Nutrition and Athletic Performance

Nancy R. Rodriguez, PhD, RD, CSSD, FACSM; Nancy M. DiMarco, PhD, RD, CSSD, FACSM; Susie Langley, MS, RD, CSSD

Disclosures

March 01, 2010

In This Article

Dietary Supplements and Ergogenic Aids

The overwhelming number and increased availability of sports supplements presents an ongoing challenge for the practitioner and the athlete to keep up-to-date about the validity of the claims and scientific evidence. Although dietary supplements and nutritional ergogenic aids, such as nutritional products that enhance performance, are highly prevalent, the fact remains that very few improve performance[117,118,119] and some may cause concern.

In the United States, the Dietary Supplements and Health Education Act of 1994 allows supplement manufacturers to make health claims regarding the effect of products on body structure or function but not therapeutic claims to "diagnose, mitigate, treat, cure, or prevent" a specific disease or medical condition.[117,120] As long as a special supplement label indicates the active ingredients and the entire ingredients list is provided, claims for enhanced performance can be made, valid or not. The Act, however, made the FDA responsible for evaluating and enforcing safety. In 2003, the US/FDA Task Force on Consumer Health Information for Better Nutrition proposed a new system for evaluating health claims that uses an evidence-based model and is intended to help consumers determine effectiveness of ergogenic aids and dietary supplements more reliably.[117] Although all manufacturers are required by the FDA to analyze the identity, purity, and strength of all of their products' ingredients, they are not required to demonstrate the safety and efficacy of their products.

Canada regulates supplements as medicine or as natural health products (NHP). Products regulated in Canada as NHP must comply with Natural Health Products Regulations (2003) and manufacturers are allowed to make a full range of claims (structure/function, risk reduction, treatment, prevention) as supported by scientific evidence.[117] In Canada, sports supplements such as sport drinks, protein powders, energy bars, and meal replacement products/beverages are regulated by Health Canada's Canadian Food Inspection Agency, whereas energy drinks, vitamin/mineral and herbal supplements, vitamin-enhanced water, and amino acid supplements fall under the NHP Regulations. Anabolic steroids are considered drugs and are tightly regulated under the Controlled Drugs & Substances Act.

Sports dietitians should consider the following factors in evaluating nutrition-related ergogenic aids: validity of the claims relative to the science of nutrition and exercise, quality of the supportive evidence provided (double-blinded, placebo-controlled scientific studies vs testimonials), and health and legal consequences of the claim.[121,122] The safety of ergogenic aids remains in question. Possible contamination of dietary supplements and ergogenic aids with banned or nonpermissable substances remains an issue of concern. Therefore, sports dietitians and athletes must proceed with caution when considering the use of these types of products. Ultimately, athletes are responsible for the product they ingest and any subsequent consequences. Dietary supplements or ergogenic aids will never substitute for genetic makeup, years of training, and optimum nutrition.

Both national [National Collegiate Athletic Association (NCAA; www.ncaa.org), United States Anti-Doping Agency (www.usantidoping.org)] and international sports organizations [World Anti-Doping Agency (WADA; (www.wada-ama.org)] limit the use of certain ergogenic aids and require random urine testing of athletes to ensure that certain products are not consumed. In Canada, the Canadian Centre for Ethics in Sport (www.cces.ca) is the organization which checks for banned substances.

The ethical use of performance-enhancing substances is a personal choice and remains controversial.[117] Therefore, it is important that the qualified sports nutrition professional keep an open mind when working with elite athletes to effectively assess, recommend, educate, and monitor athletes who contemplate using or actively take dietary supplements and/or ergogenic aids.[117] Credible and responsible information regarding the use of these products should be made available by qualified health professionals such as Board Certified Specialists in Sports Dietetics (CSSD) who carefully evaluate the risk-benefit ratio, including a complete dietary assessment.

It is beyond the scope of this article to address the multitude of ergogenic aids used by athletes in North America. From a practical perspective, however, most ergogenic aids can be classified into one of four categories: 1. those that perform as claimed; 2. those that may perform as claimed but for which there is insufficient evidence of efficacy at this time; 3. those that do not perform as claimed; and 4. those that are dangerous, banned, or illegal and, therefore, should not be used.[122]

1. Ergogenic aids that perform as claimed

Creatine. Creatine is currently the most widely used ergogenic aid among athletes wanting to build muscle and enhance recovery.[118,123,124,125] Creatine has been shown to be effective in repeated short bursts of high-intensity activity in sports that derive energy primarily from the ATP-CP energy system such as sprinting and weight lifting but not for endurance sports such as distance running.[32,117,126,127,128] Most of the researches on creatine have been conducted in a laboratory setting with male athletes.

The most common adverse effects of creatine supplementation are weight (fluid) gain, cramping, nausea, and diarrhea.[32,117,129] Although widely debated, creatine is generally considered safe for healthy adults, despite anecdotal reports of dehydration, muscle strains/tears, and kidney damage.[130,131,132] Although the effects of long-term use of creatine remain unknown, studies to date do not show any adverse effects in healthy adults from creatine supplementation.[133] Nevertheless, health care professionals should carefully screen athletes using creatine for any risk of liver or kidney dysfunction or, in rare instances, anterior compartment syndrome.

