Scientific Opinion on the substantiation of health claims related to
branched-chain amino acids (BCAA) and growth or maintenance of muscle
mass (ID 442, 444, 445, 447, 448, 451, 1478), attenuation of the decline in
muscle power following exercise at high altitude (ID 443), faster recovery
from muscle fatigue after exercise (ID 447, 448, 684,1478), improvement of
cognitive function after exercise (ID 446), reduction in perceived exertion
during exercise (ID 450) and “healthy immune system” (ID 449) pursuant
to Article 13(1) of Regulation (EC) No 1924/2006[sup]1[/sup]
EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3
European Food Safety Authority (EFSA), Parma, Italy
Słowa kluczowe:
Branched-chain amino acids
cognitive function
health claims
muscle
physical performance
protein
1. Charakterystyka żywności / składnika
The food constituents that are the subjects of the health claims are proteinogenic branched-chain amino acids (BCAA), which are amino acids having aliphatic side-chains that are non-linear, i.e., leucine, isoleucine and valine. The content of BCAA in foods can be measured by established methods.
Leucine, isoleucine and valine are indispensable amino acids provided by mixed dietary protein intakes from different sources. A claim on protein and growth or maintenance of muscle mass has already been assessed with a favourable outcome (EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA), 2010).
BCAA can also be consumed as food supplements. Different mixtures are available in the market. From the references and conditions of use provided in relation to the health claims considered in this opinion, the Panel assumes that the food constituent under evaluation is BCAA consumed in addition to adequate protein intakes.
The Panel considers that the food constituent, branched chain amino acids, which is the subject of the health claims, is sufficiently characterised.
2. Znaczenie oświadczenia dla zdrowia człowieka
2.1. Wzrost lub utrzymanie masy mięśniowej (ID 442, 444, 445, 447, 448, 451, 1478)
The claimed effects are “reduces protein breakdown after exercise”, “increases protein synthesis”, “recovery/increased protein synthesis in skeletal muscle during recovery from sustained strength exercise” and “muscle metabolism”. The Panel assumes that the target population is the general population.
In the context of the proposed wordings, the Panel assumes that the claimed effect relates to the growth or maintenance of muscle mass by either decreasing muscle breakdown, increasing muscle
synthesis or both. Failure to increase muscle mass during growth and development, and the loss of muscle mass at any age, will reduce muscle strength and power.
The Panel considers that growth or maintenance of muscle mass is a beneficial physiological effect.
2.2. Tłumienie spadku siły mięśniowej następującego po wysiłku fizycznym na dużych wysokościach (ID 443)
The claimed effect is “attenuates the decline in power output following exercise at high altitude”. The Panel assumes that the target population is active individuals performing high altitude training.
Maintaining muscle power may be beneficial during every day life activities at high altitude, and is beneficial for athletic performance in disciplines where loss of muscle power reduces performance at high altitude.
The Panel considers that attenuation of the decline in muscle power following exercise at high altitude is a beneficial physiological effect.
2.3. Szybsza regeneracja mięśni po wysiłku fizycznym (ID 447, 448, 684, 1478)
The claimed effects are “muscle metabolism” and “promotes muscle recovery after exercise”. The Panel assumes that the target population is active individuals in the general population.
In the context of the proposed wordings and clarifications provided by Member States, the Panel assumes that the claimed effect refers to recovery from muscle fatigue after the performance of physical exercise.
Fatigue can be defined as the loss of peak force or power output. Therefore, muscle fatigue recovery can be defined as regaining maximal muscle strength or muscle power after strenuous exercise, which has induced muscle fatigue. Regaining muscle strength/power may be beneficial during every day life activities and it is beneficial for athletic performance in disciplines where loss of muscle strength and power reduce performance.
The Panel considers that faster recovery from muscle fatigue after exercise is a beneficial physiological effect.
2.4. Poprawa zdolności poznawczych po ćwiczeniach/treningu (ID 446)
The claimed effect is “improves mental performance after exercise”. The Panel assumes that the target population is active individuals in the general population.
In the context of the clarifications provided by Member States, the Panel assumes that the claimed effect relates to improving cognitive function after exercise. Cognitive function includes memory, attention (concentration), learning, intelligence and problem solving, which are well defined constructs and can be measured by validated psychometric cognitive tests.
