Arginine in sports (and bodybuilding in particular) is one of the most popular types of sports nutrition.
It is taken to stimulate the natural production of growth hormone, as well as to dilate blood vessels and enhance the effects of creatine. This is an undeniable advantage for those who engage in sports… if that is the case.
If you study popular resources that write notes about the benefits of various types of sports nutrition concerning arginine (on the first page of the search results, bodybuilding.com and flexonline.com were found), it becomes embarrassing that you still do not use arginine: the list of benefits is impressive.
Even more surprising is the convincing and uncompromising nature of these platforms’ assertions: in all matters where scientists tactfully avoid unequivocal statements due to a very weak scientific basis, the authors of internet resources are absolutely confident.
The well-known “guru” in understanding the merits of sports nutrition in bodybuilding, Jim Stoppani, for example, who plays the role of an expert on both mentioned platforms, almost always appeals to scientific research, but very rarely provides references to them…
For him, it is quite normal to express it like this: “one study in 2006 showed…“. Dear Jim, in 2006, scientists studied millions of different things…
In this article, we will talk about what arginine is and what it is needed for in bodybuilding and other sports, about its benefits and harms.
And we will do all this in a comparative style: we will compare information from popular sites and scientific sources.
A similar approach is recommended in researching the benefits or uselessness of all sports supplements, pharmacological agents, and diets.
Popular internet resources on bodybuilding are characterized by an affirmative narrative style about the benefits of different types of sports nutrition even where scientists say “unlikely.” This also applies to the benefits of arginine in sports.
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What is arginine and what is it needed for?
Arginine is a conditionally essential amino acid (one of 22) that participates in numerous biological processes in our body.
Let us remind you that amino acids are what proteins are made of.
During digestion, proteins from food break down to the level of amino acids, which, entering the blood, serve as a substrate for creating various substances needed by the body (muscle proteins, hormones, enzymes, etc.).
Arginine performs the following functions in the body 18:
- hormone secretion (it stimulates the release of growth hormone with known anabolic potential);
- removal of toxic substances from the body (detoxification of ammonia, which is formed during protein metabolism);
- functioning of the immune system;
- protein synthesis.
In natural products, arginine is found in sufficiently large quantities in red meat, poultry, fish, and dairy products.
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What is the purpose of arginine in sports and bodybuilding?
In medicine, arginine is sometimes recommended for the treatment of erectile dysfunction (improving sexual function), lowering blood pressure, alleviating symptoms of angina (chest pain in the heart area), and leg pain due to poor blood circulation in the limbs.
In sports, and especially in bodybuilding, arginine has recently become popular, and it is taken because it is believed that it:
- increases the natural level of growth hormone;
- enhances the release of nitric oxide;
- participates in the synthesis of creatine;
- participates in the synthesis of proteins, including muscle proteins;
- increases endurance;
- is beneficial for weight loss.
Let’s take a closer look at these properties.
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Arginine in sports: benefits, harms, uselessness… Scientific facts
At the very beginning, we lightly criticized respected internet resources with a million audiences. Perhaps this is not entirely tactful. But there are grounds for this.
Below, based on scientific research, we will show why affirmative and unequivocal answers to the question “what is arginine and what is it needed for in bodybuilding?” are incorrect, although, without a doubt, they sell well…
1 Arginine and growth hormone
flexonline & Jim Stoppani 16: “Bodybuilders take arginine to increase natural growth hormone production. Arginine stimulates the production of growth hormone“.
It is a well-known fact that taking arginine stimulates the natural production of growth hormone 3,4. This is related to the suppression of the production of another hormone, somatostatin 5, which inhibits the secretion of growth hormone.
In various studies, the dose of arginine that causes such a reaction ranged from 12 to 30 g. However, clinical studies are very contradictory.
Clinical studies on the effectiveness of arginine for increasing growth hormone are very contradictory
When arginine (dose 1.2 g) was taken together with another amino acid, lysine (1.2 g), by young men, it led to a spike in growth hormone levels by 8 times at the 90th minute 6.
At the same time, when arginine and lysine were taken separately, growth hormone levels did not change.
