Benefits
High-intensity exercise capacity in cycling tests
In a trial of 13 men on CarnoSyn and 12 matched placebo controls, 4 weeks raised total work done in a cycling test at 110% of maximum power by 13.0%, with a further 3.2% after 10 weeks, while the placebo group did not change. The gain followed the rise in muscle carnosine. The trial was small and run by researchers with NAI ties.
Muscle carnosine loading
CarnoSyn at 3.2 or 6.4 g a day for 4 weeks raised thigh muscle carnosine by about 42% and 64%, and 10 weeks raised it by about 80%. In adults aged 60 to 80, sustained-release tablets at 3.2 g a day for 12 weeks raised calf carnosine by 85.4% versus 7.2% on placebo. Carnosine is a marker, not a performance result.
Exercise capacity and fatigue threshold in adults over 55
Two small placebo-controlled trials found gains: 90 days of 2.4 g a day raised the cycling workload reached before muscle fatigue by 28.6% in a trial of 26 adults aged 55 to 92 (12 on beta-alanine), and 12 weeks of sustained-release tablets lengthened time to exhaustion in 18 adults aged 60 to 80. A 100-person trial found no difference from placebo in grip strength or sit-to-stand.
Power and combat task performance in soldiers
In two 4-week trials of 6 g a day of sustained-release tablets in elite combat soldiers, the CarnoSyn groups showed higher peak jump power, more shots on target and a faster 50 m casualty carry than placebo. Run times, sprints and, in the second trial, marksmanship did not differ. Each trial had about 20 soldiers.
Cognitive test scores in soldiers and older adults
In one trial of 18 soldiers, serial subtraction scores were better than placebo after 30 days, but a trial of 20 soldiers and a trial of 19 cyclists found no effect on cognitive tests. In 100 older adults, overall cognitive screening scores did not differ from placebo, though people with lower starting scores improved more.
Mechanism of action
Building muscle carnosine
Muscle makes carnosine from beta-alanine and histidine, and beta-alanine is the scarce ingredient. Taking it daily raises muscle carnosine over weeks, in both type I and type IIa fibers, which is why the trials ran for at least 4 weeks rather than testing single doses.
Acid buffering during hard efforts
Carnosine soaks up hydrogen ions inside muscle, slowing the fall in pH during intense exercise. This is the proposed reason the CarnoSyn trials found gains in efforts that end in fatigue, such as cycling to exhaustion, rather than in short single sprints.
Sustained-release delivery
SR CarnoSyn is a sustained-release tablet form. In a study of slow-release beta-alanine tablets whose brand was not named, the blood peak was lower and later than with a pure solution, total absorption was the same, less was lost in urine, and tingling did not differ from placebo. Tingling tracked blood levels, so a lower peak is the likely reason.
Clinical trials
Absorption and supplementation study: single doses of 10, 20 and 40 mg/kg of CarnoSyn (named in the abstract) or chicken broth, then 3.2 or 6.4 g a day of beta-alanine in 400 or 800 mg doses, or L-carnosine, for 4 weeks, with muscle biopsies; co-authored by John Wise, described in a later paper as a former NAI employee (Harris et al. 2006, Amino Acids)
Healthy adult volunteers; the abstract does not give the number per group.
Blood beta-alanine peaked and returned to baseline within 2 hours, with under 5% lost in urine. Four weeks raised muscle carnosine by 42.1% (3.2 g) and 64.2% (6.4 g). Plasma taurine rose without extra loss in urine. Muscle carnosine is a marker; no performance test was reported.
Placebo-controlled trial of CarnoSyn (named in the abstract) for 4 weeks, 8 participants continuing to 10 weeks, with muscle biopsies and a cycling capacity test at 110% of maximum power; funding not stated in the abstract; co-authors include Roger Harris, who later disclosed NAI research grants and NAI patents, and John Wise, later described as a former NAI employee (Hill et al. 2007, Amino Acids)
25 participants: 13 men on beta-alanine and 12 matched placebo controls.
Muscle carnosine rose 58.8% at 4 weeks and 80.1% at 10 weeks, with no rise on placebo, and muscle taurine did not change. Total work done rose 13.0% at 4 weeks and a further 3.2% at 10 weeks, while it did not change in the placebo group. Small groups, and only a subset in each group had muscle biopsies.
