Most supplements that have been marketed to improve health and/or exercise performance are based on theoretical applications derived from basic and/or clinical research studies. Based on these preliminary studies, a training device or supplement is often marketed to people proclaiming the benefits observed in these basic research studies. Although the theory may sound good, critical analysis of the theory often reveals flaws in scientific logic and/or that the claims made don't quite match up with the literature cited. If you do your homework, you can discern whether a supplement has been based on sound scientific evidence or not. To do so, we suggest you read reviews about the training method, nutrient, and/or supplement from researchers who have been intimately involved in this line of research and/or consult reliable references about nutritional and herbal supplements 48. We also suggest doing a search on the nutrient/supplement on the National Library of Medicine's Pub Med Online 9. A quick look at these references will often help you know whether the theory is plausible or not. In our experience, proponents of ergogenic aids often overstate claims made about training devices and/or nutritional supplements while opponents of nutritional supplements and ergogenic aids are either unaware and/or ignorant of research supporting their use. The sport nutrition specialist has the responsibility to know the literature and/or search available data bases to know whether there is merit or not to a proposed ergogenic aid.

The next question suggest asking is whether there is any well-controlled data showing the proposed ergogenic aid works as claimed in athletes or people involved in training. The first place we look is the list of references cited in marketing material supporting their claims. We look to see if the abstracts or articles cited are general references or specific studies that have evaluated the efficacy of the nutrient/supplement. We then critically evaluate the abstracts and articles by asking a series of questions.

▪ Are the studies simply basic research done in animals/clinical populations or have the studies been conducted on athletes? Studies reporting improved performance in rats may be insightful but research conducted on athletes is much more convincing.

▪ Were the studies well controlled? For ergogenic aid research, the study should be a placebo controlled, double blind, and randomized clinical trail if possible. This means that neither the researcher's nor the subject's were aware which group received the supplement or the placebo during the study and that the subjects were randomly assigned into the placebo or supplement group. At times, supplement claims have been based on poorly designed studies (i.e., small groups of subjects, no control group, use of unreliable tests, etc) and/or testimonials which may make interpretation much more difficult. Studies that are well controlled clinical trials provide stronger evidence as to the potential ergogenic value than those that are not well controlled.

▪ Do the studies report statistically significant results or are claims being made on non-significant means or trends reported? Appropriate statistical analysis of research results allows for an unbiased interpretation of data. Although studies reporting statistical trends may be of interest and lead researchers to conduct additional research, studies reporting statistically significant results are obviously more convincing. With this said, sport nutrition specialist must be careful not to commit type II statistical error (i.e., indicating that no differences were observed when a true effect was seen but not detected statistically). Since many studies on ergogenic aids (particularly in high level athletes) evaluate small numbers of subjects, results may not reach statistical significance even though large mean changes were observed. In these cases, additional research is warranted to further examine the potential ergogenic aid before conclusions can be made.

▪ Do the results of the studies cited match the claims made about the supplement? It is not unusual for marketing claims to greatly exaggerate the results found in the actual studies. Therefore, you should compare results observed in the studies to marketing claims. Reputable companies accurately report results of studies so that consumers can make informed decisions about whether to try a product or not.

▪ Were results of the study presented at a reputable scientific meeting and/or published in a peer-reviewed scientific journal? At times, claims are based on research that has either never been published or only published in an obscure journal. The best research is typically presented at respected scientific meetings and/or published in reputable peer-reviewed journals.

▪ Have the research findings been replicated at several different labs? The best way to know an ergogenic aid works is to see that results have been replicated in several studies preferably by a number of researchers. The most reliable ergogenic aids are those in which a number of studies, conducted at different labs, have reported similar results.

The final question we ask is whether the supplement is legal and/or safe. Some athletic associations have banned the use of various nutritional supplements (e.g., prohormones, ephedra, etc). Obviously, if the supplement is banned, the sport nutrition specialist should discourage its use. In addition, many supplements have not been studied for long-term safety. People who consider taking nutritional supplements should be well aware of the potential side effects so that they can make an informed decision regarding whether to use a supplement or not. Additionally, they should consult with a knowledgeable physician to see if there are any underlying medical problems that may contraindicate use. When evaluating the safety of a supplement, we suggest looking to see if any side effects have been reported in the scientific or medical literature. In particular, we suggest determining how long a particular supplement has been studied, the dosages evaluated, and whether any side effects were observed. We also recommend consulting the PDR for nutritional supplements and herbal supplements to see if any side effects have been reported and/or there are any known drug interactions. If no side effects have been reported in the scientific/medical literature, we generally will view the supplement as safe for the length of time and dosages evaluated.

The first component to optimize training and performance through nutrition is to ensure the athlete is consuming enough calories to offset energy expenditure 1101112. People who participate in a general fitness program (e.g., exercising 30 – 40 minutes per day, 3 times per week) can generally meet nutritional needs following a normal diet (e.g., 1,800 – 2,400 kcals/day or about 25 – 35 kcals/kg/day for a 50 – 80 kg individual) because their caloric demands from exercise are not too great (e.g., 200 – 400 kcals/session) 1. However, athletes involved in moderate levels of intense training (e.g., 2–3 hours per day of intense exercise performed 5–6 times per week) or high volume intense training (e.g., 3–6 hours per day of intense training in 1–2 workouts for 5–6 days per week) may expend 600 – 1,200 kcals or more per hour during exercise 113. For this reason, their caloric needs may approach 50 – 80 kcals/kg/day (2,500 – 8,000 kcals/day for a 50 – 100 kg athlete). For elite athletes, energy expenditure during heavy training or competition may be enormous. For example, energy expenditure for cyclists to compete in the Tour de France has been estimated as high as 12,000 kcals/day (150 – 200 kcals/kg/d for a 60 – 80 kg athlete) 1315. Additionally, caloric needs for large athletes (i.e., 100 – 150 kg) may range between 6,000 – 12,000 kcals/day depending on the volume and intensity of different training phases 13.