In another study, when arginine and lysine were taken simultaneously, growth hormone levels increased by 2.7 times in the blood of athletes 7. In this same study, by the way, an increase in growth hormone levels was shown as a result of training (and without taking arginine) – another known natural factor for its increase.
Here 8, scientists fed endurance-trained athletes (marathon runners) 15 g of arginine aspartate for 14 days before the marathon.
On the day of the marathon, they measured growth hormone levels in the blood before the race, after 31 km, at its completion, and after recovery over 2 hours.
The result: growth hormone levels were significantly above normal during the race, considering its increase with physical activity. However, it was also found that the concentrations of other amino acids in the blood significantly decreased.
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The correct balance of amino acids is crucial for the biochemical processes in the body, including muscle protein synthesis and hormone production (not just growth hormone). A deficiency of even one of them (especially essential ones) can have consequences.
Based on this fact, scientists concluded: “since the consequences of a significant increase in arginine levels in the blood are unclear, the practice of using a single amino acid in sports, in this case arginine, as an ergogenic aid, should be critically re-evaluated.”
Taking arginine in large doses increases growth hormone levels but significantly decreases levels of other amino acids in the blood
There are many studies (involving both athletes and regular physically active individuals) that demonstrate the lack of influence of arginine consumption on growth hormone levels.
When men (amateur bodybuilders) involved in a strength training program took 8 grams of arginine for 17 days, no changes in growth hormone concentration in the blood were recorded 9.
A negative result was also shown in an experiment involving male bodybuilders who took a sports supplement containing arginine and lysine (1.2 g of arginine and 1.2 g of lysine) in the manufacturer-recommended doses 10.
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Here 2 scientists note that despite the fact that “many athletes in bodybuilding take arginine before training believing in its ability to enhance the effect of natural growth hormone production known for its benefits for muscle mass gain, the body’s response to its intake is highly individual.”
There is also a rather sharp statement from the scientists:
“There is no study that confirms that oral intake of arginine before training enhances growth hormone production, nor does it lead to an increase in muscle mass or strength“
The scientists’ verdict: the intake of individual amino acids, including arginine, to stimulate growth hormone production is NOT recommended.
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2 Arginine and creatine
Another popular theory in bodybuilding is that if arginine and creatine are taken simultaneously, the effect of creatine is enhanced, as arginine is involved in the synthesis of creatine in the body.
Creatine is one of the few sports supplements whose effectiveness is confirmed by scientists. Its use allows for an increase in muscle strength, the size of muscle cells, and, consequently, muscle mass.
Creatine is especially beneficial in sports that require short bursts of powerful energy, such as sprinting, swimming, cycling, jumping, strength sports, and bodybuilding.
The question that interests us: does the simultaneous intake of arginine with creatine (either from food or from sports supplements) lead to an increase in athletic performance?
Scientists say – unlikely 1.
The best method for increasing creatine concentration in muscles is its intake in the form of supplements or appropriate foods.
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Scientists state that the intake of arginine does NOT affect the effectiveness of creatine
3 Arginine and nitric oxide (NO)
flexonline & Jim Stoppani 16: “The nitric oxide produced by arginine improves blood flow to the muscles, increases strength (as shown in 2006), enhances muscle mass growth and weight loss (as shown in 2007)“.
bodybuilding.com 17: “Due to arginine’s ability to dilate blood vessels (through nitric oxide), it can be beneficial for athletes and people with obesity to lower blood pressure“.
Arginine, when it enters the bloodstream, stimulates the production of nitric oxide (NO), and this property is most often used as an argument for its use in sports and bodybuilding.
What is so remarkable about nitric oxide?
Nitric oxide causes vasodilation 11. Dilated blood vessels mean better blood supply to organs and tissues, including muscles: they receive more nutrients and oxygen. This can positively affect endurance and other athletic performance indicators.
However, scientific studies indicate that despite the fact that the concentration of arginine in the blood significantly increases with its intake, it does not always influence nitric oxide 1. Let’s consider a few examples.
