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Numerous manuals, self-study guides, and articles aimed at athletes commonly mention the use of amino acid supplements. These supplements are believed to assist in gaining muscle mass quickly, increasing strength and endurance, and aiding in weight loss.
Amino acid supplements have gained significant popularity and are predicted to generate sales of $302.07 million in powders and capsules containing valine, isoleucine, and leucine (also known as BCAAs) by 2022, with prices starting at $10 for the smallest package.
This article aims to distinguish between essential amino acids that are beneficial for athletes and those that are not necessary.
Amino acids: what are they and why are they needed
What are amino acids?
Organic molecules, consisting of carbon, nitrogen, oxygen, and hydrogen, are referred to as amino acids. Out of the numerous organic molecules, the twenty amino acids are of utmost significance, as they are responsible for constructing the proteins of all living organisms, ranging from bacteria to humans.
Although amino acids are ingested into the body through the consumption of ready-made proteins in food, plant and animal proteins differ significantly from human proteins. Therefore, it is essential for the body to break down foreign proteins into amino acids to develop its own proteins, including enzymes and protective antibodies.
In addition to their role in protein synthesis, amino acids are required for other bodily functions. For instance, tryptophan is necessary for producing serotonin, a neurotransmitter responsible for happiness, and vitamin B3, also known as niacin. Moreover, glutamate, a salt of glutamic amino acid, serves as a neurotransmitter and aids in the communication of nerve cells in the brain.
Furthermore, unused amino acids can serve as a supplementary source of energy for the body, providing up to 10% of total energy during intense physical activities.
What are amino acids?
To maintain a healthy life, all twenty amino acids are necessary for humans, but they hold different values in terms of their importance to the human body.
Nine amino acids are considered crucial as our bodies are incapable of producing them. Thus, they must be obtained in their complete form from food, and they are referred to as essential amino acids. These essential amino acids include valine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, phenylalanine, and histidine.
Sources of complete protein are products that contain all nine essential amino acids, such as beef, poultry, fish, eggs, dairy products, soy, and buckwheat. Conversely, products that lack any essential amino acid are deemed incomplete proteins, such as nuts, seeds, and legumes. To prevent a deficiency, a vegetarian diet must consist of a diverse range of foods, as different plants lack varying essential amino acids.
The remaining eleven amino acids can be created by our bodies from other substances and the essential amino acids obtained from food. They are known as non-essential or replaceable amino acids, which include alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
Healthy adults can synthesize the eleven essential amino acids in sufficient quantities. However, individuals who are recovering from injuries or illnesses, rapidly growing teenagers, and pregnant women may not have an adequate amount. Conditionally essential amino acids, which are often deficient, include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.
How many amino acids do we need?
The requirements for amino acids differ based on gender, age, and health conditions. While there is no deficiency in essential amino acids, only the needs for non-essential amino acids are measured. Nonetheless, various organizations have varying assessments of these requirements.
For this article, the report of the World Health Organization will be utilized as it is based on data gathered globally rather than solely within one country.
Do amino acids help you lose weight?
Using amino acid supplements alone as a weight loss strategy is ineffective since they do not burn fat on their own. However, those who derive their energy from protein tend to accumulate fat more slowly than those who consume carbohydrate-rich foods. Protein is made up of three types of amino acids:
- Gluconeogenic amino acids, which are converted to glucose in the body. Valine, methionine, histidine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, and serine are the most common gluconeogenic amino acids.
- Ketogenic amino acids, which do not convert to glucose. They are fully metabolized in the energy cycle, with hydrogen and oxygen converted to water, nitrogen excreted with urine, and carbon exhaled with carbon dioxide. Leucine and lysine are the only true ketogenic amino acids.
- Ketogenic and glucogenic amino acids, which can be converted to glucose or fully metabolized in the ketogenic cycle, depending on the body’s current needs. These amino acids are phenylalanine, isoleucine, threonine, tryptophan, and tyrosine.
Protein-rich diets are based on the principle that proteins are composed of both glucogenic and ketogenic amino acids. Thus, those who primarily consume protein-rich foods have less glucose in their bodies than those who consume carbohydrate-rich foods and tend to gain less weight.
Although protein diets can be effective in reducing weight, they may not work always. Some of the protein still converts to glucose, so overeating protein can still lead to weight gain. Furthermore, high-protein diets are not suitable for everyone.
In theory, temporarily replacing complete protein with a set of amino acids, many of which are ketogenic, may result in even faster weight loss. Attempts to use amino acid supplements in this way have been made, and the results will be discussed in sections dedicated to these amino acids.
