Beta-Alanine

What it is

Beta-alanine is an amino acid sold as a sports supplement, most often as a powder [1]. Trials typically used 4 to 6.4 g per day for at least 4 weeks, sometimes up to 24 weeks [2][3].

How it might work

The body uses beta-alanine to build carnosine in muscle, and carnosine buffers the hydrogen ions produced during intense exercise, which may delay fatigue [2]. Supplementation reliably raises muscle carnosine: one trial saw a rise of about 9.4 mmol per kg of dry muscle after 28 days [4], and another saw gains grow from about 11.4 at week 4 to about 20.2 at week 24 of continuous use [3].

What the research says

The largest pooled analysis covered 40 double-blind, placebo-controlled studies with 1,461 participants and found a small overall benefit (effect size 0.18; 95% CI 0.08 to 0.28) [5]. Within efforts of 30 seconds to 10 minutes, tests of exercise capacity improved clearly (effect size 0.50), while race-style performance tests barely moved (effect size 0.11) [5]. A 2024 review of 18 studies in 331 trained young men found an effect size of 0.39, strongest for 4 to 10 minutes of maximal effort [2]. Pooled individual cycling data showed about 7.7 extra seconds to exhaustion alongside higher muscle carnosine [6].

Single trials agree: 14 trained cyclists lasted about 17.6 seconds longer to exhaustion after 4 weeks of 6.4 g per day [7]; 23 highly trained judo athletes landed more throws after 4 weeks of 6.4 g per day [8]; and 27 competitive runners improved time to exhaustion by 6.5% versus 1.4% with placebo after 28 days, with no change in aerobic capacity [9]. Women show the same pattern for time to exhaustion in 11 small trials, though the authors rate that evidence very low certainty [10].

The limits are equally clear: a 2026 meta-analysis of 17 trials found no effect on repeated sprint ability [11], matching null trials in road cyclists and elite kayakers [4][12]. Twenty trials with 492 participants found no change in body mass, fat or lean mass [13]. Effects around the aerobic-anaerobic threshold look small and uncertain [14].

Doses used in studies

Most performance trials used 4 to 6.4 g per day, split into smaller servings across the day, for at least 4 weeks [2][15]. A 24-week trial used 6.4 g per day of sustained-release beta-alanine [3]. Studies in older adults used 2.4 to 3.2 g per day for about 12 weeks [16]. One short trial used 12 g per day for 2 weeks and found no benefit [17]. These are study doses, not recommendations.

Safety and interactions

Skin tingling (paraesthesia) is the only reported side effect, much more common with beta-alanine than placebo, while dropout rates were similar to placebo [18]. Supplementation caused a small rise in blood alanine aminotransferase, but average levels stayed well within normal clinical ranges [18]. Human studies found no effect on muscle taurine or histidine levels [18]. No official upper limit was identified in the sources reviewed; trials used 2.4 to 6.4 g per day for up to 24 weeks without serious harms reported [18][3]. No data on interactions with medicines, or on use in pregnancy and breastfeeding, were found in the reviews read.

Caveats and open questions

Effects differ by exercise type: clearest for sustained efforts of 30 seconds to 10 minutes, absent for repeated sprints [5][11]. Evidence in women and older adults is still thin: 11 small trials in women with very low certainty ratings, and 5 small studies in older adults [10][16]. Time-trial benefits remain uncertain: one review found only small, imprecise effects around the aerobic-anaerobic threshold [14].