Carnosine
Carnosine (beta-alanyl-L-histidine), endogenous dipeptide sold as a supplement
Written by Aaron CuhaReviewed Sep 2026
Also known as: L-carnosine, beta-alanyl-L-histidine
An endogenous dipeptide sold as an anti-ageing supplement with no approval anywhere for any indication. Its largest randomised trial, 299 participants on 2 g a day, found no difference on any physical performance measure overall, with scattered significance only in age and sex subgroups. Serum carnosinase breaks most of an oral dose down before it reaches muscle, which is why the real evidence base sits with beta-alanine instead.
Overview
Carnosine is beta-alanyl-L-histidine, a dipeptide the body makes and concentrates in skeletal muscle and brain. It is sold widely as an anti-ageing and anti-glycation supplement, often alongside the prescription medicines on neighbouring pages of this archive and in similar language. It is not a medicine. There is no approval for carnosine as a drug in the United States, the United Kingdom, Australia or Canada.
One pharmacological fact dominates everything else here. Human serum contains carnosinase, an enzyme that hydrolyses carnosine to beta-alanine and histidine. Most of an oral dose is broken down before it can reach muscle intact. The rate-limiting step for building muscle carnosine is the availability of beta-alanine, not of carnosine, which is why the substantial exercise literature is about beta-alanine and not about the dipeptide people actually buy.
The largest randomised trial of carnosine itself is instructive and is frequently misreported. 299 participants took 2 g a day or placebo, with hand grip strength, bilateral calf raise, a two-minute step test and gait speed measured at baseline, around six weeks and around twelve weeks. There was no significant difference on any measure overall. What the paper reports is a significant increase in calf raises at visit 3 in participants under 40 only, and a significant increase in step count at visit 4 in males over 40 only. Four measures, two timepoints and multiple subgroups produce a lot of opportunities for a P value below 0.05, and the authors themselves note the benefits appeared to be limited to males.
The precursor evidence is better characterised and smaller than the marketing implies. A meta-analysis of 40 studies and 1461 participants found an overall beta-alanine effect size of 0.18, which is small, concentrated in exercise lasting between about half a minute and ten minutes, and larger for exercise capacity than for performance.
Mechanism of action
Carnosine acts inside cells as a pH buffer in the physiological range, which is why it is concentrated in skeletal muscle where anaerobic work generates protons, and as a scavenger of reactive carbonyl species and aldehydes, which is the basis of the anti-glycation claims made for it. It also chelates transition metals. The practical problem is delivery, not mechanism: circulating carnosinase hydrolyses oral carnosine into beta-alanine and histidine, and muscle then resynthesises carnosine from those components with beta-alanine as the rate-limiting substrate. The consequence is that supplementing beta-alanine raises muscle carnosine more efficiently than supplementing carnosine does.
Human evidence
One large randomised trial of carnosine itself that was null on every prespecified measure and positive only within age and sex subgroups, plus a much larger literature on its precursor beta-alanine showing a small effect confined to a narrow exercise window.
- Carnosine, 299 participants, 2 g a day, 12 weeks: no significant difference on hand grip strength, calf raises, two-minute step test or gait speed overall.
- The only significant results were in subgroups: calf raises in the under-40s at one visit, step count in males over 40 at another.
- Beta-alanine meta-analysis, 1461 participants: overall effect size 0.18, small by any convention.
- Within exercise lasting 0.5 to 10 minutes, beta-alanine improved capacity (effect size 0.4998) but not performance (0.1078, confidence interval crossing zero).
- Total beta-alanine dose did not moderate the effect, which argues against a simple more-is-better reading.
What this does not tell you: A 299-person trial reporting scattered significance across four measures, two timepoints and several subgroups has a multiplicity problem, and it should not be cited as a demonstration that carnosine works. The beta-alanine evidence, which is far stronger, is evidence about beta-alanine: it supports taking the precursor for short-duration exercise capacity, and it says nothing about ageing, glycation, cognition or longevity. No trial has tested carnosine against any hard clinical outcome. Nothing in this record supports the anti-ageing positioning under which it is mostly sold.
Reading the research record
Carnosine is included in a batch of licensed medicines on purpose, because it is sold in the same places and in the same register as several of them while sitting in a completely different evidence category.
Three separate things travel under the carnosine name and are routinely conflated. The first is carnosine the supplement, whose best trial was null overall. The second is beta-alanine, the precursor, which is what the exercise science literature is actually about and which produces a small effect in a narrow duration window. The third is zinc-L-carnosine, also called polaprezinc, a chelate that is an approved prescription drug for gastric ulcer in Japan and has its own randomised evidence in mucosal protection. A Japanese drug approval for the chelate is not a regulatory endorsement of the dipeptide, and a meta-analysis of beta-alanine is not evidence for the dipeptide either.