Next, beneficial amino acids for sports training will be discussed, and various supplement brands will be used as examples. The price of supplements depends on the manufacturer’s pricing policy, as well as the volume of packaging or the number of amino acids per capsule within a product line.
Which amino acids will you learn about?
- Branched-chain amino acids: valine, isoleucine, leucine (BCAA)
- Alanine
- Arginine
- Aspartic acid
- Histidine
- Glycine.
- Glutamine
- Methionine
- Threonine
- Cysteine
- Citrulline
- Phenylalanine and tyrosine.
Branched chain amino acids (BCAA): valine, isoleucine, leucine.
What is BCAA? The amino acids that are essential for the body are valine, isoleucine, and leucine. These three amino acids make up approximately 17% of all amino acids found in muscles.
Leucine has a dual function in that it acts as a building block for muscle protein while also controlling the process of its assembly. During physical activity, the presence of leucine triggers the synthesis of new protein chains, contributing to muscle growth. Leucine is also classified as a ketogenic amino acid. Hence, in theory, it is possible to lose weight faster by reducing calorie intake and temporarily substituting sources of complete protein with BCAA.
Isoleucine, on the other hand, helps muscle cells absorb more glucose, which improves their nutrition. Valine may also have a positive impact on muscle metabolism, but its precise role is yet to be determined.
What foods are rich in BCAA? Red meat and dairy products are the most abundant sources of BCAA. However, for vegetarians, a mixture of legumes, nuts, cereals, and seeds can provide all three amino acids.
Daily recommended intake for adults is 39 mg/kg of leucine, 20 mg/kg of isoleucine, and 26 mg/kg of valine.
What is the reason for their usage in sports? According to numerous sports textbooks, athletes require a greater amount of leucine, isoleucine, and valine compared to other amino acids in order to enhance muscle protein synthesis and promote muscle growth. Certain supplement manufacturers promote the idea that BCAAs can reduce physical discomfort, diminish fatigue, enhance athletic performance, and even aid in weight loss.
The effectiveness of supplements for muscle growth
Theoretically, BCAA supplements should increase muscle mass as they enhance the signal for muscle growth by increasing the amount of leucine present in muscles during physical exertion. However, the practical application of BCAA supplements is not as straightforward.
Studies show that BCAA supplements contribute to muscle growth in individuals who engage in intense training. On the other hand, there is no compelling evidence to suggest that athletes who do not take supplements but consume enough protein from food have worse muscle development.
For example, a 100-gram serving of boiled chicken breast contains approximately 24 grams of protein, including 2.18 grams of leucine, 1.22 grams of valine, and 1.21 grams of isoleucine. An adult athlete’s protein requirement is typically 1.4-2 grams per kilogram of body weight per day.
Suppose an athlete who weighs 60 kg decides to obtain their daily protein intake solely from chicken. In that case, they would receive 10.9 grams of leucine, 6.1 grams of valine, and 6 grams of isoleucine, which equates to over 20 grams of BCAA per day.
To put it into perspective, one serving of BCAA supplement contains 12 grams, including only 3 grams of leucine, 1.5 grams of valine, and 1.5 grams of isoleucine. Therefore, an individual would need to consume approximately four servings to obtain the same amount of amino acids from the supplement as from a 100-gram serving of chicken breast. However, supplement manufacturers recommend consuming no more than two servings at a time.
In reality, most people obtain their protein from various sources, such as eggs, cottage cheese, soy, and legumes, in addition to chicken. Even with this varied protein intake, the amount of BCAAs is still more than sufficient, even for intense workouts, as they are present in these protein sources in almost the same amounts as in chicken.
Authoritative sports associations suggest that a drink containing 2-4 grams of BCAA may only be useful for athletes who have insufficient protein intake or vegans who consume low-protein plant-based dishes such as green salads during and after training.
For athletes who have access to quality protein foods and for vegans who consume a variety of plant-based protein, obtaining BCAAs from food is the best option. Unlike supplements, foods such as chicken breast contain not only a high amount of leucine, valine, and isoleucine but also essential vitamins and minerals necessary for a healthy lifestyle.
Regarding the effectiveness of BCAA supplements in reducing muscle pain, a six-year study has demonstrated that athletes who consumed this supplement before exercising experienced less muscle soreness afterward. However, no comparison has been made between BCAA and regular protein food. It is possible that if athletes consumed nuts, meat, or milk before exercise, they may also experience less muscle pain.
