Carnosine and its precursor beta-alanine increase muscle strength, and have recently become extremely popular as dietary supplements in competitive sports.
Researchers at University of Bergen, Norway, have recently discovered an enzyme that forms beta-alanine from the common amino acid aspartic acid.
“This contrasts conventional wisdom that most beta-alanine is generated by degradation of nitrogen bases, such as uracil,” says senior author of the study, Professor Jan Haavik.
A new animal model
The researchers discovered the GADL1 enzyme 10 years ago, but have had difficulties determining the function of the enzyme.
To explore the function they studied a new mouse model lacking this enzyme. The picture is now a lot clearer.
“Mice lacking the enzyme, termed GADL1, had decreased levels of carnosine peptides in all tissues examined.
The reduction was most pronounced in the olfactory bulb (70-80 % reduction), a brain structure involved in sense of smell, but also affected in neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease.”
The reduction of carnosine was accompanied by a three-fold increase in the content ofglutathione reductase (GSR), an enzyme involved in antioxidant defense.
“In humans it has been found that genetic variants in GADL1 have been associated with many different traits, including muscle strength, subjective well-being and kidney function.
The new study shows that these genetic associations may be due different capacities for formation of beta-alanine and carnosine peptides.”
“The new animal model will also be useful to investigate the role of carnosine peptides in protection against age related diseases, such as cancer, cardiovascular and neurodegenerative diseases,” says Haavik.
During moderate to high-intensity exercise, hydrogen ions (H+) begin to accumulate leading to a drop in intramuscular pH and ultimately influencing muscle performance .
The greater the reliance on glycolysis as the primary energy system (as seen with high-intensity exercise), the greater production of lactic acid and H+, thus leading to further decreases in intramuscular pH.
This decrease in intramuscular pH has been suggested to be linked to fatigue-induced increases in muscle activation and electromyographic (EMG) amplitude [2,3].
Thus, if the intramuscular pH decline can be prevented or delayed, the fatigue induced EMG increase may also be delayed .
Beta-alanine (β-ALA) supplementation has been shown to increase muscle carnosine levels, which can act as a buffer to reduce the acidity in the active muscles during high-intensity exercise [5-7].
β-ALA supplementation has been shown to have beneficial effects on exercise performance variables such as cycling capacity , ventilatory threshold, and time to exhaustion .
For this reason β-ALA has become a widely used nutritional supplement for improving high-intensity exercise performance [4-6,9,10].
Creatine monohydrate supplementation has also been shown to have ergogenic effects by increasing the availability of phosphocreatine (PCr), total creatine concentrations in the muscle, high intensity exercise performance, and training adaptations .
For this reason, several studies have assessed whether co-ingesting β-ALA with creatine may have synergist and/or additive effects on exercise capacity and/or training adaptations [4,10,12].
The purpose of this article is to review the theoretical rationale and available scientific evidence assessing the potential ergogenic value of supplementing the diet with β-ALA with or without creatine. In addition, to discuss areas that future research should address.
This was accomplished by conducting a thorough review of the published literature related to the physiological effects of carnosine and the role of β-ALA and creatine supplementation on carnosine levels, creatine levels, and exercise performance.
Carnosine (β-alanyl-L-histidine) is a naturally-occurring histidine-containing compound found in many animal tissues, including skeletal muscle, which is the most abundant source.
Carnosine is a multifunctional dipeptide with many roles including buffering [13,14], fighting free radicals [15,16], enzyme regulation  and sarcoplasmic reticulum calcium (Ca2+) regulation [18,19].
Carnosine is broken down in the body by carnosinase, which is found in most tissues except skeletal muscle, partially explaining why carnosine concentrations are highest in this tissue . Figure 1 shows the chemical structure of carnosine.
Carnosine in human skeletal muscle generally ranges between 5-10 mM wet weight or 15–40 mmol/kg dry weight . Concentrations differ among animal species, in part due to the differences in muscle mass .
For example, horses have been reported to have higher carnosine concentrations than greyhound dogs . Carnosine levels are typically higher in fast-twitch muscle fibers compared to slow-twitch, which corresponds to the observation that animals exposed to frequent sprints, explosive flight behaviors and prolonged hypoxic dives have higher initial carnosine concentrations [5,21,22].
