BCAAs: Are they worth the hype? Original paper

Given the importance of protein for exercise, branched chain amino acids (BCAAs; isoleucine, leucine, and valine), which contribute heavily to muscle synthesis, are commonly marketed by supplement companies as being able to provide benefits for resistance training performance, recovery, and body composition. Are they effective, or a waste of money?

This systematic review of 12 randomized controlled trials assessed the effects of BCAA supplementation on physical performance, muscle damage, and body composition.

Studies that met the following criteria were included:

• Assessed healthy people who were at least 18 years old, without chronic disease.
• Utilized BCAA supplementation in isolation compared to a matched control group.
• Assessed physical performance, muscle damage, or body composition as an outcome.

The sample size of the included studies ranged from 9 to 46, with an average of about 22 participants per study. The studies were published between 2008 to 2018, and study length varied from 1 day to 8 weeks. The average BCAA dose was 19.5 grams per day and was compared to either water, carbohydrate, artificial sweetener, or taurine (a non-essential amino acid). Ten of the studies recruited nonathlete participants, one recruited experienced runners, and one recruited soccer and rugby athletes.

Blood parameters: Eight studies assessed the effects of BCAA supplementation on blood parameters associated with muscle damage. Seven of them assessed creatine kinase (CK), three assessed lactate dehydrogenase, two assessed lactate, two assessed aldolase, and one article assessed myoglobin and interleukin 6 (IL-6).

Of the seven studies assessing CK, three reported a decrease in CK in the BCAA group compared to placebo following an exercise protocol designed to induce muscle damage (24, 72–96, and 48 hours after exercise in each study, respectively).^[4][11][12]

Of the three studies assessing lactate dehydrogenase and of the two studies assessing aldolase, one reported that both markers were lower 72 and 96 hours after an exercise protocol designed to induce muscle damage in a BCAA group, compared to placebo.^[11]

Of the two studies assessing lactate, one found that it was lower in the BCAA group than the placebo group immediately after a cycling exercise protocol.^[6]

The only study assessing myoglobin and IL-6 found no effect of BCAAs following an exercise protocol designed to induce muscle damage.^[2]

Body composition: Two studies evaluated participant body weight and lean mass. One of these studies found that BCAAs prevented body weight and lean mass loss during an 8-week calorie-restricted diet, compared to a control group consuming a carbohydrate supplement.^[9] Notably, the supplement used in the study demonstrating an effect of BCAAs also contained 1,000 mg of citrulline malate and 2,500 mg of L-glutamine. The placebo was a standard electrolyte sports beverage.

Performance:

• Repetitions performed: Three studies assessed repetitions performed, one of which reported that the BCAA group performed more squat exercise repetitions than a placebo group. The same study reported improvements in body composition.^[9]
• Total distance performed: Two studies assessed distanced performed, with no differences between groups in either study.
• Strength: Five studies assessed strength, one of which reported a greater increase in 3RM strength on squats and bench press in the BCAA group, compared to the placebo group. The same study reported improvements in body composition.^[9]
• Vertical jump: Three studies assessed vertical jump performance, none of which found an effect of BCAAs.
• Power: Three studies assessed power, none of which found an effect of BCAAs.
• Perceived exertion: Two studies assessed perceived exertion, one of which found an improvement at 75 and 90 minutes during a cycling protocol in a group consuming BCAAs, compared to a group consuming a carbohydrate-based electrolyte beverage.^[3]
• Muscle soreness: Six studies assessed muscle soreness and pain, four of which found a reduction in subjective muscle pain in groups consuming BCAAs, compared to a placebo.^{[2][4][7][11]} One reported an effect of BCAAs, as compared to an artificially-sweetened beverage 48 and 72 hours following an eccentric exercise protocol.^[2] A second study reported that BCAAs reduced muscle soreness 24 and 48 hours after an exercise protocol designed to induce muscle damage, compared to an artificially-sweetened beverage.^[4] A third study reported that consuming BCAAs with taurine reduced muscle soreness 48 hours after an exercise protocol designed to induce muscle damage as compared to a carbohydrate-based placebo,^[7] and in another study, consuming BCAAs before an eccentric bicep curl protocol reduced muscle soreness at 72 and 96 hours, as compared to a starch-based placebo.^[11]

While several studies demonstrated positive effects of BCAAs, several points must be considered:

• The background protein intake of the participants probably moderated the benefits of BCAAs. Since BCAAs are three essential amino acids, and therefore found in protein food sources, BCAAs might be less useful for individuals already consuming adequate protein. Of the eight studies reporting benefits of BCAAs, three did not utilize a dietary control or report participants’ total protein intake, only requiring that participants maintain their usual dietary habits,^{[4] [11][7]} and another study did not control participants’ dietary intakes nor provide information on their intake.^[6] In one study, participants maintained an overall protein intake of about 1.2 grams per kg of body weight per day (g/kg/day), which the authors noted was lower than the recommended range for resistance training individuals (1.4–2.0 g/kg/day).^[12] Another study utilized a calorie and carbohydrate-restricted diet, providing 35–40% of calories from protein.^[9] One study asked participants to maintain their habitual intake while assessing their calorie and macronutrient intake during the study, reporting that the BCAA group derived about 69% of total energy from carbohydrates, while information was not provided on fat or protein intake.^[3] One study provided all food to participants, providing 1.5 g/kg/day of protein to both BCAA and placebo groups.^[2]
• None of the studies compared BCAAs to another source of amino acids (e.g., a protein supplement or protein from food) except for one study utilizing both taurine and starch in comparator groups.^[7]
• Even if BCAAs were to provide a small benefit on markers of muscle damage or soreness, using BCAAs for this purpose might become redundant if training volume is managed appropriately to avoid excessive muscle damage in the first place.

Several other review papers have been published assessing the utility of BCAAs for resistance-trained individuals. Here are a few that were published recently:

A 2021 meta-analysis^[13] previously reviewed in Study Summaries assessing the effects of BCAAs on muscle soreness and markers of muscle damage found that BCAA supplementation reduced CK levels at less than 24 hours after exercise, as well as 24 and 48 hours after exercise, while improving muscle soreness at less than 24 hours only. However, the observed effects were small.

A 2021 narrative review^[14] assessing the effects of BCAAs on muscle strength and hypertrophy concluded that “... the proposed benefits of BCAA used in the marketing of supplements appears to be at odds with the overall state of the current literature, which does not support the efficacy of supplementation on muscle strength and hypertrophy."

A 2017 meta-analysis^[15] assessing the effects of BCAAs on muscle soreness and markers of muscle damage, reported that BCAAs reduces CK at less than 24 hours and 24 hours after exercise compared to a placebo, with no effects on lactate dehydrogenase or muscle soreness.

In a 2017 systematic review^[16] assessing the effects of BCAAs on markers of muscle damage, 6 of 11 studies reported a beneficial effect of BCAAs.