Is research on beta-alanine still in beta?

Muscle fatigue^[1] is a decline in maximal muscular force or power capacity. A reduction in muscular force can cause compensation through adoption of new movements or activation of other muscle groups. This can influence performance and predispose an individual to injury, which is why athletes and coaches are very calculated^[2] in scheduling their stages of training. Training and doing so at intensities beyond your comfort zone will almost always be the most efficient way to increase your overall resilience to muscle fatigue^[3], which is partially driven by acute intracellular and extracellular acidosis.

Muscular acidosis^[4] is a result of glycolysis, triggered by high-intensity exercise, which creates an acidic environment from metabolites of hasty glucose breakdown. Some of these metabolites, particularly protons (H+) and lactate ions, can impair steps^[5] of muscle contraction and glycolytic enzyme function (responsible for glucose breakdown). While the body has its own buffer system^[6] consisting of bicarbonate (primarily extracellular) and phosphates, proteins, and amino acids (primarily intracellular) to maintain blood pH levels within physiological range, their involvement in muscle is limited^[7].

Carnosine^[8] is a small protein made up of two amino acids, histidine and beta-alanine (BA), that mainly maintains acid-base balance within muscle. Higher carnosine concentrations have been significantly correlated with greater power output^[9], attributed to an increased buffering capacity, or the ability to reduce changes in pH. Don’t go buying carnosine supplements just yet, though — carnosine cannot be taken up well from the bloodstream^[10]. The synthesis of carnosine depends on the availability of BA, a modified version of the nonessential amino acid alanine, that can be obtained from the diet via consumption of white or red meat and can also be produced in the liver from alanine.

BA supplementation has demonstrated the potential to alleviate muscular fatigue^[11] and improve performance^[12] by increasing muscle carnosine levels that improve muscle buffering capacity, as shown in Figure 1. However, supplementation has resulted in conflicting results, with studies varying in dosage, duration, and participant population. Some aspects of BA metabolism are still being investigated, such as whether its entry into cells can be affected by similarly structured compounds (taurine, glycine, GABA) competing for the same transporter^[5], and vice-versa. In the study under review, researchers decided to review the existing literature on BA and its relationship with muscle fatigue and physical performance.

Muscle fatigue during exercise is the result of an accumulation of lactate and hydrogen ions produced from the breakdown of glucose when oxygen supply is limited, leading to muscular acidosis that contributes to impaired muscular contraction and energy metabolism. The main buffering agent in muscle tissue is carnosine, and beta-alanine supplementation has been shown to increase muscular carnosine concentrations and reduce muscle fatigue. The study under review is a systematic review of existing interventions with different dosages, durations, and populations to resolve conflicting results regarding the influence of beta-alanine supplementation on muscle fatigue and performance.