Amino acids perform a huge number of functions in the body and are, in a sense, the molecules that govern its functioning.
They are used to build organs and tissues (including muscles), hormones, and enzymes; they regulate metabolic reactions, provide immunity, and even influence mood and feelings of fatigue.
The importance of individual amino acids is often manipulated by sports nutrition manufacturers and their “experts,” recommending their intake in the form of supplements.
However, in their action, amino acids are very similar to medications: contrary to our desire to correct something specific with their help, they have a complex effect on the body, increasing the risk of side effects.
Today, many scientists question the practice of taking individual amino acids.
Methionine is one of the amino acids that is often recommended for use in sports and bodybuilding to stimulate muscle growth.
The basis for this is its anabolic properties: it directly participates in the construction of muscle tissue, not only as a structural component but also manages the very process of protein synthesis.
In this article, we have gathered scientists’ opinions on the benefits and harms of methionine based on scientific research and tried to understand how justified its use is in sports and bodybuilding, how to take it correctly, and whether it is worth it, as well as what possible side effects may arise.
Main thoughts:
Methionine is the only essential amino acid containing sulfur that must be obtained from food.
Restricting methionine in the diet leads to the death of cancer cells
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What is methionine?
Protein is made up of amino acids. During digestion, the protein molecule is broken down into its components, amino acids, which are then used to create proteins that make up the structure of organs and tissues (including muscles), hormones, enzymes, etc.
In addition to their structural role, some amino acids perform other specific functions that are important for normal metabolic processes.
Methionine is one of the 8 essential amino acids and the only one that contains sulfur. It is involved in the creation of several important molecules necessary for the normal functioning of the body.
Its essentiality implies that it must be present in the diet, and the sulfur content determines both its beneficial properties and potential harm to health when consumed in excessive amounts.
Methionine is naturally found in large quantities in meat, fish, and dairy products, and those who consume these foods are likely to obtain it in sufficient amounts.
Methionine is the only essential amino acid that contains sulfur and must be obtained from food
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Benefits of methionine. Functions of methionine in the human body
Methionine is involved in the creation of several important molecules in the human body 2:
- SAM (S-adenosylmethionine);
- cysteine amino acids;
- taurine amino acids;
- the antioxidant glutathione.
The substance abbreviated as SAM (S-adenosylmethionine) is involved in the synthesis of creatine in the body, known for its ergogenic properties in bodybuilding, neurotransmitters (serotonin, dopamine, melatonin), and is important for supporting immune function, the mechanism of reproduction of hereditary information via DNA, and many other vital functions 26.
Glutathione is one of the main antioxidants in our body; it plays a very important role in protecting cells from oxidative processes, synthesizing DNA and proteins, combating aging processes, and supporting immune function 27.
Taurine is known as an ingredient in energy drinks and has certain health and sports benefits. It affects endurance and recovery speed in sports and is beneficial for the health of the eyes, brain, liver, and heart.
The amino acid cysteine is synthesized from methionine and plays an important role in skin formation and is a powerful antioxidant.
Sulfur in methionine plays an important role in the production of cartilage, which supports joint health, and also explains its antioxidant properties: its presence in the body increases acidity, which helps prevent urinary tract infections, in particular 3. However, increased acidity also has negative side effects (see below).
According to scientific studies, healthy cartilage contains three times more sulfur than that of individuals suffering from arthritis (joint disease) 7.
Sulfur cannot be taken in tablet form. Methionine is a good source of it.
Methionine is a glycogenic amino acid. This means that when necessary, glucose and glycogen—sources of energy—can be created from it.
Methionine is directly involved in the creation of proteins within the body, from which organs, tissues, and muscles are built.
The health of hair and nails directly depends on its adequate presence in the diet, as sulfur helps form stronger structural bonds 8.
The benefits of methionine for the human body are largely explained by its sulfur content: it supports protein synthesis in the body, the health of hair, nails, and joints, and possesses antioxidant properties.
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The Benefits of Methionine in Bodybuilding for Muscle Mass Gain
Experiments on laboratory animals have shown that a deficiency of methionine in the diet leads to slowed growth and smaller sizes in adult individuals 25. This clearly indicates the importance of methionine in bodybuilding for muscle mass gain.
The use of methionine in bodybuilding is justified by its anabolic properties, i.e., its involvement in the muscle growth process.
Together with another sulfur-containing amino acid, cysteine, which is non-essential and synthesized in the body from methionine, they play a critically important role in protein synthesis in the human body: not only are they structural components of proteins, but they also initiate the very process of their synthesis 26.