Caffeine. The potential ergogenic effects of caffeine may be more closely related to its role as a CNS stimulant and the associated decreased perception of effort as opposed to its role in mobilizing of free fatty acids and sparing of muscle glycogen.[117,134] In 2004, WADA moved caffeine from the restricted list to its Monitoring Programme. However, caffeine is still a restricted substance by the NCAA, where a positive doping test would be a caffeine level >15 μg·mL−1 of urine. New evidence shows that caffeine, when used in moderation, does not cause dehydration or electrolyte imbalance.[135,136,137,138] However, when rapid hydration is necessary, athletes should rely on noncaffeinated and nonalcoholic beverages.

The use of high-energy drinks containing caffeine can be ergolytic and potentially dangerous when used in excess or in combination with stimulants or alcohol or other unregulated herbals and should be discouraged.[32,117,139,140,141] Adverse effects of caffeine are anxiety, jitteriness, rapid heartbeat, gastrointestinal distress, and insomnia, and it could be ergolytic for novice users.[134,142] There is little evidence to promote use of caffeine alone as a weight-loss aid.[118]

Sports Drinks, Gels, and Bars. Sports drinks, gels, and bars are commonly used as convenient dietary supplements or ergogenic aids for busy athletes and active people. It is important that qualified nutrition professionals educate consumers about label reading, product composition, and appropriate use of these products (before, during, and after training and competition).

Sodium Bicarbonate. Sodium bicarbonate may be an effective ergogenic aid as a blood buffer (role in acid-base balance and prevention of fatigue), but its use is not without unpleasant adverse effects such as diarrhea.[117,143]

Protein and Amino Acid Supplements. Current evidence indicates that protein and amino acid supplements are no more or no less effective than food when energy is adequate for gaining lean body mass.[30,31,117] Although widely used, protein powders and amino acid supplements are a potential source for illegal substances such as nandrolone, which may not be listed on the ingredient label.[144,145]

2. Ergogenic aids that may perform as claimed but for which there is insufficient evidence

The ergogenic aids that have claims as health and performance enhancers include glutamine, β-hydroxymethylbutyrate, colostrum, and ribose.[117] Preliminary studies concerning these ergogenic aids are inconclusive as performance enhancers. These substances are not banned from use by athletes (www.wada-ama.org/en/prohibitedlist.ch2).

3. Ergogenic aids that do not perform as claimed

The majority of ergogenic aids currently on the market are in this category.[122] These include amino acids, bee pollen, branched chain amino acids, carnitine, chromium picolinate, cordyceps, coenzyme Q10, conjugated linoleic acid, cytochrome C, dihydroxyacetone, γ-oryzanol, ginseng, inosine, medium-chain triglycerides, pyruvate, oxygenated water, and vanadium. This list is by no means exhaustive, and it is likely that other substances would be best placed in this category. Similarly, it is possible for any of these compounds to eventually move from this to another category after appropriate scientific inquiry and evaluation. To date, however, none of these products has been shown to enhance performance and many have had adverse effects.[122]

4. Ergogenic aids that are dangerous, banned, or illegal

The ergogenic aids in this category should not be used and are banned by WADA. Examples are androstenedione, dehydroepiandrosterone, 19-norandrostenedione, 19-norandrostenediol, and other anabolic, androgenic steroids, Tribulus terrestris, ephedra, strychnine, and human growth hormone. Because this is an evolving field, sports dietitians need to consistently consider the status of various nutritional ergogenic aids.

The Vegetarian Athlete

The Position Statement of the American Dietetic Association and Dietitians of Canada on vegetarian diets (2003) provides appropriate dietary guidance for vegetarian athletes. This article provides additional considerations for vegetarians who participate in exercise. Well-planned vegetarian diets seem to effectively support parameters that influence athletic performance, although studies on this population are limited.[31,146] Plant-based high-fiber diets may reduce energy availability. Monitoring body weight and body composition is the preferred means of determining whether energy needs are met. Some individuals, especially women, may switch to vegetarianism as a means of avoiding red meat and/or restricting energy intake to attain a lean body composition favored in some sports. Occasionally, this may be a red flag for disordered eating and increase the risk for the female athlete triad.[72,73] Because of this association, coaches, trainers, and other health professionals should be alert when an athlete becomes a vegetarian and should ensure that appropriate weight is maintained.

Although most vegetarian athletes meet or exceed recommendations for total protein intake, their diets often provide less protein than those of nonvegetarians.[31] Thus, some individuals may need more protein to meet training and competition needs.[31] Protein quality of plant-based diets should be sufficient provided a variety of foods that supply adequate energy is consumed.[31] Protein quality is a potential concern for individuals who avoid all animal proteins such as milk and meat (i.e., vegans). Their diets may be limited in lysine, threonine, tryptophan, or methionine.[39]

Because plant proteins are less well digested than animal proteins, an increase in intake of approximately 10% protein is advised.[15] Therefore, protein recommendations for vegetarian athletes approximate 1.3-1.8 g·kg−1·d−1.[52] Vegetarians with relatively low energy intakes should choose foods wisely to ensure protein intakes are consistent with these recommendations.