The Panel considers that improvement of cognitive function after exercise is a beneficial physiological effect.
2.5. Zmniejszenie stopnia odczuwania wysiłku podczas ćwiczeń (ID 450)
The claimed effect is “BCAAs improve performance during sustained exercise”. The Panel assumes that the target population is active individuals in the general population.
In the context of the proposed wordings and clarifications provided by Member States, the Panel assumes that the claimed effect refers to a reduction in perceived exertion during exercise.
The Panel considers that a reduction in perceived exertion during exercise is a beneficial physiological effect.
2.6. Zdrowie układu odpornościowego (zmiana niektórych markerów odpowiedzi immunologicznej) (ID 449)
The claimed effect is “help maintain a healthy immune system”. The Panel assumes that the target population is the general population.
The claimed effect is not sufficiently defined and no more details were provided in the proposed wordings. The clarifications provided by Member States refer to the “improvement of some plasma markers of immune response”, and the references provided report on changes in a number of biochemical variables related to the immune system following the administration of BCAA. However, the Panel considers that the evidence provided does not establish that changes in these immune parameters are per se a beneficial physiological effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and a beneficial physiological effect related to a “healthy immune system”.
3. Naukowe uzasadnienia wpływu na zdrowie człowieka
3.1. Wzrost lub utrzymanie masy mięśniowej (ID 442, 444, 445, 447, 448, 451, 1478)
A number of references provided reported on human intervention studies which investigated the effects of BCAA mixtures on measures of physical capacity, physical performance, muscle soreness, muscle fatigue, plasma and muscle concentrations of BCAA, protein synthesis and/or protein breakdown in which changes in muscle mass were not measured. The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claimed effect.
Two human intervention studies, which aimed to investigate the effects of BCAA on surrogate measures of muscle mass (i.e. muscle cross-sectional area estimated from skin fold thickness and circumference measurements), were provided (Bigard et al., 1996; Schena et al., 1992).
The study by Bigard et al. (1996) tested the effect of BCAA supplement (BCAA, 7.8 g/d leucine, 3.4 g/d isoleucine and 11.2 g/d valine, corresponding to 35 %, 15 % and 50 % of total BCAA, respectively, 49 % energy from carbohydrate, 13 % from protein, 38 % from fat, n=11) versus a carbohydrate supplement (control, 98 % energy from carbohydrate, n=11) on surrogate measures of muscle mass in the arm in highly trained subjects who participated in six successive sessions of ski mountaineering (6-8 hr duration, altitude 2,500-4,100 m). The energy content of the total diet was controlled. The protein content in the diets including the supplements was 1.2 g per kg body weight per day in the control group and 1.44 g per kg body weight per day in the BCAA group. In the study by Schena et al. (1992) with a similar design, the effect of a BCAA supplement (BCAA, 7.8 g/d leucine, 3.4 g/d isoleucine and 11.2 g/d valine, corresponding to 35 %, 15 % and 50 % of total BCAA, 49 % energy from carbohydrate, 13 % from protein, 38 % from fat, n=4) versus a carbohydrate supplement (control, 98 % energy from carbohydrate, n=5) on surrogate measures of muscle mass in the arm and thigh was tested during altitude acclimatisation (21-day trekking). The Panel notes that the design of these small studies does not allow any conclusions to be drawn on the effects of BCAA independently of higher protein intakes and that direct comparisons between the intervention (BCAA) and control groups regarding the outcome variables were not reported. The Panel considers that no conclusions can be drawn from these studies for the scientific substantiation of the claimed effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and growth or maintenance of muscle mass over and above the well established role of protein on the claimed effect.
3.2. Tłumienie spadku siły mięśniowej następującego po wysiłku fizycznym na dużych wysokościach (ID 443)
The scientific evidence provided in the consolidated list on the effects of branched chain amino acids on attenuation of the decline in muscle power following exercise at high altitude consisted of 18 references of which 16 were not pertinent to the claimed effect either because muscle power was not reported or exercise was not performed at high altitude. The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claimed effect.