The glycation story deserves its own note. Carnosine scavenges reactive carbonyls in vitro, and that is genuinely interesting chemistry. It is the basis for most of the anti-ageing marketing, and no human trial has shown that oral carnosine reduces advanced glycation end products in tissue, slows any ageing marker, or changes any clinical outcome. The distance between an in vitro chemical property and an anti-ageing claim is the entire subject here.
The evidence, charted
Fig. 1 · evidence composition
2of 3 citations (67%) are in people
Counted from the citation list on this page. The Human count is the same number shown in the badge at the top. Both understate any literature larger than the sources we cite.
Fig. 2 · evidence over time
Citations here span just two years, 2017 and 2026.
Too few distinct publication years on this page to plot as a timeline.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four jurisdictions shown. A jurisdiction's classification is a regulatory fact, not a verdict on the science; see Legal status below for the full text and any notes.
Key studies & citations
- Human2026
Effects of carnosine supplementation on physical endurance: a placebo-controlled randomized clinical trial
299 participants randomised to placebo or 2 g a day of carnosine, with hand grip strength, bilateral calf raise, two-minute step test and gait speed measured at baseline and at roughly 6 and 12 weeks. Results were subgroup-only: a significant increase in calf raises at visit 3 in participants under 40 (P equal to 0.018), and a significant increase in step count at visit 4 in males over 40 (P equal to 0.010). No significant differences were observed on any other physical performance measure, and the authors state the benefits appeared to be limited to males.
Journal of the International Society of Sports Nutrition - Review2017
beta-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis
40 studies, 65 exercise protocols, 70 exercise measures and 1461 participants. Overall effect size 0.18 (95 percent CI 0.08 to 0.28), which is small. Exercise duration moderated the effect (P equal to 0.004): within the 0.5 to 10 minute window the effect size was 0.4998 (95 percent CI 0.246 to 0.753) for exercise capacity but 0.1078 (95 percent CI minus 0.201 to 0.416) for exercise performance, and that second interval crosses zero. Total beta-alanine ingested did not moderate the effect (P equal to 0.438), nor did training status (P equal to 0.559).
British Journal of Sports Medicine - Human2026
Zinc-L-Carnosine (Polaprezinc) in managing infant regurgitation: a two-center randomized controlled trial
Sixty infants aged 4 weeks to 7 months with persistent regurgitation randomised to a zinc-L-carnosine liquid or thickened formula for 8 weeks, with a reflux questionnaire score as the primary outcome. Single-blind and designed as a non-inferiority study against thickened formula rather than against placebo. Included to mark the boundary: this is evidence about the zinc chelate in infants, not about carnosine as an anti-ageing supplement in adults.
Frontiers in Pediatrics
Frequently asked questions
Does carnosine do anything for ageing?
No human trial has shown that it does. The claims rest on in vitro carbonyl scavenging and anti-glycation chemistry. Its largest randomised trial measured physical function in 299 people and found no difference on any measure overall, with significance appearing only inside age and sex subgroups.
Should I take carnosine or beta-alanine?
If the goal is raising muscle carnosine, beta-alanine is the better-supported route. Serum carnosinase hydrolyses most oral carnosine before it reaches muscle, and beta-alanine is the rate-limiting precursor. The trade-off is that beta-alanine causes paraesthesia, a harmless but unpleasant tingling, which is dose-limiting for many people and does not appear in effect-size tables.
How big is the beta-alanine effect?
Small. A meta-analysis of 40 studies and 1461 participants found an overall effect size of 0.18. It is concentrated in exercise lasting roughly half a minute to ten minutes, and even there it improved exercise capacity more clearly than performance, with the performance confidence interval crossing zero.
Is zinc-L-carnosine the same thing?
No. Zinc-L-carnosine, or polaprezinc, is a zinc and carnosine chelate that adheres to damaged mucosa and releases zinc locally. It is an approved prescription drug for gastric ulcer in Japan and has its own randomised evidence in mucosal protection. Its approval says nothing about carnosine taken on its own for ageing.
Is carnosine approved for anything?
Not as carnosine. It is sold as a dietary supplement in the United States, a food supplement in the United Kingdom, a complementary medicine in Australia and a natural health product in Canada. None of those categories requires proof of efficacy, and none permits a claim to treat or prevent disease.