The effectiveness of the supplement for reducing fatigue. It has been suggested that BCAA supplements may help reduce fatigue. During intense training, certain amino acids, such as leucine, are depleted more rapidly than others, like tryptophan. Consequently, a higher amount of tryptophan than usual enters the brain. The neurotransmitter responsible for fatigue, 5-hydroxytryptamine, is synthesized from tryptophan. As a result, an individual may feel tired before fully exhausting their energy. However, if an athlete has a high concentration of leucine in their bloodstream, this amino acid can compete with tryptophan to cross the blood-brain barrier, which is the selective wall of blood vessels in the brain. Therefore, the brain may not identify that there is an increase in tryptophan, and the athlete may feel less tired.
Some experiments have shown that adding BCAA to a diet may help avoid premature fatigue during exercise. Nonetheless, it is uncertain if the three amino acids in BCAA are responsible for this effect since all experiments utilized a calorie-free drink, i.e., a placebo. It is plausible that athletes who drank the BCAA cocktail were less tired because they were fueled during exercise while those who did not drink were trained on an empty stomach.
Supplements are often used to enhance athletic performance, but in the case of BCAA, they do not seem to be effective. In a study involving runners in a 100 km race, consuming 20 grams of BCAA supplements did not improve their performance. The runners who took BCAA supplements achieved the same results as those who consumed their typical drinks and protein-rich food.
The effectiveness of weight loss supplements. BCAA supplements have not been demonstrated to be effective for weight loss. Previous studies on obese individuals suggested that BCAA supplements did not result in weight loss. However, a final conclusion was drawn from a 16-week experiment in which individuals who were losing weight received diets with equal calorie content. One group received a standard diet where protein accounted for 16% of the energy, the second group received a diet with increased protein content of 27%, and the third group received BCAA instead of protein. All three groups of participants lost weight in the same manner.
In the end, the Australian Sports Commission and other reputable sports organizations advise against the use of BCAA supplements by athletes. It is advised that individuals who consume adequate amounts of diverse protein sources obtain these amino acids alongside their meals for maximum benefits.
Alanine
What is this? It is a replaceable amino acid that exists in two forms. To understand the difference, we need to say a few words about how these substances are structured.
All amino acids are organic compounds consisting of two parts:
1. R-group, unique for each amino acid. For example, for alanine it is -CH3.
2. The “skeleton” common to all is based on the carbon atom, denoted as C. This fundamental atom is conventionally called alpha-carbon. Attached to it are the amino group -NH2, the carboxyl group COOH, and the unique R group.
Alanine differs from most other amino acids in that it has a non-standard form. Thus, there are two alanines in nature:
- Alpha-alanine. It is a common replaceable amino acid, one of the building blocks that make up proteins. Its amino group is attached to the alpha-carbon.
- Beta-alanine. This is a non-essential amino acid with a unique structure that is not part of proteins. Its amino group is attached to the beta-carbon. And since there are only three carbon atoms in alanine, it turns out that the amino group is attached to the R-group.
Alpha-alanine does not possess any notable characteristics, thus supplements for it are not produced. On the other hand, beta-alanine is able to enter skeletal muscles and combine with histidine to create muscle carnosine.
Carnosine, a natural antioxidant, has a significant impact on athletes due to its ability to prevent the accumulation of lactic acid in muscles during intense exercise. By preventing acidification, carnosine reduces muscle fatigue and soreness, making it a valuable supplement for athletes.
What products contain beta-alanine? Beta-alanine can be obtained by consuming animal products such as red meat, poultry, fish, and dairy, or by synthesizing it in the liver.
Daily requirements for adults are not determined for alpha- and beta-alanine since they are non-essential amino acids.
Why is beta-alanine used in sports? Beta-alanine supplements are taken to increase carnosine synthesis, which can ultimately reduce muscle fatigue during exercise, improve endurance, and enhance athletic performance. However, taking pre-formed carnosine supplements is ineffective since it rapidly breaks down into beta-alanine and histidine in the body.
Evidence of the effectiveness of alanine has been well-established, with beta-alanine being one of the most successful sports supplements available. Studies have shown that a daily intake of 3.2-6.4 grams of beta-alanine for 4-24 weeks can significantly increase the levels of carnosine in muscles.
The added carnosine in the muscles helps to delay the onset of pain during workouts, enabling athletes to perform exercises for a longer duration of time. However, it is essential to note that taking beta-alanine supplements only once or twice a week before a workout will not result in any noticeable benefits. The International Society of Sports Nutrition recommends a daily intake of beta-alanine for at least a month to see optimal results.
Beta-alanine supplements that also contain histidine are believed to enhance performance in sports that involve short bursts of high-intensity effort, such as short distance running. However, it may not be as beneficial for sports that require prolonged effort, such as cycling.
It is important to note that while additional carnosine can help to delay muscle pain during exercises that last 10-30 minutes, it may not be effective for prolonged workouts that last several hours. Lactic acid will still be produced, even with the presence of carnosine.