The amino acid taurine, known for its content in energy drinks, is also created from methionine. The reason for its addition to energy drinks is a scientific secret, however, research indicates its possible benefits for increasing endurance and recovery speed in sports 26.
So, this is what concerns the benefits of methionine in bodybuilding.
Does the information provided mean that the more of this amino acid in the diet, the faster one can gain muscle mass?
No. On the contrary.
Scientific studies indicate that excessively high doses of methionine can hinder muscle mass growth and even promote its breakdown (catabolism). More on this below.
Methionine in bodybuilding is one of the most important amino acids for gaining muscle mass. However, consuming it in large amounts can hinder mass gain and even stimulate its breakdown (catabolism)
Is methionine beneficial for weight loss?
There is no basis to believe that the amino acid methionine in supplement form can be beneficial for weight loss.
For weight loss, protein in food (fish, eggs, cottage cheese, meat, legumes) is beneficial, as it has a high satiety index and possesses a thermogenic effect, i.e., it requires more energy for digestion.
The thermogenic effect is characteristic only for whole protein molecules. Its essence lies in the breakdown of the protein molecule into individual amino acids during digestion, which requires additional energy expenditure.
When free amino acids, including methionine, are consumed, this component of energy expenditure is excluded.
There is no basis to believe that taking methionine in supplement form can be beneficial for weight loss
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In which products is methionine found?
Methionine is found in large quantities in animal products. The best sources are fish, eggs, and meat.
Especially high levels of methionine are found in egg whites: about 8% of the total amino acid content in them is accounted for by methionine and cysteine – two sulfur-containing amino acids 29.
For chicken, this value is 5%, and for dairy products, it is 4%.
In plant products, the amount of methionine is significantly lower.
The table below shows a list of foods that are richest in methionine 29.
| Table of methionine content in foods (per 100 g) | |
|---|---|
| Egg white powder | 3204 mg |
| Atlantic tuna, dried | 1859 mg |
| Sesame seeds, flour | 1656 mg |
| Whole egg, dried | 1557 mg |
| Soy protein isolate | 1250 mg |
| Spirulina seaweed, dried | 1149 mg |
| Parmesan cheese | 1114 mg |
| Sunflower seeds, flour | 1043 mg |
| Brazil nut | 1008 mg |
| Chicken breast | 968 mg |
| Lean beef | 925 mg |
| Canned salmon | 910 mg |
| Non-fat dry milk | 907 mg |
| Turkey | 893 mg |
| Pork | 854 mg |
| Egg yolk, dried | 849 mg |
| Watermelon seeds (kernels), dried | 834 mg |
| Soy protein concentrate | 814 mg |
| Pumpkin and squash seeds | 740 mg |
| Goose eggs, fresh | 624 mg |
| mozzarella cheese | 603 mg |
The content of methionine is significantly higher in animal products than in plant ones. Eggs, fish, and red meat are particularly rich in it.
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How to take methionine, instructions for use
The recommended dose of methionine is 10 mg/kg of body weight per day. For a person weighing 80 kg, this corresponds to approximately 0.8 g per day 9.
When calculating the dose of methionine, it is necessary to consider its content in natural products and sports nutrition products.
However, as noted at the beginning, many modern scientists criticize the practice of consuming individual amino acids in the form of dietary supplements.
Why? Just a few examples.
When consuming large doses of any one amino acid, the levels of others may be suppressed, as happens in the case of arginine.
Also in the material about the opinions of doctors and scientists on the benefits and harms of consuming amino acids or protein it is noted that the process of protein breakdown itself is very important, accompanied by a whole series of chemical reactions that have colossal significance.
But, as always, the choice is yours.
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Indications for the use of methionine
Methionine is NOT recommended to be taken without consulting a doctor or dietitian.
It is important to understand that individual amino acids are comparable in their action to medicinal drugs. This means that their intake is indicated only in certain cases.
For example, an indication for the use of methionine is the treatment of symptoms of poisoning with the drug paracetamol 1, which is used as a pain reliever.
Self-administration of methionine is contraindicated, as excessive doses increase the risk of harm to health: certain forms of cancer, the formation of kidney stones, and other consequences related to increased acidity in the body.
All of this is also true regarding the consumption of methionine in sports and bodybuilding for gaining muscle mass.
Methionine is not recommended to be taken without consulting a doctor and dietitian. Large doses may increase the risk of harm to human health.