Double-blind randomized placebo-controlled trial: 800 mg CarnoSyn capsules three times a day versus microcrystalline cellulose for 90 days; NAI donated the CarnoSyn and placebo; Roger Harris is a co-author (Stout et al. 2008, J Int Soc Sports Nutr)
26 older adults (9 men, 17 women), average age 72.8; 12 on beta-alanine, 14 on placebo.
Physical working capacity at the fatigue threshold, a cycling workload measure, showed a group by time interaction (p = 0.007): it rose 28.6% on CarnoSyn and did not change on placebo. 67% of the CarnoSyn group improved versus 21.5% on placebo. No other outcomes were reported.
Double-blind randomized placebo-controlled trial: two 800 mg sustained-release CarnoSyn tablets twice a day versus maltodextrin for 12 weeks; NAI partly sponsored the study and supplied the tablets, with state research foundation support; John Wise is a former NAI employee and NAI consultant, and Roger Harris is a named inventor on NAI patents (del Favero et al. 2012, Amino Acids)
18 healthy adults aged 60 to 80: 12 on beta-alanine and 6 on placebo.
Calf muscle carnosine rose 85.4% versus 7.2% on placebo (p = 0.004). Time to exhaustion in a constant-load test rose 36.5% versus 8.6% (p = 0.05), and in an incremental test 12.2% versus 0.1% (p = 0.04). The carnosine rise correlated with the gains. Timed-stands, timed up-and-go and quality of life did not differ, and no side effects were reported. A very small placebo group.
Randomized placebo-controlled trial: sustained-release CarnoSyn tablets, 2 g (two tablets) three times a day, versus rice powder during advanced military training; CarnoSyn obtained from NAI, which the authors thank for supporting the study; the lead author later disclosed past NAI consulting (Hoffman et al. 2014, J Int Soc Sports Nutr)
20 soldiers from an elite combat unit, average age 20.
Peak jump power (p = 0.034), shots on target (8.2 versus 6.5, p = 0.012) and target engagement speed (p = 0.039) were better than placebo. The 4 km run (p = 0.597) and serial subtraction, a cognitive test (p = 0.844), did not differ. Four soldiers had isolated episodes of tingling, each after taking 2 to 3 doses at once.
Randomized placebo-controlled trial: sustained-release CarnoSyn tablets, 2 g (two tablets) three times a day, versus rice powder, with muscle and brain carnosine measured by magnetic resonance spectroscopy; CarnoSyn obtained from NAI, which the authors thank for support; the lead author later disclosed past NAI consulting (Hoffman et al. 2015, Amino Acids)
18 soldiers from an elite combat unit, average age 19.9.
Muscle carnosine rose more than on placebo (p = 0.048); brain carnosine did not change. The 50 m casualty carry (p = 0.044) and serial subtraction scores (p = 0.022) improved more than placebo. The 2.5 km run, 1 minute sprint, repeated sprints and marksmanship did not differ.
Double-blind randomized placebo-controlled trial: sustained-release beta-alanine tablets with meals, 2.4 g a day for 10 weeks; tablets provided by NAI, which also funded the research; the paper declares no conflict of interest, but the senior author disclosed in a separate 2023 review that he has previously consulted for NAI (Ostfeld et al. 2023, Nutrients)
100 older adults, average age 70.6; 79 completed (38 beta-alanine, 41 placebo).
The main cognitive screening score (MoCA) did not differ between groups (p = 0.19). In a subgroup with starting scores of 26 or less, MoCA improved more than placebo (interaction p = 0.042). Stroop test results, mood, anxiety, grip strength and sit-to-stand did not differ; depression scale scores fell on beta-alanine only. No adverse events were reported.
Placebo-controlled trial: 6.4 g a day of sustained-release CarnoSyn (named in the abstract) or maltodextrin for 24 weeks, with muscle biopsies at 0, 12 and 24 weeks and blood tests every 4 weeks; Roger Harris is a co-author (Saunders et al. 2020, Eur J Nutr)
25 healthy men, average age 27: 16 on beta-alanine and 9 on placebo.
Muscle taurine showed no time or group by time effect (values were lower overall in the placebo group). Kidney, liver and muscle blood markers showed no treatment, time or interaction effect, and no participant reported side effects over 24 weeks. A small trial in men only.