Consuming beta-alanine in doses of 3.2-6.4 grams at once may cause paraesthesia, a tingling sensation in the muscles that is harmless but unpleasant. To avoid this issue, it is recommended to take smaller doses of 0.8-1.6 grams every 3-4 hours.
Beta-alanine has been recognized as a valuable supplement to enhance athletic performance by experts from the Australian Sports Commission and other reputable organizations. The recommended daily intake for athletes is 6.4 grams of beta-alanine per day, taken in doses of 1.6 grams three times a day with main meals and once with the largest snack of the day. It is suggested that this regimen be followed for at least a month to experience optimal results.
Arginine
Arginine is an amino acid that can be conditionally replaced in the body. Apart from its role in protein synthesis, it serves several other functions in the body. Athletes may benefit from four of its significant functions:
- Acceleration of the release of growth hormone, which plays an important role in gaining muscle mass.
- Acceleration of insulin release, which carries glucose from the blood into cells. This amino acid could improve the efficiency of glucose utilization that athletes obtain from their diet – in other words, it could make more glucose available to intensively working muscle cells and less stored as fat tissue.
- Increase blood flow. The body uses some amount of arginine to produce nitric oxide – a substance that dilates blood vessels and improves blood flow. Theoretically, improved blood flow could enhance muscle respiration and nutrition, which in turn could help delay fatigue.
- Creatine synthesis in muscles. Creatine is synthesized from three amino acids: arginine, glycine and methionine. In muscles, 65% of creatine is converted into phosphocreatine. This substance participates in the recharge of ATP molecules – the main batteries of the body, which supply energy to muscle cells. Therefore, creatine allows athletes to train longer and ultimately makes them stronger.
Arginine can be found in various products, with particularly high levels in white meat such as poultry and fish, as well as in red meat, dairy products, nuts, and seeds.
The daily requirement for arginine is not calculated as it is considered a conditionally essential amino acid.
In sports, arginine is often used to enhance muscle growth, boost exercise performance, and increase energy levels by increasing the concentration of phosphocreatine in muscles.
Evidence of the effectiveness of arginine. Arginine plays an active role in the release of hormones and the regulation of blood flow. When consumed with protein-rich food, the body obtains the precise amount of this amino acid required to sustain these processes at a healthy and normal level.
To enhance the dilation of blood vessels and secretion of growth hormone with insulin, according to some data, it is necessary to regularly take arginine in doses of 6 grams, while according to others – up to 13 grams per day.
However, even in this case, the effect will be very weak. For comparison, an hour of moderate physical activity significantly increases the level of growth hormone in the blood more than daily consumption of 6 grams of arginine for a month.
If you increase the dosage, the effect will be stronger. But it is not safe to do so, as doses greater than 9 grams per day of arginine can cause nausea, abdominal pain, and diarrhea.
The situation with creatine is slightly more complicated. There is compelling evidence that if you take 3-5 grams of additional creatine with supplements for a month, the level of phosphocreatine in the muscles begins to increase. And there is a noticeable benefit from this: the results of athletes who took a course of creatine are slightly better than those who did not take it.
However, it is not recommended to exceed the recommended dose: this substance retains water in the body, so an athlete may develop edema.
At the same time, there is no compelling evidence that creatine precursor supplements increase levels of creatine in the body and phosphocreatine in the muscles.
The Australian Sports Commission and other reputable sports organizations do not endorse supplements that contain creatine precursors, such as arginine, as beneficial for athletes. It is suggested that individuals who consume a diverse protein diet obtain this amino acid through their food intake.
The recommendation only includes supplements that contain “ready-made” creatine, which should be taken at a dosage of 3-5 grams per day for approximately four weeks. It is not recommended to consume them for an extended period, as it may result in edema.
Aspartic acid
Aspartic acid is a type of amino acid that can be substituted in the body. It is present in two mirror spatial forms, namely L and D. The location of the amino group is different for these forms; it is on the left for L-aspartic acid and on the right for D-aspartic acid. Despite the subtle distinction, the two forms of aspartic acid exhibit different functionalities in the body.
L-aspartic acid is employed by the body in various capacities, such as protein synthesis, energy generation, and as a neurotransmitter. Although there are supplements that contain L-aspartic acid, they are not widely utilized. Conversely, D-aspartic acid is not usually integrated into proteins; rather, its role is to boost testosterone and growth hormone levels in the bloodstream.
Athletes and sports supplement manufacturers are particularly intrigued by D-aspartic acid, as heightened testosterone levels can result in increased muscle mass and strength.
Which foods are a source of it? Some examples include oysters, red meat, dairy products, sprouted seeds, oatmeal, and soy. Heating some of these products can cause L-aspartic acid to convert into the D-form, resulting in pasteurized milk containing twice as much D-aspartic acid as unpasteurized milk.
