Also, a distinction is sometimes drawn between dietary and exercise supplements, while this method of classification is not followed by all those who use supplements. If a distinction does exist, dietary supplements are often defined as those supplements that aim to give the body more of the nutrients that it ought to get from diet, but isn't for whatever reason. Protein, meal replacement and amino acids (in smaller quantities) based supplements are usually considered to be dietary supplements. Exercise supplements, however, involve raising a particular nutrient level far beyond what is typically consumed by a human for the explicit purpose of experiencing a positive side effect when combined with weight training. Creatine is a good example of an exercise supplement in that, while it is found in the body naturally, users typically ingest far more than is usually needed in order to saturate their muscles and achieve a much greater muscle gaining benefit.
Bodybuilders often take a powdered form of protein, the essential building blocks for muscle. Protein powder is generally consumed immediately after exercising, or in place of a meal. Having sufficient protein intake allows for efficient growth and repair of muscle tissue.
- Whey protein is the most commonly used type of protein. It contains high levels of all the essential amino acids not produced by the human body, and is absorbed by the body very quickly.
- Casein protein is the richest in glutamine, an amino acid that aids in recovery, and has casomorphin which helps the body to absorb the amino acids over a long time.
- Soy protein contains all essential amino acids, and is an alternative protein for vegetarians. However, soybeans contain a type of phytoestrogen called isoflavones which have a weak estrogenic activity .
- Egg white protein is a lactose- and dairy-free protein.
Glutamine is the most abundant amino acid found in human muscle and is supplemented because supplement manufacturers claim the body's natural glutamine levels are depleted during anaerobic exercise. It is argued that supplementation by bodybuilders may be required as deficiency may lead to a weakened immune system and wasting of muscle tissue. It is sold as a micronized, instantly soluble powder.
Branched chain amino acids
Amino acids are the building blocks of protein; the body breaks consumed protein into amino acids in the stomach and intestines. There are three branched chain amino acids (BCAAs): leucine, isoleucine, and valine. Each has numerous benefits on various biological processes in the body. Unlike other amino acids, BCAAs are metabolised in the muscle. BCAAs have an anabolic/anti-catabolic effect on the muscle.
Meal Replacement Products
Meal Replacements Products (MRPs) are either pre-packaged powdered drink mixes or edible bars. Both are consumed in the place of a whole-food meal. Generally MRPs are high in protein, low in fat, have a low to moderate amount of carbohydrates, and contain a wide array of vitamins and minerals.
The majority of MRPs use whey protein, calcium caseinate or micellar casein, soy protein, and egg albumin as the protein source. Carbohydrates are typically derived from maltodextrin, oat fiber, brown rice, or wheat flour. Some also contain flax oil powder as a source of essential fatty acids.
MRPs can also contain other ingredients that are deemed beneficial to bodybuilders. These can include, but are not limited to: creatine monohydrate, glutamine peptides, l-glutamine, calcium alpha-ketoglutarate, additional amino acids, lactoferrin, conjugated linoleic acid, and medium chain triglycerides.
Prohormones are precursors to hormones and were most typically sold to bodybuilders as a precursor to the natural hormone testosterone. This conversion requires naturally occurring enzymes in the body. Side effects are not uncommon, as prohormones can also convert further into DHT and estrogen. To deal with this, many supplements also have aromatase inhibitors and DHT blockers such as chrysin and the more potent 6-OXO. To date most prohormone products have not been thoroughly studied, and the health effects of prolonged use are unknown. Although initially available over the counter, in 2004 their purchase was made illegal without a prescription in the US, as it remains so in almost all countries and is prescribed by most sporting bodies.
Creatine is an organic acid naturally occurring in the body that supplies energy to muscle cells for short bursts of energy (such as lifting weights) via creatine phosphate replenishment of ATP. A number of scientific studies have proven that creatine can increase strength, energy, and muscle mass in addition to reducing recovery time. Also, recent studies have shown that creatine improves brain function, improves recognition memory, and reduces mental fatigue. It increases what is known as cell volumization by drawing water into muscle cells, making them larger. This intracellular retention should not be confused with the common myth that creatine causes bloating (or intercellular water retention). Creatine is sold in a variety of forms, including Creatine monohydrate, Creatine ethyl ester and Creatine malate, among others. Though all types of creatine are sold for the same purposes, there are subtle differences between them, such as price, and necessary dosage. Non-supplemental suppliers of creatine include various types of offal, red meat, and kidney meat.
Claims that creatine could be stressful to the kidneys (due to primary renal elimination via creatinine) have not been proven in a scientific study, although no independent, large-scale survey has been conducted.  However in most studies that have been carried out about creatine they have found an increased amount of muscle cramping due to the water retention changes.
A thermogenic is a broad term for any supplement that the manufacturer claims will cause thermogenesis, resulting in an increased metabolic rate, increased body temperature and consequently an increased rate in the burning of body fat. Until recently almost every product found in this supplement category comprised the "ECA stack": ephedra, caffeine and aspirin. However, on February 6 2004 the Food and Drug Administration (FDA) banned the sale of ephedra and its alkaloid, ephedrine, for use in weight loss formulas. Several manufacturers replaced the ephedra component of the "ECA" stack with bitter orange or citrus aurantium (containing synephrine) instead of the ephedrine. To date the effectiveness of this new combination is not conclusive.
There are several naturally-occurring plants and vitamins as well as synthetic chemicals that supplement companies claim may produce an increase in testosterone levels. However, the validity of many of these products is questionable due to a lack of valid scientific research showing their effectiveness at this time. Some commonly taken supplements of this type are ZMA and Tribulus terrestris.
Excess testosterone can cause undesirable side effects, such as hair loss and acne, and may be converted into estrogens , which can have undesirable effects on males. Other supplements, such as aromatase inhibitors or antiaromatics, or Milk Thistle , may counteract some of these undesirable side-effects. 
- ↑ PDR Health"Soy Isoflavones" Retrieved on 2007-04-26.
- ↑ Becque, M. et al. (1999). Effects of oral creatine supplementation on muscular strength and body composition. Medicine & Science in Sports & Exercise, 32:3, 654-658.
- ↑ Birch, R. et al. (1994). The influence of dietary creatine supplementation on performance during repeated bouts of maximal isokinetic cycling in man. European Journal of Applied Physiology, 69, 268-270.
- ↑ Rae, C. et al. (2003). Oral creatine monohydrate supplementation improves brain performance: A double blind, placebo-controlled, cross-over trial. Proceedings of the Royal Society of London: Biological Sciences, 270:1529, 2147-2150.
- ↑ Ferrier, C. H. et al. (2001). NAA and creatine levels measured by H MRS relate to recognition memory. Neurology, 55, 1874-1883.
- ↑ Watanabe, A. et al. (2002). Effects of creatine on mental fatigue and cerebral hemoglobin oxygenation. Neuroscience Research, 42, 279-285.
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