Low efficiency of β-alanine supplementation to increase muscle carnosine: a retrospective analysis from a 4-week trial

Supplementation with β-alanine (BA) increases muscle carnosine content, although the amount of BA used for muscle carnosine loading has been suggested to be low. However, methodological issues may have underestimated the amount of BA used. The aim of this study was to determine the estimated amount of BA converted to muscle carnosine, using a retrospective analysis from a 4-week randomized controlled trial investigating the effects of BA supplementation on muscle carnosine content of the m. vastus lateralis. Twenty-five males (age 27±5 years, height 1.74±0.09 m, body mass 77.4±11.5 kg) were supplemented with 6.4 g·day-1 of BA (N=17) or placebo (PL; N=8) for 28 days. Pre- and postsupplementation participants provided a muscle biopsy subsequently analysed for carnosine content using HPLC. Data were analysed using mixed-models and Pearson’s correlations. Muscle carnosine content increased by +11.0±6.7 mmol·kg-1dm (P<0.0001) in BA, with no change in PL (P=0.99). The estimated amount of BA converted to muscle carnosine was 2.1±1.2% (Range: 0.5 to 4.5%) of the total dose ingested. Pearson’s correlations showed that pre-supplementation carnosine was correlated to post-supplementation carnosine in the BA group (r=0.65, r2=0.38, P=0.009), but not the absolute change in carnosine (r=-0.28, r2=0.08, P=0.28) or the amount of BA used (r=-0.31, r2=0.10, P=0.22). The estimated amount of ingested BA used for carnosine synthesis was extremely low following 4 weeks of BA supplementation at 6.4 g·day-1. Data suggest that very little of the BA ingested is used for muscle carnosine synthesis and highlights the potential for further work to optimise BA supplementation in humans.