Human athletes involved in anaerobic sports such as sprinters [23,24] and bodybuilders  have also been found to have higher intramuscular concentrations of carnosine.
Exercise training has been reported to increase resting muscle carnosine concentrations in these athlete types. For example, Gardner and colleagues  reported that exercise training increased the plasma carnosinase activity and decreased carnosine excretion leading to greater muscle carnosine concentrations .
Moreover, Suzuki and colleagues  examined the effects of sprint training on muscle carnosine concentrations. Six male subjects performed sprint training twice a week for a total of 16 training sessions.
Each session involved either single (for weeks one and two) or a double (for weeks three through eight) bout of 30 seconds of maximal sprinting on a cycle ergometer with 20 minutes of rest between sprints on the double bout days.
Muscle samples were collected from the vastus lateralis one week before training and again two days following the training protocol. Results revealed that muscle carnosine content and mean power output significantly increased after the eight weeks of training .
Tallon and coworkers  suggested the greater muscle carnosine content in bodybuilders may be due to the chronic exposure to lower pH environments due to their training, differences in their diet such as increased protein intake where carnosine can be found, supplementation use, and/or possible anabolic androgenic steroid use .
Carnosine was first discovered as an intracellular pH buffer in 1953 by Severin and colleagues  using frog muscle tissue.
Subsequent studies examining this relationship in human muscle tissue followed thereafter [13,14,29-32]. When skeletal muscles are involved in moderate to intense exercise, there is typically a generation of lactic acid and subsequent dissociation into lactate and H+, which can alter the pH levels.
It had previously been reported that the majority of protons produced during exercise in the blood were buffered by the bicarbonate buffering system .
The pKa of this system is 6.1, which is less than that of carnosine (pKa of 6.83), and thus a greater pH change is needed to elicit benefits from this system.
Since the pKa of carnosine is closer to the physiological pH, it is likely that this is utilized sooner as a buffer during high-intensity exercise . The imidazole group on the histidine containing molecules, such as carnosine, makes it especially effective as a buffer.
This group has a pKa value close to that of the intracellular pH, therefore one of the nitrogens from the imidazole ring can be used to accept a proton .
Early studies examined the role of carnosine in animal models. One study, utilizing chromatography methodology to analyze rabbit and pigeon muscle samples, reported muscle dipeptides (mainly carnosine and anserine) accounted for approximately 40% of the pH buffering capability in skeletal muscle .
Later, Bump and colleagues  examined the carnosine concentrations in different breeds of horses.
They compared quarter horses (QH), thoroughbreds (TB) and standardbreds (SB) in order to correlate buffering capabilities of the muscle to fiber type composition. The QH demonstrated less slow-twitch muscle fibers, greater fast-twitch glycolytic fibers, and fewer fast-twitch oxidative muscle fibers compared to the other horses.
Results showed QH had significantly greater amounts of carnosine in their muscle.
The researchers reported a positive correlation between carnosine concentrations and fast-twitch glycolytic fibers and a negative correlation between carnosine and fast- twitch oxidative fibers.
The investigators inferred that intramuscular carnosine acted as an intracellular buffer, although this was not directly measured. A later study conducted by Sewell and associates  specifically examined the buffering capability of carnosine in different fiber types of horses.
These researchers found that carnosine contributed about 20% of the buffering in type I fibers and up to 46% in Type IIb fibers.
These findings are consistent with the findings that less lactic acid is accumulated in Type I fibers due to the lower intensity muscle activity involved with this fiber type.
An early study by Kraemer and associates of humans utilizing carnosine supplementation  reported no effect on the acid-base status or exercise performance using four subsequent 30 second Wingate tests with only two minutes of rest between exercise bouts.
In this regard, the researchers evaluated ten trained and ten untrained males who consumed a total of 15 capsules of a supplement containing 1000 mg dibasic sodium phosphate, 204 mg potassium bicarbonate and 12.5 mg L- carnosine over a 3.5 day period.
Placebo capsules were matched in sodium and potassium content. Blood samples were taken at baseline prior to any exercise, immediately after each Wingate test, and at three minutes after all exercise was completed.
Though intramuscular carnosine levels were not measured, the authors suggested that the amount of carnosine provided to subjects (about 185 mg) may have been too low to have an impact on intramuscular carnosine levels [26,38,39] particularly since previous animal studies had shown increases following a daily dose between 50-200 mg/kg of body weight [38,40].