Is there a recommended daily intake for adults? Aspartic acid is categorized as a nonessential amino acid, and therefore, no daily recommended intake is established.
What is the reason for their usage in sports? They are utilized to promote muscle growth and increase strength.
Evidence of the Effectiveness of Aspartic Acid. Currently, we have limited knowledge on how D-aspartic acid affects testosterone levels in the blood. However, it is not realistic to expect that supplements containing this amino acid will help in gaining weight or becoming stronger.
For example, in a study where weightlifters consumed 3 grams of D-aspartic acid daily for 28 days, it did not affect their testosterone levels, muscle mass, or strength. Another study where athletes consumed 6 grams of this amino acid daily for 14 consecutive days even showed a decrease in their testosterone levels, although their muscle mass and strength did not change.
As a result, experts from the Australian Sports Commission and other reputable sports organizations have not included aspartic acid in the list of supplements recommended for athletes. It is more beneficial for individuals who consume a diverse range of protein-rich foods to obtain these amino acids through their diet.
Histidine
Histidine is an amino acid that is not produced in the bodies of children, but is synthesized in adults. The World Health Organization (WHO) considers it to be essential, but some researchers believe that it is conditionally interchangeable.
This amino acid plays a crucial role in the construction of several important proteins and nitrogen-containing non-protein compounds. For instance, it is necessary for the synthesis of hemoglobin – a respiratory protein, and histamine – a neurotransmitter that helps protect our bodies from pathogen invasion.
Athletes are particularly interested in histidine because it aids in the production of muscle carnosine, which is a natural antioxidant that prevents the “acidification” of muscles during intense training and the consequent pain caused by lactate buildup.
Which food items contain it? It can be found in protein-rich foods such as red and white meat, fish, eggs, dairy products, legumes, nuts, seeds, and whole grain products.
The recommended daily intake for adults is 10 mg/kg per day.
What is the reason for its usage in sports? It is used to enhance the synthesis of muscle carnosine, which can help in reducing muscle pain during training, boosting endurance, and improving overall athletic performance. We have previously discussed the evidence supporting its benefits in the section dedicated to alanine.
Although histidine supplements are available, they are seldom used independently. They are typically purchased as an addition to beta-alanine or taken as part of a combination supplement that includes both beta-alanine and histidine.
Histidine’s effectiveness can be demonstrated by the fact that carnosine synthesis requires two amino acids, namely, histidine and beta-alanine. While histidine is an essential amino acid, beta-alanine plays the crucial role of being the limiting factor. This means that without beta-alanine, the body cannot produce additional carnosine.
To summarize, knowledgeable experts from respected sports organizations suggest that supplementing solely with histidine is impractical, leading to the Australian Sports Commission’s exclusion of histidine from the recommended list of athlete supplements. If the individual lacks adequate complete protein intake, histidine should only be supplemented with beta-alanine at a ratio of roughly 1:2. However, athletes with a well-balanced diet may only need to supplement with beta-alanine.
Glycine
Glycine is a type of replaceable amino acid that has a sweet taste. It plays a crucial role in the construction of many essential proteins, including collagen, which is a vital component of tendons and skin. Glycine is also synthesized directly in the nervous system and acts as a natural sedative and anticonvulsant by functioning as an inhibitory neurotransmitter. Athletes are interested in glycine because it participates in the synthesis of two nitrogen-containing substances that affect athletic performance: glutathione and creatine.
Glycine can be found in a wide range of protein-rich foods, such as meat, eggs, soybeans, lentils, and dairy products. As glycine is a replaceable amino acid, there is no set daily requirement for adults.
What is the role of supplements containing glycine in sports? These supplements aim to enhance the synthesis of two crucial substances – creatine and glutathione. However, increasing the concentration of creatine in the body by consuming its precursors is unlikely to be effective, as discussed in the section on arginine. Nevertheless, it is worth highlighting the benefits of glutathione.
Glutathione is an antioxidant synthesized from three amino acids – glycine, glutamine, and cysteine. It protects cells from damage caused by free radicals, which are unstable molecules that can harm cell walls. During physical activity, excess free radicals are believed to be produced, which may slow down muscle recovery and growth after exercise.
Glutathione also regulates the muscles’ response to physical exertion. Some experts suggest that sports supplements containing glutathione may improve muscle adaptation to training, leading to enhanced sports performance.
In certain countries, glycine is marketed as a nootropic, which claims to improve brain function. However, glycine from supplements and medication is unlikely to enter the brain, making it useless for this purpose.
