Is Branched-Chain Amino Acids Supplementation an Efficient Nutritional Strategy to Alleviate Skeletal Muscle Damage? A Systematic Review

Abstract

Amino acids and more precisely, branched-chain amino acids (BCAAs), are usually consumed as nutritional supplements by many athletes and people involved in regular and moderate physical activities regardless of their practice level. BCAAs have been initially shown to increase muscle mass and have also been implicated in the limitation of structural and metabolic alterations associated with exercise damage. This systematic review provides a comprehensive analysis of the literature regarding the beneficial effects of BCAAs supplementation within the context of exercise-induced muscle damage or muscle injury. The potential benefit of a BCAAs supplementation was also analyzed according to the supplementation strategy—amount of BCAAs, frequency and duration of the supplementation—and the extent of muscle damage. The review protocol was registered prospectively with Prospective Register for Systematic Reviews (registration number CRD42017073006) and followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Literature search was performed from the date of commencement until August 2017 using four online databases (Medline, Cochrane library, Web of science and ScienceDirect). Original research articles: (i) written in English; (ii) describing experiments performed in Humans who received at least one oral BCAAs supplementation composed of leucine, isoleucine and valine mixture only as a nutritional strategy and (iii) reporting a follow-up of at least one day after exercise-induced muscle damage, were included in the systematic review analysis. Quality assessment was undertaken independently using the Quality Criteria Checklist for Primary Research. Changes in indirect markers of muscle damage were considered as primary outcome measures. Secondary outcome measures were the extent of change in indirect markers of muscle damage. In total, 11 studies were included in the analysis. A high heterogeneity was found regarding the different outcomes of these studies. The risk of bias was moderate considering the quality ratings were positive for six and neutral for three. Although a small number of studies were included, BCAAs supplementation can be efficacious on outcomes of exercise-induced muscle damage, as long as the extent of muscle damage was low-to-moderate, the supplementation strategy combined a high daily BCAAs intake (>200 mg kg−1 day−1) for a long period of time (>10 days); it was especially effective if taken prior to the damaging exercise.

Ergogenic Effect of BCAAs and L-Alanine Supplementation: Proof-of-Concept Study in a Murine Model of Physiological Exercise

“…In particular, a clear reduction in CK release was detected in plasma samples of treated mice, which was particularly evident in mixtures containing lower ALA concentrations. Interestingly, the most remarkable decrease of LDH plasma level was observed in plasma from mice treated with mix 2, suggesting a further protective action of this formulation on structural integrity and metabolism of skeletal muscle during long-lasting exercise [11,29].…”

“…Therefore, BCAAs are recognized as potentially helpful dietary supplements to support skeletal muscle anabolism, particularly for athletes and fitness enthusiasts, as well as for elderly people to contrast age-related sarcopenia [3,10,11]. Focusing on physical activity, it is well-known that exercise promotes the oxidation of BCAAs under the control of energetic sensor AMP-activated protein kinase (AMPK) [2,12], and evidence suggests that the branched-chain alpha-keto acid dehydrogenase complex (BCKD)-at the second step of BCAAs catabolism-is activated during exercise by low ATP levels [3,13].…”

“…Independent studies in trained human subjects or exercised rodent models have shown that oral supplementation with BCAAs (or BCAAs-enriched mixtures) before and/or after exercise at variable doses (ranging from 77 mg/kg to 3 g/kg) promote protein synthesis, reduced muscle protein breakdown, as well as exercise-induced damage and fatigue [11,[14][15][16][17][18]. The preferred ratio for L-Leucine, L-Isoleucine, and L-Valine administration is 2:1:1 [11,[14][15][16][17][18], since BCAAs are quite safe if provided in similar proportions to those of mammal body protein [15]. Furthermore, the administration of leucine alone can ultimately lead to depletion of isoleucine and valine, since it activates the oxidation of all BCAAs [19].…”

“…It has been proposed that the supplement with the three BCAAs together, although preferred, could limit leucine effects due to the competition between these AAs for transport into muscle fibers [19]. Moreover, supplements with BCAAs alone may not effectively control muscle protein turnover, due to limited availability of other EAAs [3,11,19]. This hypothesis suggests that it would be preferable to combine BCAAs with other AAs, especially those involved in BCAAs metabolism.…”

Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake

“…According to a recent systematic review, a high (>200 mg/kg/day) and long-term (>10 days) daily supplementation of BCAA (including leucine, valine) could contribute in outcomes of low to moderate exercise-induced muscle damage, especially if consumed prior to the damaging exercise in healthy subjects [57]. Findings in elderly people showed that it is important to preserve a high proportion of leucine in an essential amino acid mixture, in order to reverse the suboptimal muscle protein synthesis-though this did not apply to younger subjects [58].…”