Human studies have shown that lowered pH levels can also negatively affect the excitation- contraction coupling in the skeletal muscle [38,41]. The buffer efficacy in human muscle was examined by calculating the buffering ability over the physiological pH range of 7.1–6.5.
This study involved 50 healthy active individuals who underwent a muscle biopsy from the lateral portion of the quadriceps femoris muscle.
Anserine and carnosine were analyzed in neutralized perchloric acid extracts using high performance liquid chromatography (HPLC) methods.
The Henderson-Hasselbach equation was then used to indirectly calculate the buffer contribution across the pH range of 7.1 to 6.5. It was estimated that carnosine was able to buffer between 2.4 and 10.1 mmol H+·kg-1 dry mass, which corresponded to about 7% of the total muscle buffering .
Therefore, these results indicated that carnosine played a minimal role in buffering pH.
Suzuki and coworkers  examined the effects of the non-bicarbonate buffers carnosine and anserine.
They had eight active males supplement with either a placebo or chicken breast extract (CBEX) soup that contained 1.5 g carnosine and anserine. Subjects then performed ten sets of five second maximal cycle sprints at 7.5% of their body weight as resistance.
Blood samples were collected at rest, one minute before exercise, after each exercise set, and immediately after the intervals to measure blood-gas parameters, blood lactate and concentrations of carnosine and anserine.
The researchers found that supplementing the diet with CBEX delayed the decrease in bicarbonate during intense exercise, but did not improve performance. These results support the initial use of carnosine as a buffer instead of the bicarbonate system .
Early studies with carnosine supplementation noted plasma carnosine levels failed to elevate due to the high activity of carnosinase .
The researchers were able to measure only 14% of the ingested carnosine in urine suggesting this was due to absorption in the gastrointestinal tract .
Later, research pointed towards supplementing with β-ALA and L-histidine instead to raise carnosine levels since these are the precursors to carnosine. Dunnett and Harris  discovered that β-ALA was able to increase carnosine in muscle tissue.
In their study, they supplemented horses with both β-ALA and L- histidine and found β-ALA to have an additive response suggested to be due to the increase β-amino acid transport across the gastrointestinal tract.
This was not observed for L-histidine, thus speaking to the efficacy of β-ALA instead to increase carnosine levels . However, Tamaki and coworkers  were able to show an increase in carnosine with histidine in rats .
Aside from the buffering effects, carnosine has shown to have other physiological roles, including that of an effective antioxidant against oxidative stress .
Reactive oxygen species (ROS) can arise from exercise in several proposed mechanisms including: an increase flow of electrons in the electron transport system from increased respiration  or a decrease in pH can lead to oxygen being released from hemoglobin and a subsequent increase in pO2 in the tissues .
Some believe the development of ROS to be related to muscle fatigue during activity [47,48].
Carnosine is also linked to enzyme regulation related to activation of myosin ATPase, which is used to help maintain ATP stores . Finally, carnosine has been noted to have a role in electron- contraction (E-C) coupling in skeletal muscle.
An early study by Lamont and Miller  showed 15 mM of carnosine resulted in a significant increase in Ca2+ sensitivity in muscle fibers of Rana temporaria .
More recently, Dutka and Lamb  examined if carnosine affects E-C coupling in functional fibers under physiological conditions. They used mechanically skinned rat extensor digitorum longus muscle fibers.
Their results showed that carnosine did not affect Ca2+ release from the sarcoplasmic reticulum; however, carnosine was able to increase the Ca2+ sensitivity of the contractile components of the muscle fibers.
Authors suggested the assistance in Ca2+ sensitivity could help maintain force production in the later stages of fatigue once Ca2+ release begins to decrease.
Therefore, higher levels of carnosine can help offset the decrease in Ca2+ as well as the accumulation of H+ ions during high-intensity exercise .
Since carnosine has a number of physiological roles, there are a number of future research opportunities. Specifically, the exact mechanism of carnosine in its role to improve exercise performance and/or reduce muscular fatigue needs to be studied.
It will also be important to examine how different nutritional strategies to increase carnosine levels in the muscle may optimize physiological activity and/or exercise capacity.
