Protein supplements are used mainly by bodybuilders and other athletes looking to maximize their muscle growth and prevent muscle loss. This glossary covers common terms relevant to protein supplementation and muscle building.
Amino Acid
Amino acids are organic compounds that are the building blocks of proteins. Although the body can produce some amino acids naturally, there are nine essential amino acids that must come from dietary sources.
Branched-Chain Amino Acid
This term is used to refer to three specific essential amino acids – leucine, isoleucine, and valine – that are grouped for their similar branching structure and particular importance to muscle building. BCAAs are advertised as a must-have resistance training supplement, despite the fact that they are present in sufficient quantities in protein-containing foods.
Fast Protein
A source of protein that is digested quickly and easily, leading to a rapid rise in blood amino acid levels and subsequent muscle protein synthesis. Fast protein is believed to be ideal to consume before or after resistance training because the muscles may benefit from fast repair. Fast protein is synonymous with whey protein because it leads to the fastest and largest acute (up to 3 hours) spike in muscle protein synthesis.
Leucine
Leucine is a BCAA and the only amino acid known to directly stimulate muscle protein synthesis and potentially reduce muscle protein breakdown. Because of this, it is given special importance in the realm of muscle building. However, supplementing isolated leucine or other BCAAs is generally unnecessary because of its presence in foods and protein powders.
Muscle Protein Breakdown
The breakdown of protein in muscle tissue, which ultimately promotes muscle loss. Muscle protein breakdown can increase when protein consumption is insufficient and after strenuous exercise.
Muscle Protein Synthesis
The production of protein in muscle tissue, which ultimately promotes muscle growth. Muscle protein synthesis can be increased by upping nutrient (amino acid) availability through protein consumption and by undergoing resistance training.
Net Protein Balance
The relationship between the opposing processes of muscle protein breakdown (MPB) and muscle protein synthesis (MPS). If these processes are occurring at equal rates, muscle tissue remains the same; if breakdown is greater than synthesis, muscle tissue is lost; if synthesis is higher, muscle tissue is gained. In healthy, non-exercising individuals under the age of 40 this balance tends to remain neutral.
Protein
Proteins are biological molecules made of chains of amino acids. The body uses amino acids to produce its own proteins, which act as structural components of muscle and other tissues, and participate in a wide range of essential processes that include enzyme function, cell growth, and cell signalling.
Protein Concentrate
A form of supplemental protein powder made from a specific source, which contains 70-80% protein content. Protein concentrates are the most popular proteins supplements on the market.
Protein Isolate
A purified version of a protein concentrate powder that contains 90% or more protein.
Protein Quality
This metric helps determine how effectively protein from a given source is used by the body though rating its essential amino acid composition, digestibility, and bioavailability. There are currently four accepted metrics of protein quality: protein efficiency ratio (PER), biological value (BV), net protein utilization (NPU), and protein digestibility corrected amino acid score (PDCAAS).
Resistance Training
Also known as strength training, this is a type of exercise that uses resistance – an opposing force – to increase muscle size and strength. Weight lifting is the most common type of resistance training, but it is also possible to use one’s own body weight as resistance. Resistance training requires increased caloric and specifically protein consumption to maximize gains in muscle mass.
Sarcopenia
The gradual loss of muscle tissue caused by aging. Sarcopenia is a serious health concern for older adults, and seems to be caused largely by a blunted response to protein intake.
Slow Protein
A source of protein that is digested slowly, leading to a steady, prolonged release of amino acids. Slow proteins are believed to be ideal to take during periods of prolonged fasting, such as prior to sleep, by helping promote continued MPS and mitigate MPB. Casein protein is synonymous with slow protein.
