This article reviews the evidence-based ergogenic potential and adverse effects of 14 of the most common products in use by recreational and elite athletes today. Both legal and prohibited products are discussed. This is an aggressively marketed and controversial area of sports medicine worldwide. It is therefore prudent for the clinician to be well versed in the more popular supplements and drugs reputed to be ergogenic in order to distinguish fact from fiction.
Antioxidants, proteins and amino acids are essential components of diet, but additional oral supplementation does not increase endurance or strength. Caffeine is ergogenic in certain aerobic activities. Creatine is ergogenic in repetitive anaerobic cycling sprints but not running or swimming. Ephedrine and pseudoephedrine may be ergogenic but have detrimental cardiovascular effects. Erythropoietin is ergogenic but increases the risk of thromboembolic events. β-Hydroxy-β-methylbutyrate has ergogenic potential in untrained individuals, but studies are needed on trained individuals. Human growth hormone and insulin growth factor-I decrease body fat and may increase lean muscle mass when given subcutaneously. Pyruvate is not ergogenic. The androgenic precursors androstenedione and dehydroepiandrosterone have not been shown to increase any parameters of strength and have potentially significant adverse effects. Anabolic steroids increase protein synthesis and muscle mass but with many adverse effects, some irreversible. Supplement claims on labels of product content and efficacy can be inaccurate and misleading.
Products that claim to be performance enhancing are popular with recreational and elite athletes. Some are classified as drugs, others as supplements. Drugs that are used for medical purposes but have ergogenic properties are prohibited by most major sport governing bodies, since it is the elite athlete that is most likely to be tempted by such products. Supplements, however, are marketed aggressively to all types of athletes, which has generated its own controversy in this very profitable industry.[1]
Often, performance-enhancing products are purchased based on popular magazine advertisements, peer or coach recommendation rather than professional medical advice.[2,3]Furthermore, some products are popular and marketed as ergogenic despite a lack of objective evidence to support claims of an ergogenic effect. In the US for example, ergogenic claims of supplements can be made without verification by the Food and Drug Administration (FDA), ever since the controversial passage of the Dietary Supplement Health and Education Act in 1994.[4]
For this review, the Medline database was utilised to research the products listed (table I). Few studies had sample sizes of greater than 20 per group. Therefore, whenever possible, crossover designs were given high priority. Reviews of particular supplements or drugs were also analysed. Only reviews that provided a critique of studies rather than a rehashing of Medline abstracts were utilised. Many studies on over-the-counter (OTC) supplements were funded by supplement companies. While this did not necessarily exclude the study from consideration, conclusions from such studies were carefully assessed since supplements do not undergo the rigorous multiple-phase scrutiny of FDA approval. Surveys and case reports were judiciously utilised as some products have a paucity of controlled studies.
Table I. Popular spo...Image Tools
Table I. (continued)...Image Tools