Strongest evidence
The only outcome with moderate evidence strength is increased carnosine levels. All 3 studies reported beneficial effects, with the most robust trial showing a large increase (+2.82 mmol/kg wet weight, p < 0.001) in COPD patients at 3.2 g/day over 84 days. Effects typically require 8–12 weeks of supplementation. This outcome also carries the caveat of a small evidence base and potential publication bias.
Mixed or weaker evidence
Six outcomes carry low or very low evidence strength. Improved physical performance (4 studies) shows mixed results: 2 small beneficial effects and 2 neutral. Reduced heart rate (5 studies) and reduced body fat mass (3 studies) are consistently neutral. Reduced lactate levels (3 studies) had 1 beneficial but 2 neutral results, with conflicting directionality. Reduced body mass (3 studies) and reduced rating of perceived exertion (3 studies) are uniformly neutral with no statistically significant findings.
Effective dose patterns
For increased carnosine levels, the effective dose is 3.2 g/day over at least 8 weeks. For physical performance and RPE, higher doses of 6.4 g/day are more commonly used, but results are inconsistent. Lactate studies used very high doses (20 g/day or 155 g cumulative over 7 days) with no clear benefit. Body composition outcomes show no effect regardless of dose.
Population insights
Most studies were conducted in athletic populations, including combat athletes, military personnel, cyclists, and basketball players. The strongest evidence for carnosine elevation comes from a COPD patient population, broadening the relevance beyond athletes. Elderly or deficient populations were not specifically studied in these syntheses.
Notable caveats
All syntheses are based on small evidence bases (3–5 studies each). Many studies did not reach statistical significance even when the direction was beneficial. Publication bias is a concern, particularly for the carnosine outcome. Study durations were often short (7–28 days), which may be insufficient for beta-alanine's effects to manifest fully. Dosing protocols varied widely, limiting cross-study comparability.