β-ALA is a naturally occurring amino acid that is one of the precursors to carnosine, along with L- histidine. Carnosine synthetase is the enzyme used to synthesize carnosine from β-ALA and L- histidine. β-ALA is also likely to be the rate-limiting step in the synthesis of carnosine [14,52,53].
Carnosinase is the enzyme present in cells and serum that breaks down carnosine into β-ALA and L-histidine .
β-ALA supplementation in doses greater than 10 mg/kg of body weight has shown to cause a short period of paraesthesia with increasing severity as the dose increases.
However, when a large dose around 40 mg/kg of body weight is ingested with CBEX, the paraesthesia did not occur.
It is hypothesized that this side effect is a result of the rapid high peak blood plasma concentrations of β- ALA with supplementation alone, since it is not experienced when β-ALA is ingested through the diet with histidine containing dipeptides such as carnosine in meat products .
Beta-Alanine and Carnosine
As previously mentioned, β-ALA supplementation has recently been shown to significantly increase intramuscular carnosine levels, which then corresponds to improvements in exercise performance .
Harris and colleagues  examined the effects of β-ALA supplementation on human skeletal muscle carnosine concentration in a series of studies.
In one study, investigators examined the effects of four weeks of β-ALA or carnosine supplementation on muscle carnosine concentrations. The supplementation protocol included consuming 800 mg of β-ALA four times a day (i.e., 2.3 g/day) for a total intake of approximately 90 g over the four week period (group I) or increasing doses of β-ALA through the supplementation period (average 6.4 g/day) for a total intake of about 146 g over the four week period (group II).
The carnosine supplementation group involved consuming increasing doses of L-carnosine through the supplementation period for a total intake of 364 g of L-carnosine over the four week period which corresponded to an intake of about 143 g of β-ALA. A final group supplemented with maltodextrin as a placebo in the same frequency as the β-ALA and L-carnosine supplementation groups.
A muscle biopsy was taken before and after supplementation. Results revealed that each supplement group showed significant increases in carnosine content. Mean carnosine content increase (measured in mmol·kg-1dm) was greatest with L-carnosine and was followed by groups II and I of β- ALA with values of 16.37 ± 3.03 (p < 0.05), 11.04 ± 2.68 (p < 0.05) and 7.80 ± 0.36 (p < 0.05) mmol·kg-1dm, respectively.
There was no change in the placebo group (1.87 ± 1.73, p>0.05 mmol·kg- 1dm). This corresponded to percent changes of 66%, 64%, 42%, and 10% for L-carnosine, group II, group I and placebo group, respectively.
They also indirectly calculated the contribution of carnosine to buffering capacity between pH levels of 7.1 and 6.5 using the Henderson-Hasselbach equation.
They found that after four weeks of supplementation, carnosine accounted for about 14.2%, 14.3%, and 12.6% of the total muscle buffering capacity in the L-carnosine group, group II, and group I, respectively .
Studies have also suggested that there does not appear to be an upper limit on increasing muscle carnosine concentrations.
For example, Derave and colleagues  supplemented trained male sprinters with β-ALA or placebo (maltodextrin) for four to five weeks.
The supplementation protocol included six daily doses of 400 mg capsules of either β-ALA or maltodextrin totaling 2.4 g/day for the first four days, 3.6 g/day for the next four days, and 4.8 g/day for the duration of the study.
Interestingly, muscle carnosine levels were increased even in individuals with high resting muscle carnosine concentrations .
While β-ALA and carnosine supplementation have been reported to increase muscle carnosine levels, less is known about the time course of carnosine degradation.
Carnosinase is responsible for the hydrolyzation of carnosine and is mainly present in human plasma, which is why carnosine levels are much lower in the blood than in skeletal muscle, where this enzyme is not present .
β-ALA supplementation in doses of 4-6 g/day over time has been shown to increase carnosine by 20-30% after two weeks, by 40-60% after four weeks, and up to 80% by ten weeks [6,55].
A study by Baguet and colleagues  sought to determine the loading phase of carnosine and the time course of removal.
They included 20 males who supplemented with either β-ALA or maltodextrin as a placebo for five to six weeks. The investigators provided doses of 2.4 g/day for days one and two, 3.6 g/day for days three and four, and 4.8 g/day for the remainder of the study duration.