Two intervention studies investigated the effects of BCAA on muscle power during exercise performed at high altitude (Bigard et al., 1996; Schena et al., 1992). These studies have been described in detail in section 3.1.
In the study by Bigard et al. (1996), peak power output during an incremental bicycle exercise was tested, whereas in the study by Schena et al. (1992) lower limb muscle power estimated by repeated maximal jump during altitude acclimatisation (21-day trekking) was assessed. The Panel notes that the design of these small studies does not allow any conclusions to be drawn on the effects of BCAA independently of higher protein intakes and that direct comparisons between the intervention (BCAA) and control groups regarding the outcome variables were not reported. The Panel considers that no conclusions can be drawn from these studies for the scientific substantiation of the claimed effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and attenuation of the decline in muscle power following exercise at high altitude.
3.3. Szybsza regeneracja mięśni po wysiłku fizycznym (ID 447, 448, 684, 1478)
Most of the references provided in relation to this claim reported on intervention studies which did not assess recovery of maximal muscle strength or power after strenuous exercise (but rather other outcomes such as perceived exertion during exercise or measures of physical capacity, physical performance, muscle soreness, muscle fatigue, plasma and muscle concentrations of BCAA, protein synthesis and/or protein breakdown) or where the effect of a mixture of amino acids, and not only BCAA, was investigated, as in Sugita et al. (2003) and Ohtani et al. (2006). The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claimed effect.
The remaining six references consisted of one review (Blomstrand et al., 1996) and five intervention studies (Shimomura et al., 2006; Crowe et al., 2006; Watson et al., 2004; Bigard et al., 1996; Schena et al., 1992). Two of the intervention studies were performed at high altitude and have been described in section 3.2 (Bigard et al., 1996; Schena et al., 1992).
In a small randomised, controlled, double-blinded study by Crowe et al. (2006), 13 competitive outrigger canoeists were tested before and after 6 weeks daily supplementation containing either leucine (45 mg/kg body weight/day, n=6) or cornflour (45 mg/kg body weight/day, n=7). Before and after the intervention the following tests were performed: upper body 10 s power test and a row to exhaustion at 70–75 % maximal aerobic power. The Panel notes that a test of muscle fatigue recovery was not included as an outcome parameter, and that the study was not performed with the food constituents that are the subject of the health claim (e.g. a BCAA mixture). The Panel considers that no conclusions can be drawn from this study for the scientific substantiation of the claimed effect.
In a randomised double-blinded cross-over study by Watson et al. (2004) the effect of a sugar-free fruit drink containing 12 g/L BCAA (6 g/L leucine, 3 g/L valine, and 3 g/L isoleucine) supplementation was tested compared to placebo (sugar-free fruit drink). Eight glycogen-depleted men participated and ingested 250 mL (placebo or BCAA) at 30 min intervals, the last 2 h prior to
exercise, and 150 mL every 15 min throughout cycling to exhaustion in a warm environment (30 C).
BCAA ingestion had no effect on exercise capacity (placebo 104 27 min; BCAA 111 29 min, p=0.13). Because differences in muscle strength and power recovery between groups were not reported, the Panel considers that no conclusions can be drawn from this study for the scientific substantiation of the claimed effect.
In a randomised, controlled, blinded cross-over study 16 women and 14 men ingested a BCAA mixture (5 g, Ile:Leu:Val = 1:2.3:1.2), which also contained 1 g of green tea powder and 1.2 g of an energy-free sweetener, or a placebo solution containing the same ingredients as the BCAA solution, but substituting 5 g dextrin for the BCAAs (Shimomura et al., 2006). The solutions were ingested 15 min before a strenuous exercise protocol intended to induce muscle fatigue. Muscle fatigue was evaluated daily using a visual-analogue scale (self-reported) up to five days post-exercise. No significant differences in (self-reported) fatigue between the BCAA and placebo groups were observed. Because changes in objective measures of muscle fatigue recovery (e.g. differences in muscle strength and power recovery) between groups were not reported, the Panel considers that no conclusions can be drawn from this study for the scientific substantiation of the claimed effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and faster recovery from muscle fatigue after exercise.
3.4. Poprawa zdolności poznawczych po ćwiczeniach/treningu (ID 446)
A total of 21 references were provided to substantiate the claimed effect, including two textbooks, two narrative reviews and 17 human studies.