What is the evidence of glycine’s effectiveness? Taking glycine to increase glutathione levels in the body is ineffective as the body already receives enough glycine from food, and glycine does not limit glutathione synthesis. To create additional glutathione in the body, supplements with cysteine are required.
However, even if glycine increased glutathione synthesis, it is not certain that additional glutathione would aid recovery or improve athletic performance. Although athletes with low blood glutathione concentrations appear to suffer more from free radicals after exercise than those with higher glutathione levels, there is little compelling evidence that glutathione supplements speed up recovery or enhance athletic performance.
A single eight-week study found a slight increase in muscle mass and strength in weightlifters taking two grams of glutathione per day. Nevertheless, it is premature to recommend glutathione supplements to athletes until confirmed by other high-quality studies. It is possible that only endogenous glutathione, synthesized by the body from amino acids, facilitates adaptation to training.
Ultimately, experts do not consider glycine supplements beneficial for athletes as they have no impact on either creatine or glutathione synthesis. For individuals who consume sufficient amounts of diverse protein-rich foods, obtaining glycine from food sources is more advantageous.
Glutamine
Glutamine is a type of amino acid that can be conditionally replaced within the body. Its primary function is to assist in the building of proteins and protein-like substances, such as glutathione, which helps the body adapt to physical training. Additionally, immune cells and the intestines rely heavily on glutamine as a source of energy, often consuming it even more than glucose. This has led to the belief that increasing glutamine intake may help boost resistance to infections.
Glutamine can be found in various food sources, including meat, poultry, fish, eggs, and legumes. Dairy products, in particular, are especially rich in glutamine.
Since glutamine is a replaceable amino acid, there is no specific daily recommended intake for adults.
The reason for using glutamine in sports is to enhance athletic performance by promoting the synthesis of additional glutamine and supporting immune system function.
Evidence of the effectiveness of glutamine. Taking glutamine to increase the amount of glutathione in the body is useless, as this amino acid does not limit its synthesis. Why this is important, we wrote in detail in the section dedicated to glycine.
Overall, there is very little convincing evidence that glutamine improves athletic performance in any way.
Athletes who train intensively for endurance – such as elite rowers and long-distance runners – really do catch colds more often than people who engage in other types of sports or don’t train at all. That is why in 1996, the potential of glutamine supplements as a preventive measure was decided to be tested in an experiment.
The researchers divided a group of 200 rowers and runners into two parts. Half received 330ml of mineral water with 5 grams of glutamine after intense training, and the other half received a placebo. They received the second drink two hours after training and then had to record all cases of colds in their diary for a week. Athletes who took glutamine got sick almost three times less often: in 19% of cases compared to 51%.
However, we cannot confidently say that glutamine protects athletes against colds, because no one has studied the preventive possibilities of this supplement for 26 years.
In conclusion, experts from the Australian Sports Commission and other authoritative sports organizations have not included glutamine in the list of supplements recommended for athletes. In terms of effectiveness, athletes who consume a sufficiently varied protein diet would benefit more from obtaining this amino acid through their food.
Methionine
Methionine is an essential amino acid that plays various roles in the body. It functions as an antioxidant, protecting cell membranes from oxidative damage. Additionally, it can bind with heavy metals like lead and mercury, forming compounds that are easier for the body to eliminate. This is especially useful during heavy metal poisoning, as it can reduce the strain on the liver. Methionine is also necessary for the synthesis of many proteins, making it an important nutrient for overall health.
In terms of sports performance, methionine is attractive to athletes because it is a component of creatine, which is a key source of energy for active muscles. It can help increase muscle mass and provide additional energy by increasing the amount of phosphocreatine stored in the muscles.
Methionine can be found in a variety of foods, including fish and seafood, red meat, nuts, soy, tofu, and legumes. The recommended daily intake for adults is 10.4 mg/kg.
Why is it used in sports? To increase muscle mass and obtain additional energy by accumulating additional phosphocreatine in the muscles. Sometimes supplement manufacturers suggest taking it “for detox” and as an additional means of protecting the liver.
Regarding the effectiveness of methionine, there is insufficient evidence to support the notion that amino acid precursors can boost the creatine levels in muscles. This was discussed extensively in the section dedicated to arginine.
There is currently no evidence that additional methionine protects the liver or removes any harmful substances from the body other than heavy metals.
In the dosages found in supplements, methionine does not harm health, but it is unlikely to provide any benefits either.
In summary, experts do not consider supplements containing creatine precursors, such as methionine, to be advantageous for athletes. It is suggested that individuals who consume a varied protein diet obtain this amino acid through their food intake instead.