Using a proton magnetic resonance spectroscopy (MRS), they measured the carnosine content in three different muscles (soleus, tibialis anterior, and gastrocnemius) at four time points (pre-supplementation, during the last week of supplementation and at weeks three and nine following the cessation of supplementation).
They determined that carnosine elimination occurs relatively slowly and in a linear pattern at an average rate of 0.21 mM/week in both type I and II fibers. Authors suggest the slow clearance of carnosine is indicative of the high stability of the metabolite . Table 1 provides a summary of recent studies examining the effects of β-ALA supplementation on carnosine concentrations.
Table 1. Summary of the effects of β-ALA supplementation on muscle carnosine concentrations.
|Authors||Population||Supplementation Protocol||Muscle Carnosine Concentration Effects||Performance Results|
|Baguet et al., 2009 ||20 physically active males||5-6 weeks of β-ALA or placebo (maltodextrin) 2.4 g/day – first 2 days 3.6 g/day – days 3-4 4.8 g/day to end of study||In soleus, carnosine increased 30% (p=0.003) with β-ALA and remained stable with placebo (p=0.867)In tibialis anterior, carnosine increased 27% (p=0.005) with β-ALA and decreased 17% (p=0.05) with placebo In gastrocnemius, carnosine increased 23% (p=0.038) and did not change with placebo (p=0.740).Carnosine elimination was measured at 3 and 9 weeks after supplementation period At 3 weeks, only 26.1% (in the soleus), 20.1% (in tibialis anterior) and 44.7% (in the gastrocnemius) of the increase had disappeared. There was no difference between β-ALA and placebo at this point (p=0.431)At 9 weeks, carnosine levels in all 3 muscles returned to initial values||None measured|
Table 1. Cont.
|Harris et al., 2006 ||Study 3: 21 physically active males Ages 26.1 ± 5.6 yrs||4 weeks, 4 groups (I – IV): 800mg β-ALA x 4 daily (avg. 3.2g daily and 89.6g 4wk total)8 daily doses of either 400 or 800mg β-ALA (avg. 6.4g daily and 145.6g 4wk total)8 daily doses of 1000 or 2000 mg L- carnosine (364g 4wk total L-carnosine, corresponding to 143.3g β-ALA)Placebo of maltodextrin at doses to match groups II and III||Increase in carnosine concentration greatest with carnosine supplementation, followed by group II, then group II β-ALA protocols.Mean increase over 4 weeks (mmol·kg-1dm) I) 7.80 ± .36 (p < .05) II) 11.04 ± 2.68 (p < .05) III) 16.37 ± 3.03 (p < .05) IV) 1.87 ± 1.73 (p>.05)||None measured|
|Derave et al., 2007 ||15 male track athletes (sprinters) 18-24 yrs||4-5 weeks β-ALA or placebo (maltodextrin) 2.4g/day – first 4 days 3.6g/day – days 5-8 4.8g/day to end of study||Soleus: ↑ 47% with β-ALANo change with placebo Gastrocnemius:↑ 37% with β-ALANo change with placebo||No difference between groups for 400m running performance|
|Hill et al., 2007 ||25 physically active males||10 weeks β-ALA: 4g/day – wk 1 4.8g/day – wk 2 5.6g/day – wk 3 6.4g/day – wk 4-10||β-ALA group, ↑ from 19.0 to 30.1 mmol/kg (58.8%) at 4 weeks and up to 34.7 mmol/kg (80.1%) at 10 weeks Not significant between weeks 4 and 10||No effect on body mass↑cycling capacity time at 110% with β-ALA|
Beta-Alanine and Exercise Performance
Increases in muscle carnosine due to β-ALA supplementation have resulted in significant effects on several variables related to exercise performance.
Some of these include improved time to fatigue on a maximal cycle test , increased ability to sustain power output in the final ten seconds of the Wingate test , delayed onset of neuromuscular fatigue during incremental cycle ergometry tests as noted by increased physical working capacity (PWCFT), increased ventilatory threshold (VT) and time to exhaustion (TTE) , and improvements in muscle torque during repeated bouts of intense dynamic contractions .
Since studies have reported that muscle carnosine levels are typically higher in fast-twitch muscle fibers, which are most predominantly used in high-intensity anaerobic exercise bouts, it has been hypothesized that β-ALA supplementation could aid in anaerobic performance.