One textbook described the transport mechanisms of BCAA into the brain. The second textbook provided general information on brain nutrients. One narrative review and 11 human studies addressed the effect of BCAA consumption on muscle metabolism and physical performance. The second narrative review did not address the food constituent which is the subject of the health claims. Two human studies investigated the effect of BCAA consumption on immune parameters. The Panel considers that no conclusions can be drawn from these references for the scientific substantiation of the claimed effect.
A total of five human intervention studies addressed the effect of BCAA consumption on relevant endpoints for the claimed effect.
Two of the studies were randomised double-blind placebo-controlled trials where the effect of a BCAA drink on cognitive function, compared to a control drink, was assessed (Blomstrand et al., 1991a, b). In the first study, the subjects (n=16) received either a BCAA drink (50 % valine, 35 % leucine, 15 % isoleucine in a 5 % carbohydrate solution providing 7.5 g BCAA/ subject) or a placebo drink (5 % carbohydrate solution) during a 30 km cross-country race (Blomstrand et al., 1991a). In the second study, six female subjects were given either a 6 % carbohydrate drink containing BCAA (7.5 g/L, 40 % valine, 35 % leucine, 25 % isoleucine) or a 6 % carbohydrate solution (placebo) during two games of soccer (cross-over) (Blomstrand et al., 1991b). The Stroop Colour and Word Test (CWT) was used to assess the cognitive performance before and after physical exercise in both studies. The Panel notes that the designs of these small studies, where the treatment and control drinks were not isocaloric, limit the conclusions that can be drawn on the specific effect of BCAA, and that direct comparisons between the intervention (BCAA) and control groups regarding the outcome
variables were not reported. The Panel considers that no conclusions can be drawn from these studies for the scientific substantiation of the claimed effect.
In an article from Hassmen et al. (1994), the results of two studies on the effect of BCAA supplementation during a 30 km competitive run on post-run cognitive performance were reported. The studies involved 23 and 29 subjects, who were randomly assigned to an experimental group (receiving a BCAA drink (40 % valine, 35 % leucine, 25 % isoleucine in a 7 % carbohydrate solution), providing 5.3 g of BCAA/subject) or a placebo group (receiving a 7 % carbohydrate solution) respectively. The Stroop Colour and Word Test (CWT) or five paper-and-pencil tests were respectively used to assess the cognitive performance before and after physical exercise. The two-way ANOVA revealed no significant main effects of treatment compared to placebo in both studies. The Panel notes that the differences in energy content between the treatment and control drinks in these studies, which used a small number of subjects to evaluate multiple endpoints, greatly limits the conclusions that can be drawn for the scientific substantiation of the claimed effect.
In another randomised double-blind placebo-controlled cross-over trial, seven endurance-trained cyclists were given 150-200 mL of either a solution of BCAA (7 g/L of BCAA (40 % valine, 35 % leucine and 25 % isoleucine), lemon flavour, salts, citric acid and artificial sweetener; corresponding to 90 mg BCAA/kg body weight/subject) or flavoured water (placebo; containing lemon flavour, salts, citric acid and artificial sweetener in slightly different proportions), before and every 15 min during an 80 min exercise (60 min 70 % VO2max + 20 min maximal effort) (Blomstrand et al., 1997). The subjects were given the CWT after the end of the exercise, in order to assess their cognitive performance. The performance in the colour task of CWT was significantly improved in the treatment group compared to the placebo group (83.2 (74-97) versus 78.9 (62-97) p<0.05 for BCAA versus placebo; Wilcoxon's signed rank test was applied because of skewed distribution of data in this small sample). For the word and colour-word tasks, no difference was detected between the treatment and placebo groups. The Panel notes that the treatment and placebo drinks were not isocaloric and the use of a non-isocaloric control might explain the significant decrease in muscle glycogen observed in the control group compared with the treatment group. The Panel notes that the number of subjects recruited was small and that the difference in energy intake and glycogen utilisation between the treatment and placebo groups greatly limits the conclusions that can be drawn for the scientific substantiation of the claimed effect.
