Amino Acids – What Are They?
Amino acids are a class of biologically active organic molecules. They all have a basic structure for which they are named – the carbon backbone has a nitrogen-containing amino group at one end and an organic acid group at the other. Attached to this backbone is a side chain. The side chains are what give each amino acid its unique properties. There are hundreds of known amino acids.
Amino acids are best known as the building blocks of protein. The term "amino acids" is often used in specific reference to the 22 amino acids the human body uses to make protein, or the "proteinogenic" amino acids. These amino acids are linked in a specific order into chains called polypeptides, which then go on to form proteins, including muscle.
Of the 22 proteinogenic amino acids, 9 are classified as "essential" - this means that the body is unable to produce these so they must be obtained from outside sources like food or supplementation.
Amino Acids for Building Muscle
While all amino acids are essential for muscle building, some are more important than others.
The essential amino acids are probably the most important. When protein is made, amino acids are laid down in a specific order. If levels of particular amino acids are low, the protein-making apparatus will take longer to locate them, forcing protein synthesis to slow or stop. It is therefore important to maintain a good intake of essential amino acids to promote fast and efficient synthesis of muscle tissue. The 9 essential amino acids are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan and Valine (1).
There are a number of Amino acids that have specific muscle building properties. Leucine has been the subject of much research and it is known that this amino acid stimulates the body to synthesise muscle. It also helps the body to metabolise sugar more effectively by stimulating insulin release (2).
Glutamine is the most abundant amino acid in muscle protein. It carries nitrogen around the body, so has an effect on nitrogen balance, which determines whether the body is in an anabolic or catabolic state. After exercise, glutamine is lost from the muscles so it is very important to replenish this (3). Glutamine also enhances the immune system, which is important for anyone in serious training (4).
Amino Acids for Muscle Recovery
Recovery is everything in bodybuilding – it is the time when new muscle is formed. A good workout will leave you feeling sore and shaky but a quick recovery will get you back in the gym sooner, working harder, and continuing to make gains.
There is one group of amino acids synonymous with recovery, and these are the BCAAs, or Branched Chain Amino Acids. The BCAAs are Leucine, Isoleucine and Valine. Leucine has been previously discussed for its anabolic effect. Along with the muscle building effects of BCAAs, studies have shown that BCAA supplementation greatly reduces both inflammation and soreness after a workout (5).
Arginine is a nitric oxide (NO) booster commonly used in recovery. NO expands the blood vessels, resulting in greater blood flow to the muscles. It is popularly used during workouts to give a better pump and increase strength. Like BCAAs, Arginine could easily be included in the Muscle Building category, but it is also a great aid to recovery, allowing the delivery of more oxygen, nutrients and fuel to the recuperating muscles (6).
Amino Acids for Weight Loss
Increasingly, high protein intake is being linked to weight loss. Weight loss is a catabolic process, where body mass is lost. One of the goals of healthy weight loss is to burn fat, not muscle. Besides muscle being more useful than fat, muscle cells use more energy than fat cells. Having more muscle tissue therefore increases the body's metabolic rate, enhancing the efficiency of fat loss. In addition, protein is known to promote feelings of fullness, so a diet rich in protein, therefore amino acids, is a great way to shed excess fat. Some amino acids do possess specific properties that make them more important than others when it comes to shedding the kilos.
While not strictly an amino acid, carnitine is a dipeptide made up of the amino acids methionine and lysine. It is one of the oldest and best known nutritional supplements, and its main use is as a fat burner. Carnitine transports fatty acids into the mitochondria, the body's energy centre, where they are used for energy, enhancing fat metabolism (7)
Tyrosine and Phenylalanine are amino acid precursors to a group of hormones named catecholamines, which include adrenalin, noradrenalin and dopamine. Adrenalin and noradrenaline are important regulators of metabolism, and dopamine can play a role in modulating appetite – it is the neurotransmitter associated with feelings of fullness or satiety. These amino acids are often taken alongside appetite suppressants, as they may enhance the effects (8).
Amino Acids for Depression
Serotonin, often called "the happy chemical", is a neurotransmitter which is tied to mood. Low levels are thought to be associated with depression, and many anti-depressant medications work by increasing the amount of active serotonin in the brain. Tryptophan is the amino acid precursor to serotonin. It is possible that higher levels of this precursor amino acid will increase serotonin levels in the brain, lifting mood (9).
Tyrosine, as a noradrenalin precursor, is though to act in a similar fashion. Noradrenalin is widely held to be the secondary neurotransmitter affecting mood and depression after serotonin, and as a precursor, raised tyrosine levels can also raise noradrenalin levels, particularly where there is a deficiency (10). It is also known to play a role is supporting healthy sleep.
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