In 2002, Suzuki and colleagues  performed a study that did not involve any nutritional supplementation, but simply analyzed muscle biopsy samples from the vastus lateralis before and after a 30-second maximal cycle sprint Wingate test.
The muscle samples were analyzed for carnosine content. Analysis showed a direct relationship between carnosine concentration in skeletal muscle and performance on the 30- second Wingate exercise test.
This relationship lends itself to the question of efficacy of β-ALA supplementation in further improving anaerobic exercise performance.
Hill and coworkers  examined the effects of four and ten weeks of β-ALA supplementation on muscle carnosine concentration and high-intensity cycling capacity.
They also sought to discover whether the effects were muscle type specific. Physically active males supplemented with either β- ALA or maltodextrin as a placebo. β-ALA was given in eight doses per day with increasing dose amounts during the first four weeks ranging from 250-750 mg per dose.
Subjects underwent muscle biopsies and maximal cycle performance tests at various points during the study. The group supplementing with β-ALA had significantly greater muscle carnosine concentrations at four and ten weeks from 19.9 ± 1.9 to 30.1 ± 2.3 (30.4%) and 34.7 ± 3.7 (35.1%) mmol·kg-1dm.
There was no significant change with placebo. The change between four and ten weeks with β-ALA was not significant despite the small increase (p~0.07).
The results also indicated no difference between fiber types, in that each showed similar increases in carnosine as measured by HPLC with fluorescence detection. The authors suggested that the possible benefits from β-ALA supplementation may be limited to four weeks, which is in agreement with previous findings by Suzuki and coworkers  who showed an increase in the ability to sustain power output after four weeks of supplementation with no additional benefits observed at ten weeks .
Limited research has examined the effects of β-ALA on sport-specific anaerobic performances. Derave and colleagues  studied the effects of a four week supplementation period on athletic performance, using a 400 m running race time trial.
The researchers found no significant differences in performance after supplementation, but suggested this may have been due to the short time period of supplementation since it takes several weeks to induce carnosine loading.
Using a proton MRS to detect muscle carnosine concentrations, investigators showed an increase in carnosine concentrations of 47% in the soleus muscle after β-ALA supplementation with no significant increase after placebo supplementation (8%).
Both groups showed significant increases in carnosine concentrations in the gastrocnemius but subjects supplementing their diet with β-ALA observed a greater increase (37% versus 16%) . This is in contrast to the previously discussed study that reported performance improvements after four weeks of supplementation .
The researchers suggested that this may be due to the possibility that in trained athletes, a 400 m running performance is not necessarily limited by the intracellular pH decrease, and therefore the buffering capabilities of the increased carnosine concentrations would not be as critical of a component .
Another recent study sought to determine whether β-ALA supplementation would affect endurance cycling performance. Van Thienen and colleagues  evaluated whether β-ALA supplementation would enhance the final sprint performance during endurance cycling since many competitions are won in the final seconds of the race after an all-out sprint.
They studied 21 trained males who supplemented their diet with either β-ALA or a maltodextrin placebo for eight weeks.
The dose gradually increased from 2 g/day for the first two weeks, 3 g/day for weeks three and four, to 4 g/day for weeks five to eight. The exercise test involved 110 minutes of cycling in ten minute stages with increasing intensity between 50–90%.
Following this, the subjects performed a 30 second all-out sprint. The researchers reported that β-ALA supplementation increased sprint peak power after a two hour endurance exercise bout by 11–15% (p=0.0001) and mean power output by 5–8% (p = 0.005) .
In contrast to trained individuals, Smith and colleagues  recently examined the combined effects of six weeks of β-ALA supplementation and high-intensity interval training on endurance performance in recreationally active males.
In this study, 46 participants were randomly assigned to either β-ALA or placebo supplementation groups. Both groups trained at 90–110% of their peak oxygen utilization (VO2peak) for the first three weeks, followed by three weeks of training at 115% VO2peak.
During the training, they continually supplemented with 6 g/day of β-ALA or a dextrose placebo for the first three weeks and 3 g/day for the second three weeks. They showed increases in both groups for VO2peak, time to reach VO2peak, and total work done.
However, the group ingesting β-ALA observed a greater increase in VO2peak and time to reach VO2peak during the second three weeks of the training protocol (p < 0.05), with no change in the placebo group.