Vegetarian athletes may be at risk for low intakes of energy, fat, vitamins B12, riboflavin, and D, calcium, iron, and zinc, which are readily available from animal proteins. Iron is of particular concern because of the low bioavailability of nonheme plant sources. Iron stores of vegetarians are generally lower than omnivores.[52] Vegetarian athletes, especially women, may be at greater risk for developing iron deficiency or anemia. Routine monitoring of iron status is recommended for vegetarian athletes, especially during periods of rapid growth (i.e., adolescence and pregnancy). Very low fat diets or avoidance of all animal protein may lead to a deficiency of essential fatty acids. Sport dietitians should educate novice vegetarian athletes on resources for menu planning, cooking, and shopping—especially high-quality plant protein combinations and acceptable animal sources (i.e., dairy and eggs) as well as foods rich in or fortified with key nutrients (calcium, vitamins D, B12, and riboflavin, iron, and zinc).[52]

Roles and Responsibilities of the Sports Dietitian

As nutrition information advances in quantity and complexity, athletes and active individuals are presented with a myriad of choices and decisions about appropriate and effective nutrition for activity and performance. Increasingly, athletes and active individuals seek professionals to guide them in making optimal food and fluid choices. Although many athletes and active individuals view winning or placing in an event to be the ultimate evidence of the effectiveness of their dietary regimens, sports dietitians should address the combined goals of health and fitness, enhanced capacity to train, and optimal athletic performance. Therefore, sports dietitians should be competent in the following areas:

Roles

  • Conduct comprehensive nutrition assessment and consultation

  • Educate in food selection, purchasing, and preparation

  • Provide medical nutrition therapy in private practice, health care, and sports settings

  • Identify and treat nutritional issues that impact health and performance

  • Address energy balance and weight management issues

  • Address nutritional challenges to performance (gastrointestinal disturbances, iron depletion, eating disorders, female athlete triad, food allergies, and supplement use)

  • Track and document measurable outcomes of nutrition services

  • Promote wound and injury healing

  • Oversee menu planning and design, including pre- and postevent and travel

  • Develop and oversee nutrition polices and procedures

  • Evaluate the scientific literature and provide evidence-based assessment and application

Responsibilities

  • Apply sports nutrition science to fueling fitness and performance

  • Develop personalized nutrition and hydration strategies

  • Advise on dietary supplements, ergogenic aids, meal and fluid replacement products, sports drinks, bars, and gels

  • Evaluate dietary supplements and sports foods for legality, safety, and efficacy

  • Provide nutrition strategies to delay fatigue during exercise and speed recovery from training

  • Help enhance athletic training capacity and performance

  • Participate in identifying and treating disordered eating patterns

  • Provide nutrition strategies to reduce risk of illness/injury and facilitate recovery

  • Promote career longevity for collegiate and professional athlete and all active individuals

  • Recruit and retain clients and athletes in practice

  • Provide sports nutrition as member of multidisciplinary/medical/health care teams

  • Provide reimbursable services (diabetes medical nutrition therapy)

  • Design and conduct sports team education

  • Serve as a mentor for developing sports dietetics professionals

  • Maintain credential(s) by actively engaging in profession-specific continuing education activities

The aforementioned responsibilities should be routine expectations of sporting and sports medicine organizations that employ qualified sports dietitians and of clients and athletes seeking valid sports nutrition information and advice.

In 2005, the Commission on Dietetic Registration (CDR; the credentialing agency of the American Dietetic Association) created a specialty credential for food and nutrition professionals who specialize in sports dietetic practice. The Board Certification Specialist in Sports Dietetics (CSSD) credential is designed as the premier professional sports nutrition credential in the United States. Specialists in Sports Dietetics provide safe, effective, evidence-based nutrition assessment, guidance, and counseling for health and performance for athletes, sport organizations, and physically active individuals and groups. The credential requires current Registered Dietitian (RD) status, maintenance of RD status for a minimum of 2 yr, and documentation of 1500 sports specialty practice hours as an RD within the past 5 yr. For more information, readers are referred to www.cdrnet.org/whatsnew/Sports.htm.

ADA/DC/ACSM position adopted by the ADA House of Delegates Leadership Team on July 12, 2000 and reaffirmed on May 25, 2004; approved by Dietitians of Canada on July 12, 2000 and approved by the American College of Sports Medicine Board of Trustees on October 17, 2000. The Coaching Association of Canada endorses this position paper. This position is in effect until December 31, 2012. ADA/DC/ACSM authorizes republication of the position, in its entirety, provided full and proper credit is given. Readers may copy and distribute this article, providing such distribution is not used to indicate an endorsement of product or service. Commercial distribution is not permitted without the permission of ADA. Requests to use portions of the position must be directed to ADA headquarters at 800/877-1600, ext 4835, or ppapers@eatright.org.

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