On the other hand, supplements that contain “ready-made” creatine have been included in the recommendations of leading sports organizations, including the Australian Sports Commission. It is recommended to consume these supplements in doses of 3-5 grams daily for roughly four weeks, and taking them for longer periods is not advised due to the risk of edema.
Threonine
Threonine is an essential amino acid with multiple functions in the body, including its role in fat metabolism and as a component of mucus which maintains intestinal health. It is also necessary for protein synthesis. For athletic performance, threonine is particularly important as it is converted to glycine, which is a building block of glutathione. Glutathione aids in adapting to intense workouts, making it an important supplement for athletes.
Threonine is found in a variety of foods such as red and white meat, fish and seafood, tofu, dairy products, seeds, nuts, and legumes. The daily recommended intake for adults is 15 mg/kg.
Sports supplement manufacturers recommend taking threonine supplements to increase glutathione synthesis in the body, which may promote muscle recovery and growth after exercise.
Evidence of the effectiveness of threonine. We wrote in detail in the section devoted to glycine why additional glycine will not help to get more glutathione. Despite claims in advertising, there is no proven benefit of threonine supplements for athletes.
In the end, experts from the Australian Sports Commission and other authoritative sports organizations do not include threonine supplements in the list of beneficial supplements for athletes. From the standpoint of effectiveness, for athletes who consume a sufficiently varied protein diet, it is more beneficial to obtain this amino acid through their food.
Cysteine.
WHO considers cysteine an essential amino acid, although some organizations classify it as conditionally essential.
Cysteine plays a significant role in the synthesis of several essential proteins. One such example is its ability to bind with iron, which is necessary for the proper functioning of the respiratory enzyme hemoglobin. However, for athletes, its importance lies mainly in its role in synthesizing two crucial substances.
- Glutathione, which helps adapt to training loads.
- Taurine, which strengthens the cardiovascular system and increases the sensitivity of muscle proteins to calcium. According to some data, this increases muscle strength and endurance.
Which foods are rich in it? Some dietary sources include chicken, eggs, fish, seeds, nuts, and whole-grain products.
The recommended daily intake for adults is around 4.1 mg/kg.
Why are these compounds popular in sports? They are believed to enhance performance by providing an extra dose of glutathione and boosting muscle strength through taurine supplementation.
The effectiveness of the supplement for glutathione synthesis. Cysteine limits glutathione synthesis. Therefore, the more of this amino acid in the body, the more additional glutathione it can create.
However, apparently, a monthly daily intake of supplements containing 1.2 grams of cysteine helps only those athletes whose blood had an initially low level of glutathione – and after this, these people really started to exercise slightly more effectively. For athletes with normal glutathione levels, the concentration of glutathione in the blood did not change after taking the supplement, and this did not affect their athletic performance.
However, this study alone is not enough to recommend cysteine supplements for athletes. First, the effect needs to be confirmed in qualitative studies – and then a cheap and quick way to determine which athletes have a glutathione deficiency and which do not needs to be devised. This is important because supplements will not help people without a glutathione deficiency, and people with a serious deficiency may not get enough from just 1.2 grams. At doses higher than 3 grams per day, cysteine can cause nausea, diarrhea, and bloating.
The effectiveness of the additive for the synthesis of taurine. It seems that the synthesis of taurine in the body really depends on the concentration of cysteine, which enters the body along with supplements. But even if so, the benefits of additional taurine have yet to be confirmed.
Having analyzed 10 studies on the benefits of taurine for athletes, the authors of the review concluded that taking an additional supplement with 1-6 grams of taurine can increase strength and endurance.
However, the studies themselves that examined the influence of taurine on muscle strength and endurance do not look very convincing: they were either too short, or involved a small number of people, or taurine was studied as part of sports drinks – which can mean that the effect may be related not to taurine, but to caffeine.
In the end, experts from the Australian Sports Commission and other reputable sports organizations do not include cysteine supplements on the list of beneficial supplements for athletes, as more quality research is needed to demonstrate their benefits. People who eat enough varied protein-rich foods are better off getting this amino acid with food.
Cittrulline
Citrulline is a non-protein amino acid that serves a crucial role in the synthesis of arginine, which facilitates muscle blood flow and creatine production for muscle energy. It can be found in a variety of foods including dairy products, fish, eggs, beans, peanuts, onions, garlic, and notably, watermelon. There are no established daily intake recommendations for non-essential amino acids such as citrulline. Athletes use citrulline to enhance their physical performance.
Evidence of the effectiveness of citrulline. There is an effect from citrulline – but it is very weak, approximately the same as arginine.
To illustrate, individuals engaged in physical activities who consumed a drink containing 6-8 grams of citrulline 40-60 minutes prior to their training were able to perform three additional repetitions in a single set compared to those who ingested a placebo drink. Similarly, for runners who consumed a drink containing 3 grams of citrulline three hours before a race, their track time was only 7 seconds longer than those who consumed a placebo.