In one study, professional athletes (judokas) took 6 g of arginine for 3 days, and their physical condition was tested on a cycle ergometer 34.
Result: in the group that took arginine, its concentration in the blood was significantly higher before, during, and after training. The concentration of nitric oxide was significantly above normal levels during and immediately after training in both groups.
There was no difference in the concentration of nitric oxide in the blood, markers of muscle fatigue (lactic acid and ammonia), as well as strength indicators during training between the groups.
Conclusion of the researchers: short-term intake of arginine as a supplement does not have any effect on increasing nitric oxide NO in the blood, reducing fatigue markers, or improving strength indicators in trained athletes.
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In another study, it was shown that despite the fact that after taking 10 g of arginine its concentration in the blood increased by 300%, no changes in nitric oxide concentration were observed, nor changes in blood flow in the muscles…
The researchers concluded that oral intake of arginine has no effect on the level of nitric oxide in the blood or on muscle mass growth in young people 26.
In this scientific review 25, researchers analyzed all available studies regarding the effect of arginine supplementation on nitric oxide. They note that only in half of them was any effect shown, while in the other half, none was observed.
It is commonly believed that taking arginine as a supplement stimulates the production of nitric oxide in the blood, which dilates blood vessels, improving muscle blood flow. Scientific studies indicate that this is not always the case.
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4 Arginine and Sports: Impact on Athletic Performance
The answer to the question of the benefits of arginine in sports is already clear, as it is determined by the influence of this supplement on important indicators for athletes – growth hormone, nitric oxide, and creatine, which we have already discussed.
Nevertheless, a few additional facts.
flexonline & Jim Stoppani 16: “The nitric oxide produced by arginine improves blood flow to the muscles, increases strength (as shown in 2006), and enhances muscle mass growth and fat loss (as shown in 2007)“.
Considering the attributed properties of arginine, it seems quite likely that its use in sports should positively affect athletic performance and body composition.
However, there is very little evidence that this is the case. The available data is quite contradictory 1.
In an experiment involving professional male wrestlers who took 1.5 g of arginine for every 10 kg of body weight and participated in an endurance training program, it was shown that there were no significant differences in blood lactate concentration (a marker of fatigue), oxygen consumption levels, or heart rate compared to those who did not take arginine.
However, the duration of the workout to exhaustion was longer in the group that took arginine. The researchers concluded: the consumption of L-arginine may be beneficial for increasing endurance in men, although the mechanism is not fully understood 15.
Conversely, when untrained men took 3 grams of arginine per day for 15 days and then underwent a muscle fatigue test during strength training, a significant reduction in muscle fatigue was noted 33.
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In the aforementioned study of bodybuilders who took 8 g of arginine per day, no positive effect was noted either in the changes in muscle function indicators (biceps and quadriceps) or in the ratio of fat to muscle mass 9.
Scientists cite several reasons why arginine consumption may not yield results. Its effectiveness is determined by:
- training level: trained athletes have a weaker response to arginine;
- gender;
- age;
- diet;
- method of administration (oral or injections).
Arginine injections always increase growth hormone levels, while oral consumption in large doses sufficient to increase growth hormone is likely to lead to side effects: stomach discomfort and diarrhea.
The intensity of training is called the main factor determining the secretion of growth hormone.
In addition to studies on healthy individuals, there are several experiments involving people with heart diseases 12-14.
In one of them, patients with chronic heart failure took 9 grams of L-arginine for 7 days and trained. The conclusion of the scientists: arginine intake by patients with chronic heart failure in moderate doses increases training duration 12.
In patients who underwent treatment for myocardial infarction, scientists also noted a positive effect on training capacity after consuming 3 g of arginine for just 3 days 13.
Here, researchers 14 showed a significant increase in oxygen consumption and physical performance during cardio exercises after taking 1.5 g of arginine per 10 kg of body weight for 7 days. The reason cited is the same nitric oxide, which dilates blood vessels and improves blood supply.
The existing scientific data regarding the actual benefits of arginine intake in sports is very contradictory: in some experiments, scientists observe changes in important indicators for athletes, while in others, they do not. The level of training likely plays a role.