They also noted a significant increase in lean body mass for the β-ALA group after the first three weeks. These results suggest that β-ALA supplementation may enhance the effects of high-intensity interval training and improve endurance performance in untrained individuals.
Additionally, Smith and colleagues  examined the effects of the same high-intensity interval training and β-ALA supplementation protocol described above on neuromuscular fatigue and function.
The researchers reported that three weeks of the interval training was sufficient to result in a significant increase in the EMG fatigue threshold (EMGFT). However, β- ALA supplementation did not promote greater benefits . Table 2 presents a summary of recent studies examining the effect of β-ALA supplementation and carnosine loading on exercise performance.
Table 2. Summary of recent β-ALA supplementation and exercise performance studies.
|Authors||Population||Supplementation Protocol||Exercise Testing Protocol||Performance Results|
|Stout et al., 2006 ||51 males||4 groups: Placebo – 34 g dextroseCreatine – 5.25 g creatine monohydrate and 34 g dextroseβ-ALA – 1.6 g β-ALA plus 34 g dextroseβ-ALA+Creatine – 5.35 g creatine monohydrate, 1.6 g β- ALA and 34 g dextrose 28 days of supplementation: 4 doses/day – days 1-62 doses/day – days 7- 28||PWCFT test with EMG measurements on a cycle ergometer||β-ALA may delay the onset of neuromuscular fatigue, but no additive effects of creatineSignificant increase in PWCFT with β-ALA (14.5%) and creatine plus β- ALA (11%) compared to placebo|
|Stout et al., 2007 ||22 females Ages: 28.9 ± 8.1 yrs (β-ALA) 25.8 ± 4.0 yrs (placebo)||4 weeks β-ALA or placebo4 divided doses/day for totals of:3.2g/day – days 1-76.4g/day – days 8-28||Continuous graded exercise test on cycle ergometer for VO2max, ventilatory threshold , PWCFT and TTE||β-ALA delays onset of NMF during incremental cycle ergometry (↑ PWCFT, ↑VT, ↑TTE)|
|Stout et al., 2008 ||26 elderly males and females||90 days supplementation with β-ALA or placebo (microcrystalline cellulose) 3 doses/day of: 2.4 g β-ALA or 2.4 g placebo||Continuous graded exercise test on cycle ergometer for PWCFT with EMG measurements||28,5% increase in PWCFT after 90 days of β-ALA|
|Sweeney et al., 2009 ||19 physically active college-aged males||5 weeks β-ALA or placebo (rice flour) 4g/day – week 16g/day – weeks 2-5||2 sets of 5×5-sec sprints with 45- sec recovery between sprints and 2 min between sets performed on non- motorized treadmill at 15% body weight as resistance||No between group difference for peak or mean horizontal powerNo difference in % fatigueNo difference in blood lactate pre- and post-testing between groups|
|Van Thienen et al., 2009 ||17 healthy young males||8 weeks β-ALA or placebo (maltodextrin) 2 g/day – weeks 1-23 g/day – weeks 3-44 g/day – weeks 5-8||Simulated road race of 110 minutes intermittent endurance with intensity between 50% and 90% of the maximal lactate steady state (MLSS) in 10 minute stages. Immediately after this, they started a 10 minute time trial at 100% MLSS with voluntary increase of intensity at each minute.||β-ALA enhanced sprint power output at the end of the endurance race compared to placebo|
|Zoeller et al., 2007 ||55 males ages 24.5 ± 5.3 yrs||4 weeks, 4 groups (4 doses/day for first 6 days, then 2 doses/day Placebo – 34g dextroseCreatine – 5.25g creatine monohydrate and 34g dextroseβ-ALA – 1.6g β-alanine and 34g dextroseβ-ALA plus Creatine – 5.25g creatine monohydrate, 1.6g β- ALA and 34g dextrose||Continuous graded exercise test on cycle ergometer||↑ in 5 cardio-respiratory endurance variables with creatine + β-ALACombined supplementation may delay the onset of VT and lactate threshold during incremental cycle exercise|
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More information: Elaheh Mahootchi et al. GADL1 is a multifunctional decarboxylase with tissue-specific roles in β-alanine and carnosine production, Science Advances (2020). DOI: 10.1126/sciadv.abb3713