In weighing the evidence, the Panel noted that only one study using a small number of volunteers showed a significant effect of BCAA consumption compared to a non-isocaloric placebo on one of the cognitive endpoints measured and that two studies which compared the effect of BCAA-containing drinks to non-isocaloric placebo drinks did not show any significant effect of BCAA on the cognitive endpoints measured.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and improvement of cognitive function after exercise.
3.5. Zmniejszenie stopnia odczuwania wysiłku podczas ćwiczeń (ID 450)
Only one of the two references provided for the scientific substantiation of this claim addressed the effects of BCAA on perceived exertion during exercise (Blomstrand et al., 1997).
In a randomised double-blind placebo-controlled crossover intervention (Blomstrand et al., 1997), seven endurance-trained cyclists were given 150-200 mL of either a solution of BCAA (7 g/L of BCAA (40 % valine, 35 % leucine and 25 % isoleucine), corresponding to 90 mg BCAA/kg body weight) or flavoured water (placebo) before and every 15 min during an 80 min exercise (60 min 70 % VO2max + 20 min at maximal effort). Every 10 min during exercise the subjects rated their perceived exertion on the 15 degree (6 to 20) category scale developed and validated by Borg (1970).
The area under the curve for ratings of perceived exertion (RPE) during the 60 min period of exercise at fixed work rate was significantly lower in the intervention group compared to placebo (-7 %). No significant differences were observed between groups with respect to RPE during the last 20 min of exercise performed at maximal intensity. The Panel notes that the number of subjects recruited was small, and that the study was not adequately controlled for energy intake (i.e. energy content of the BCAA drink was higher than that of placebo), which could have accounted for the differences in RPE observed between groups, all of which greatly limit the conclusions that can be drawn from this study for the scientific substantiation of the claimed effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and a reduction in perceived exertion during exercise.
Wnioski
On the basis of the data presented, the Panel concludes that:
The food constituent, branched chain amino acids, which is the subject of the health claims, is sufficiently characterised.
Growth or maintenance of muscle mass (ID 442, 444, 445, 447, 448, 451, 1478)
The claimed effects are “reduces protein breakdown after exercise”, “increases protein synthesis”, “recovery/increased protein synthesis in skeletal muscle during recovery from sustained strength exercise” and “muscle metabolism”. The target population is assumed to be the general population. Growth or maintenance of muscle mass is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of BCAA and growth or maintenance of muscle mass over and above the well established role of protein on the claimed effect.
Attenuation of the decline in muscle power following exercise at high altitude (ID 443)
The claimed effect is “attenuates the decline in power output following exercise at high altitude”. The target population is assumed to be active individuals performing high altitude training. Attenuation of the decline in muscle power following exercise at high altitude is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of BCAA and attenuation of the decline in muscle power following exercise at high altitude.
Faster recovery from muscle fatigue after exercise (ID 447, 448, 684, 1478)
The claimed effects are “muscle metabolism” and “promotes muscle recovery after exercise”. The target population is assumed to be active individuals in the general population. Faster recovery from muscle fatigue after exercise is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of BCAA and faster recovery from muscle fatigue after exercise.
Improvement of cognitive function after exercise (ID 446)
The claimed effect is “improves mental performance after exercise”. The target population is assumed to be active individuals in the general population. Improvement of cognitive function after exercise is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of BCAA and improvement of cognitive function after exercise.
Reduction in perceived exertion during exercise (ID 450)
The claimed effect is “BCAAs improve performance during sustained exercise”. The target population is assumed to be active individuals in the general population. A reduction in perceived exertion during exercise is a beneficial physiological effect.
A cause and effect relationship has not been established between the consumption of BCAA and a reduction in perceived exertion during exercise.
“Healthy immune system” (ID 449)
The claimed effect is “help maintain a healthy immune system”. The target population is assumed to be the general population. The clarifications provided by Member States refer to the “improvement of some plasma markers of immune response” and the references provided report on changes in a number of biochemical variables related to the immune system following the administration of BCAA. However, the evidence provided does not establish that changes in these immune parameters are per se a beneficial physiological effect.
The Panel concludes that a cause and effect relationship has not been established between the consumption of BCAA and a beneficial physiological effect related to a “healthy immune system”.