivatives; few have reached application.
ReviewOther animals - Carnosine: new concept for the function of an old molecule
The review traces how understanding of carnosine has changed, from a meat constituent of unknown purpose to a proposed regulator of intracellular signalling and gene expression.
ReviewHumansOther animals - Carnosine and cancer: a perspective
The authors state that many claimed therapeutic effects of carnosine have not been substantiated by rigorous experiment.
ReviewOther animals - Determinants of muscle carnosine content
Species is the main determinant of muscle carnosine: aerobically trained female vegetarian athletes (about 13 mmol/kg dry muscle) hold about a tenth of the level in trained thoroughbred horses.
ReviewHumansHorses - Role of L-carnosine in the control of blood glucose, blood pressure, thermogenesis, and lipolysis by autonomic nerves in rats: involvement of the circadian clock and histamine
Carnosine altered autonomic nerve activity and the associated physiological functions; these effects were abolished by histamine H1 or H3 antagonists and by lesions of the suprachiasmatic nucleus.
ReviewOther animals - Transforming dietary peptides in promising lead compounds: the case of bioavailable carnosine analogs
The authors review evidence that carnosine inhibits AGE and ALE formation in vitro and in some animal models by deactivating reactive carbonyl species.
ReviewOther animals - Carnosine and its possible roles in nutrition and health
The author reports that carnosine has shown anti-ageing activity at cellular and whole-animal levels.
ReviewOther animalsHumans - Carnosine and related dipeptides as quenchers of reactive carbonyl species: From structural studies to therapeutic perspectives
The authors propose that these dipeptides act by trapping reactive carbonyl species.
ReviewOther animals - Carnosine and homocarnosine, the forgotten, enigmatic peptides of the brain
In primary culture, synthesis and uptake of carnosine were shown to occur exclusively in glial cells, with uptake mediated by a high-affinity, energy-dependent dipeptide transporter later identified as PepT2.
ReviewOther animals - Carnosine and Carnosine-Related Antioxidants: A Review
The review describes carnosine as a skeletal-muscle dipeptide that scavenges reactive aldehydes from lipid peroxidation, buffers protons and chelates metals.
ReviewOther animals - Carnosine, the anti-ageing, anti-oxidant dipeptide, may react with protein carbonyl groups
The authors argue that the reported delay of senescence and rejuvenation of cultured human fibroblasts by carnosine is not fully explained by its antioxidant, radical-scavenging and metal-chelating actions.
ReviewOther animals - Role of histidine-related compounds as intracellular proton buffering constituents in vertebrate muscle
Histidine dipeptides such as carnosine and anserine, together with free histidine in some fish, are major non-bicarbonate buffers in muscle, and buffering capacity differs markedly between muscle types and species.
ReviewOther animals - Carnosine-related dipeptides in neurons and glia
The dipeptides are widely distributed in brain and spinal cord, in neurons and glia including mature astrocytes, oligodendrocytes, olfactory receptor neurons and putative migrating neuroblasts.
ReviewOther animals - Carnosine reacts with protein carbonyl groups: another possible role for the anti-ageing peptide?
The authors propose that, beyond its antioxidant and radical-scavenging actions, carnosine may take part directly in inactivating and disposing of aged proteins by reacting with their carbonyl groups.
ReviewOther animals - Cardiovascular effects of carnosine
The authors found carnosine dramatically increased contractility when perfused into isolated rat hearts.
ReviewOther animals - Carnosine-related dipeptides in the mammalian brain
High carnosine expression in olfactory receptor neurons led to the proposal of a neurotransmitter or modulator role in olfaction, which the authors state has not been fully demonstrated and does not explain the presence of the dipeptides in glial and ependymal cells.
ReviewOther animals - Carnosine, a protective, anti-ageing peptide?
The author summarises reports that carnosine extends the lifespan of cultured human fibroblasts, kills transformed cells, and protects cells against aldehydes and an amyloid peptide fragment.
ReviewOther animalsHumans - Endogenous skeletal muscle antioxidants
Carnosine and anserine concentrations vary widely by species and muscle type and are less affected by diet than alpha-tocopherol or glutathione peroxidase.
ReviewOther animals - Does carnosine possess direct antioxidant activity?
The author concludes that carnosine is a potent hydrophilic antioxidant with direct non-enzymatic action, characterised by high reactivity towards the hydroxyl radical, but that its known biological effects cannot be explained by antioxidant properties alone.
ReviewOther animals - The histidine-containing dipeptides, carnosine and anserine: distribution, properties and biological significance
The authors state that the biological significance of these muscle dipeptides is still open to question.
ReviewOther animalsHumans