Dietary supplements that come in the form of tablets, capsules, or powders containing a particular concoction of amino acids, usually claimed by the manufacturers to have special properties. Most amino acid supplements are sold as anabolic agents to help in body-building; arginine and ornithine, for example, are frequently promoted as ‘natural steroids'. Since amino acids are the building blocks of protein, the main component of muscle, many people believe that just by taking extra amino acids they can develop larger muscles. However, a muscle grows only in response to extra physical demands placed on it. Excess amino acids not needed for growth or repair of body tissues are broken down and excreted as urea, converted into glucose and used as an energy source, or converted to body fat. Amino acid supplements may be beneficial when there is a natural stimulus to increase muscle bulk, for example, during the initial stages of training. There is little support for the claims that amino acid supplements improve strength, power, muscle growth, or work capacity. Most sports nutritionists agree that a normal, healthy person eating a well-balanced diet need never consume amino acids supplements (see also sports nutrition). Overconsumption may lead to health risks. Many amino acids are toxic when taken in excess.
Subjects: Sports and Exercise Medicine.