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5 Arginine for weight loss
Arginine is involved in numerous processes of fat, glucose, and protein metabolism, which are somehow related to fat burning. It enhances lipolysis (fat breakdown) and stimulates fatty acid oxidation 27.
Multiple studies on animals (pigs, rats) show that adding arginine to feed positively affects weight loss (body fat percentage) and increases muscle mass 28,29.
Research on humans also looks quite promising.
For example, in an experiment involving 20 women aged 18-40 with obesity, who took 3 g of L-arginine three times a day for 12 weeks, a reduction in waist circumference and weight was observed. The conclusion of the scientists: L-arginine may be beneficial for weight loss 30.
A similar conclusion about the great potential of arginine for weight loss in men and women is made by scientists here 31 and here 32, based on the analysis of existing scientific data and the mechanism of action of arginine.
However, it is important to make a significant caveat.
No matter how promising the scientists’ forecasts regarding the benefits of any supplements (in this case, arginine) for weight loss or muscle gain may seem, it would be naive to believe that the desired goal can be achieved faster by taking this supplement in large doses, and the more, the better.
Remember: excess arginine leads to the suppression of levels of other amino acids in the blood, each of which has equally important functions in the body.
No fat burner or weight loss product will ever solve the problem of poor nutrition. It is a mistake to think that one can simultaneously eat food that is enjoyable but promotes obesity, and use scientifically proven effective supplements for weight loss to correct its negative impact.
The effect of any effective fat burners is a couple of hundred calories, equivalent to a piece of bread/roll/a few cookies.
Scientific studies confirm the effectiveness of arginine for weight loss in experiments on animals and humans. But remember, no supplement will ever solve the problems of poor nutrition.
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6 Arginine and Endurance
Arginine reduces the amount of metabolic byproducts – lactic acid and ammonia in the blood – which are markers of muscle fatigue 22.
On the other hand, improved blood supply resulting from the dilation of blood vessels when consuming arginine ensures more effective delivery of nutrients to the muscles (macro- and micronutrients, oxygen), which should also positively affect endurance.
As shown, these properties of arginine are not always confirmed.
Therefore, it is impossible to definitively state that arginine is beneficial for endurance.
Theoretically, arginine should be a good sports nutrition supplement for increasing endurance. However, its properties do not have unequivocal scientific confirmation due to the contradictory nature of research on its influence on blood nitric oxide levels and the concentration of muscle fatigue markers.
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Natural sources of arginine
Good sources of arginine are protein-rich foods 20:
- poultry;
- fish;
- eggs and egg protein;
- pork;
- nuts and seeds (pumpkin seeds, peanuts, walnuts, hazelnuts);
- legumes (lentils, chickpeas);
- chocolate (more in dark chocolate);
- zucchini, oatmeal, wheat.
For exact values of arginine content in foods, see the material Table of arginine content in foods.
Harm of arginine and side effects
L-arginine is considered a relatively safe type of sports nutrition.
The harm of arginine in case of overdose may manifest in the following side effects 22:
- abdominal pain;
- bloating;
- diarrhea;
- gout;
- allergy;
- inflammation of the respiratory tract;
- worsening of asthma;
- low blood pressure.
Additionally, L-arginine may worsen herpes symptoms, as the herpes virus reproduces more effectively in its presence and requires arginine for survival 22,23.
Caution should be exercised when taking arginine, especially for those with low blood pressure: vasodilation may further lower it.
Arginine is considered a safe sports supplement. The harm of arginine in case of overdose most often manifests in digestive side effects. Its intake may worsen herpes symptoms.
Conclusion
The role of arginine in creatine synthesis, its ability to influence nitric oxide production, which dilates blood vessels, and the natural production of growth hormone are the basis for its popularity in bodybuilding and other sports.
However, the effectiveness of additional arginine intake in sports (bodybuilding) for healthy athletes has very weak scientific confirmation.
Scientists suggest that the body’s response to arginine as a supplement may be individual and is determined by the level of training (the more trained the athlete, the weaker the effect), gender, age, as well as the form of intake (oral or injection; oral supplements are very ineffective).