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The benefits of limiting methionine in the diet. The influence of methionine on lifespan and aging
One of the theories of aging is DNA damage as a result of oxidative stress, caused by reactive oxygen species 5.
All long-lived mammals have low levels of such damage in their bodies.
According to this theory, reducing the amount of protein in the diet, and especially the amino acid methionine, slows down aging and increases lifespan. This has been proven in experiments on laboratory animals 5,6,17.
Limiting methionine increases the lifespan of animals by more than 40% (!), while also more effectively burning fats in the body and improving health indicators, including body composition (the ratio of fat mass to muscle) and insulin sensitivity 25.
At the same time, scientists talk about the absence of negative side effects dangerous to human health when limiting the amount of methionine in the diet 25, except for slowing down growth rate. This may be a problem for a growing organism, but not for an adult, except for.. representatives of bodybuilding.
Thus, in bodybuilding the effect of methionine is twofold: on one hand, as an anabolic agent, it is necessary for muscle growth, as it participates in the synthesis of muscle proteins; on the other hand, if there is too much of it, muscles will not grow.
While in sports and bodybuilding methionine is recommended to be taken in large doses, scientific research emphasizes the health benefits of its limitation
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Harm of methionine and possible side effects
Methionine is considered a relatively safe dietary supplement; however, scientific research on its harm to human health is contradictory.
Some of them indicate the safety of its use even at doses three times higher than recommended 10.
Effect of methionine on acidity
Excessive consumption of methionine leads to a change in the acid-base balance in the body towards increased acidity. This effect is due to the sulfur in its composition.
What are the dangers of increased acidity?
Increased acidity is one of the main reasons for the harm of protein to human health: it increases the risk of kidney stones and cancer, and decreases bone strength.
Moreover, this primarily concerns animal-derived proteins, which contain more methionine than plant-based ones.
Also – and this is particularly important in bodybuilding – increased acidity in the body is a factor that hinders muscle protein synthesis and promotes muscle breakdown, which manifests as a negative nitrogen balance and is clearly an obstacle to gaining muscle mass in bodybuilding 11-13.
Nitrogen balance is a parameter that reflects whether there is enough protein in the diet to support muscle growth.
Experiments with varying amounts of methionine in the diet show that the cause of negative nitrogen balance is indeed the dose of methionine: the higher it is, the more negative the nitrogen balance and the less favorable the conditions for muscle mass growth 14.
The harm of methionine manifests as increased acidity in the body when consumed in large doses, which increases the risk of cancer, kidney stone formation, and also hinders muscle mass gain in bodybuilding
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Methionine and Schizophrenia
Large doses of methionine may exacerbate the course of schizophrenia 15.
Some studies have shown that doses of methionine exceeding 20 g per day can cause clouding of consciousness, disorientation, delusions, increased activity or lethargy, and other symptoms characteristic of this condition 16.
Methionine and Atherosclerosis
Methionine in large amounts may increase the risk of atherosclerosis (the formation of blood clots in blood vessels). The cause of this is said to be its metabolic product – homocysteine.
Factors contributing to the formation of homocysteine include a deficiency of B vitamins (folate, vitamin B12, and B6), as well as certain metabolic disorders 1,10.
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Methionine and Cancer
Scientific research indicates a close relationship between the amount of methionine in the diet and the risk of developing cancer 18.
Most cancer cells require methionine for growth. While healthy cells can survive without it, cancerous cells cannot.
As a carcinogen, methionine acts through several mechanisms.
Firstly, it is necessary for protein synthesis – the basis for cell growth, including cancer cells.
Secondly, methionine is converted in the body into so-called polyamines – substances involved in the cell proliferation process, which are found in high concentrations in tumors and are factors in their growth 19,20.
Thirdly, methionine stimulates the release of insulin-like growth factor IGF-1, under the influence of which not only organs and tissues grow, but also tumors.
Limiting methionine in the diet significantly reduces the risk of cancer and leads to selective death of cancer cells, while healthy cells remain unharmed 18,21-23. It also halts the growth of metastases.
Conclusion of the scientists: “The results of our studies explain the health benefits of calorie restriction, intermittent fasting, and vegetarian diets, which help reduce the rate of protein synthesis in the body.”
Limiting methionine in the diet leads to the death of cancer cells
Interestingly, scientists note that both calorie restriction and a diet with normal caloric intake but limited methionine content are equally beneficial as means to combat cancer 18.
Since plant-based proteins contain less methionine than animal proteins, this explains the advantage of a plant-based diet for preventing and combating cancer 28.
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