In summary, experts from the Australian Sports Commission and other authoritative sports organizations do not include citrulline supplements in the list of beneficial supplements for athletes, as more quality research is needed to demonstrate their benefits. For people who eat a varied protein diet, it is more beneficial to obtain this amino acid with food.
Phenylalanine and Tyrosine
Phenylalanine and Tyrosine are aromatic amino acids that belong to a subgroup of amino acids. Phenylalanine is an essential amino acid, whereas Tyrosine is a replaceable amino acid that can be obtained from food.
These two amino acids play crucial roles in protein synthesis and are also involved in the production of the neurotransmitter dopamine. Dopamine has multiple functions, including appetite suppression and stress reduction, especially during intense physical activity. Moreover, Phenylalanine also participates in the conversion of fats into energy.
Various food sources contain Phenylalanine and Tyrosine, including red and white meat, fish, seafood, eggs, cheese, cottage cheese, oatmeal, peanuts, sunflower seeds, almonds, and bananas.
The daily recommended allowance for both amino acids is calculated together, with the recommended intake being 25 mg/kg for adults.
Phenylalanine and Tyrosine are commonly used in sports supplements. While the two amino acids have similar physiological effects, supplements made from them are marketed differently. Phenylalanine-based supplements are promoted as fat burners, whereas Tyrosine-based supplements are believed to replenish dopamine reserves that are depleted during workouts, thus enhancing performance and endurance.
There is limited evidence regarding the effectiveness of phenylalanine supplements for weight loss, with only a small number of participants in the studies conducted. For instance, a study examining the appetite-suppressing effects of supplements containing phenylalanine and tyrosine involved only 17 people, while another study investigating the potential fat-burning effects of taking 3 grams of phenylalanine before exercise had only six volunteers.
Therefore, it is uncertain whether phenylalanine is effective as a fat burner, and reputable sports organizations are unlikely to recommend it as a supplement for athletes in the near future. Although phenylalanine is an essential amino acid, individuals who consume a balanced diet typically do not experience a deficiency and can obtain it through their food.
Similarly, studies on the effects of tyrosine on endurance and other sports performance indicators have shown no significant difference between taking the amino acid and a placebo. For example, a study involving ten men who received 150 mg/kg of tyrosine demonstrated the same treadmill performance and muscle strength as the ten participants who received a placebo.
Therefore, authoritative sports organizations such as the Australian Sports Commission do not recommend athletes to take tyrosine supplements. Instead, individuals who consume a varied, protein-rich diet can obtain sufficient amounts of tyrosine through their food.
Amino acid table for athletes: the most important things
| Amino Acid | Roles in the Body | Found in | Daily Requirement | Supplement Beneficial? | How to Take |
|---|---|---|---|---|---|
| BCAA (Branched Chain Amino Acids) | Stimulates muscle growth | Meat, dairy products, legume mix, nuts, grains and seeds | Leucine: 39 mg/kg, Isoleucine: 20 mg/kg, Valine: 26 mg/kg | No | — |
| Beta-alanine | Needed for the synthesis of carnosine | Animal foods | — | Yes | 6.4 g/day |
| Arginine | Increases the level of growth hormone and creatine | Poultry, fish, red meat, dairy products, nuts, seeds | — | No | — |
| D-Aspartic Acid | Increases testosterone and growth hormone levels | Oysters, red meat, dairy products, sprouted seeds, oatmeal, soy | — | No | — |
| Histidine | Synthesis of carnosine | Any protein-rich foods | 10 mg/kg | Only in conjunction with beta-alanine | Beta-alanine: histidine 2:1 |
| Glycine | Synthesis of glutathione and creatine | Any protein-rich foods | — | No | — |
| Glutamine | Facilitates adaptation to training | Dairy products and other protein-rich foods | 10.4 mg/kg | No | — |
| Threonine | Synthesis of glutathione | Red and white meat, fish and seafood, tofu, dairy products, seeds, nuts and legumes | 15 mg/kg | No | — |
| Cysteine | Synthesis of glutathione and taurine | Chicken eggs, fish, seeds, nuts, whole grain products | 4.1 mg/kg | No | — |
| Citulline | Synthesis of arginine | Watermelon, dairy products, fish, eggs, beans, peanuts, onions and garlic | — | No | — |
| Phenylalanine and Tyrosine | Synthesis of dopamine and conversion of fats to energy | Red and white meat, fish and seafood, eggs, cheese, cottage cheese, oatmeal, peanuts, seeds, almonds, bananas | 25 mg/kg | No | — |
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