While plenty of research has been carried out on the importance of an adequate role of complete proteins, over the past several decades researchers have had a growing interest in the specific roles of protein building blocks, called amino acids, in overall health, metabolism, body composition, and sports performance.
Whether you have clients who have asked you about whether they should take an amino acid supplement or if you simply want to stay up-to-date with the latest sports nutrition research, we summarize the latest findings and consensus in a clear manner.
This article is a review of the evidence that examines if increased intakes of specific amino acids increase health, and it takes a close look at the evidence behind the claim that some amino acids can increase fat loss.
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Amino Acids: The Basics
Amino acids are the building blocks of proteins. If you think of a protein like a Lego house, each Lego would be an amino acid. There are twenty-two different amino acids, two of which have only recently been discovered.
Just like you can put legos together in different ways to design a house, store, ship, or fire station, there are several ways the twenty-two amino acids can come together in a sequence to build different protein structures like hormones, enzymes, immune cells, or muscle fibers.
Some of the amino acids can be made by the body from other components. These are called non-essential amino acids.
The non-essential amino acids are:
- Alanine
- Arginine
- Asparagine
- Aspartic acid
- Cysteine
- Glutamic acid
- Glutamine
- Glycine
- Proline
- Pyrrolysine
- Serine
- Tyrosine
There are ten (formerly nine) amino acids, however, that the body cannot make. These essential amino acids are made available to the body through the foods we eat. When you eat, digest, and absorb protein-containing foods, the body takes apart the proteins from the foods and uses the building blocks (amino acids) to finish building the proteins your body needs at that moment. The ten essential amino acids are:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Selenocysteine
- Threonine
- Tryptophan
- Valine
When foods contain all the essential amino acids, they are referred to as complete proteins. There is a common misconception that plant-based proteins do not provide all the essential amino acids. This is not true. While most plant-based sources of proteins are commonly missing one or two of the essential amino acids in significant quantities, other sources of plant proteins can provide the complement to those amino acids to provide complete proteins.
There is also a third group of amino acids called conditional amino acids, sometimes called conditionally-essential amino acids. These amino acids can generally be made by the body, except for in times of illness and stress. These are:
- Arginine
- Cysteine
- Glutamine
- Tyrosine
- Glycine
- Ornithine
- Proline
- Serine
BCAAs: A Special Type of Essential Amino Acid
Branched-chain amino acids (BCAAs) tend to be discussed a lot in research in regards to the role of amino acids in fat burning.
Branched-chain amino acids (or BCAAs for short) are a sub-group of essential amino acids. There are three BCAAs: valine, leucine, and isoleucine. They have been studied for decades for their role in therapeutic strategies for chronic renal failure and different types of physical trauma like burns and sepsis. Together, BCAAs make up about one-third of skeletal muscle protein, which is why there has been an increasing interest in understanding the role of BCAA supplementation in athletes.
Recently, research has focused on their role in treating metabolic disorders for modifying body composition and their role in boosting exercise performance. We’ll review this research in the next section.
Amino Acids, Exercise, and Muscle Building
Amino acid supplementation has been adopted by bodybuilders and athletes for generations as a way to maximize performance and muscle growth.
Below is a summary of the main research finding regarding the effectiveness of amino acid supplementation in promoting health.
- Supplementation of the diet of older adults with glucose intolerance with essential amino acids and arginine can help increase muscle mass, strength, and overall physical function.
- Older adults experience sarcopenia, which is a loss of muscle and strength over time. Supplementation in older adults with the BCAA leucine may help prevent, slow, and even reverse sarcopenia.
- Following resistance exercise, supplementation with the BCAA leucine together with carbohydrate and protein led to increased protein synthesis when compared to carbohydrate and protein supplementation without leucine.
- BCAA supplementation may slow the rate of degradation of protein during aerobic exercise.
- Supplementation with BCAA before exhaustive aerobic exercise, like running, can help to improve performance and reduce mental and physical fatigue by delaying the depletion of glycogen (the stored form of glucose). This seems to benefit people with lower fitness levels who are engaging in regular exercise.
- Supplementation with free leucine and protein and carbohydrate may increase muscle protein synthesis after resistance exercise.
- Amino acid and carbohydrate supplementation helped to reduce muscle damage and fatigue in athletes.
- A high intake of the amino acid methionine can be toxic.
- Supplementation with the amino acid arginine generally doesn’t have any impact on exercise performance or muscle growth.
The International Society of Sports Nutrition (ISSN) recognizes the essential role of protein in exercise performance and overall health. In fact, the ISSN recommends that athletes and people who engage in regular exercise training increase their protein intake from the recommended RDA of 0.8 grams per kilogram to up to 2.0 grams per kilogram.
In terms of whether one type of protein or amino acid is superior to another type for athletes, the ISSN states, “Under certain circumstances, specific amino acid supplements, such as branched-chain amino acids (BCAAs), may improve exercise performance and recovery from exercise.”
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Can Amino Acids Increase Fat Loss? What the Evidence Says
Sports nutrition experts generally accept that increased consumption of protein through the diet and supplemental protein, especially with BCAAs, can increase exercise performance and support muscle growth under special circumstances, and it can prevent some forms of sarcopenia.
While there is plenty of research on the role of general high-protein diets on fat loss and body composition in general, researchers, nutritionists, and athletes alike are interested in the role that specific amino acids might have in fat oxidation, commonly known as “fat burning.”
Here is the summary of the research:
- An increased complete protein intake through high-protein diets is associated with greater fat loss.
- BCAA supplementation (76% leucine), together with moderate calorie restriction has demonstrated significant losses of abdominal visceral fat, which is the type of fat that covers organs, high proportions of which are associated with type 2 diabetes and heart disease.
- Taking BCAAs to support weight loss in people with type 2 diabetes is controversial. In some studies, it was shown to improve glucose control, while in others, BCAA supplementation in obese people with type 2 diabetes showed a potential to increase insulin resistance. This is because, in general, body compositions higher in fat correlate with high levels of BCAAs, and recent studies suggest that BCAA may interfere with the oxidation of fatty acids, leading to insulin resistance.
- Circulating BCAAs in the blood are generally associated with a greater percentage of body fat in non-athletes.
- BCAA supplementation in resistance-trained athletes on a hypocaloric diet can maintain muscle mass and performance while losing fat mass.
Research shows that while a high-protein diet together with exercise is associated with fat loss, an increased intake of specific amino acids, namely BCAAs, for achieving fat loss is only effective in specific cases. More specifically, BCAA supplementation may boost fat loss while preserving muscle mass and supporting performance in trained athletes, but it isn’t effective for healthy non-athletes who want to lose weight or for treating obesity.
If you or a client think that they would benefit from increased protein or specific amino acid intake, you can work with them to see how to maximize protein intake through diet. If it is more cost-effective for them to take a supplement, if they are still having trouble meeting protein intake through diet alone, or if they want to supplement with specific BCAAs to take advantage of the benefits for athletes, they may consider supplementation. Make sure you talk to your client about what they should consider before deciding to take a supplement.
Main Takeaways
Protein intake is an essential part of a healthy lifestyle for athletes and non-athletes alike. Athletes who have specific performance or body composition goals may find benefits to increasing their intake of specific amino acids, specifically BCAAs.
It is generally accepted that increased BCAA intake through diet or through supplementation can help to improve muscle mass, performance, energy metabolism, and overall body composition in people who engage in regular moderate to vigorous exercise. However, there is no substantial support for BCAA supplementation use on its own as a weight-loss aid.
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