Although some argue that athletes can meet caloric needs simply by consuming a well-balanced diet, it is often very difficult for larger athletes and/or athletes engaged in high volume/intense training to be able to eat enough food in order to meet caloric needs 111131415. Maintaining an energy deficient diet during training often leads to significant weight loss (including muscle mass), illness, onset of physical and psychological symptoms of overtraining, and reductions in performance 12. Nutritional analyses of athletes' diets have revealed that many are susceptible to maintaining negative energy intakes during training. Susceptible populations include runners, cyclists, swimmers, triathletes, gymnasts, skaters, dancers, wrestlers, boxers, and athletes attempting to lose weight too quickly 11. Additionally, female athletes have been reported to have a high incidence of eating disorders 11. Consequently, it is important for the sport nutrition specialist working with athletes to ensure that athletes are well-fed and consume enough calories to offset the increased energy demands of training and maintain body weight. Although this sounds relatively simple, intense training often suppresses appetite and/or alters hunger patterns so that many athletes do not feel like eating 11. Some athletes do not like to exercise within several hours after eating because of sensations of fullness and/or a predisposition to cause gastrointestinal distress. Further, travel and training schedules may limit food availability and/or the types of food athletes are accustomed to eating. This means that care should be taken to plan meal times in concert with training as well as make sure athletes have sufficient availability of nutrient dense foods throughout the day for snacking between meals (e.g., drinks, fruit, carbohydrate/protein bars, etc) 11011. For this reason, sport nutritionists' often recommend that athletes consume 4–6 meals per day and snack in between meals in order to meet energy needs. Use of nutrient dense energy bars and high calorie carbohydrate/protein supplements provides a convenient way for athletes to supplement their diet in order to maintain energy intake during training.

The second component to optimizing training and performance through nutrition is to ensure that athletes consume the proper amounts of carbohydrate, protein and fat in their diet. Individuals engaged in a general fitness program can typically meet macronutrient needs by consuming a normal diet (i.e., 45–55% carbohydrate [3–5 grams/kg/day], 10–15% protein [0.8–1.0 gram/kg/day], and 25–35% fat [0.5–1.5 grams/kg/day]). However, athletes involved in moderate and high volume training need greater amounts of carbohydrate and protein in their diet to meet macronutrient needs. For example, in terms of carbohydrate needs, athletes involved in moderate amounts of intense training (e.g., 2–3 hours per day of intense exercise performed 5–6 times per week) typically need to consume a diet consisting of 55–65% carbohydrate (i.e., 5–8 grams/kg/day or 250 – 1,200 grams/day for 50 – 150 kg athletes) in order to maintain liver and muscle glycogen stores 110. Research has also shown that athletes involved in high volume intense training (e.g., 3–6 hours per day of intense training in 1–2 workouts for 5–6 days per week) may need to consume 8–10 grams/day of carbohydrate (i.e., 400 – 1,500 grams/day for 50 – 150 kg athletes) in order to maintain muscle glycogen levels 110. This would be equivalent to consuming 0.5 – 2.0 kg of spaghetti. Preferably, the majority of dietary carbohydrate should come from complex carbohydrates with a low to moderate glycemic index (e.g., grains, starches, fruit, maltodextrins, etc). However, since it is physically difficult to consume that much carbohydrate per day when an athlete is involved in intense training, many nutritionists and sport nutrition specialist recommend that athletes consume concentrated carbohydrate juices/drinks and/or consume high carbohydrate supplements to meet carbohydrate needs. While consuming this amount of carbohydrate is not necessary for the fitness minded individual who only trains 3–4 times per week for 30–60 minutes, it is essential for competitive athletes engaged in intense moderate to high volume training.

There has been considerable debate regarding protein needs of athletes 1617181920. Initially, it was recommended that athletes do not need to ingest more than the RDA for protein (i.e., 0.8 to 1.0 g/kg/d for children, adolescents and adults). However, research over the last decade has indicated that athletes engaged in intense training need to ingest about 1.5 – 2 times the RDA of protein in their diet (1.5 to 2.0 g/kg/d) in order to maintain protein balance 1617181920. If an insufficient amount of protein is obtained from the diet, an athlete will maintain a negative nitrogen balance which can increase protein catabolism and slow recovery. Over time, this may lead to lean muscle wasting and training intolerance 112.

For people involved in a general fitness program, protein needs can generally be met by ingesting 0.8 – 1.0 grams/kg/day of protein. It is generally recommended that athletes involved in moderate amounts of intense training consume 1 – 1.5 grams/kg/day of protein (50 – 225 grams/day for a 50 – 150 kg athlete) while athletes involved in high volume intense training consume 1.5 – 2.0 grams/kg/day of protein (75 – 300 grams/day for a 50 – 150 kg athlete) 21. This protein need would be equivalent to ingesting 3 – 11 servings of chicken or fish per day for a 50 – 150 kg athlete 21. Although smaller athletes typically can ingest this amount of protein in their normal diet, larger athletes often have difficulty consuming this much dietary protein. Additionally, a number of athletic populations have been reported to be susceptible to protein malnutrition (e.g., runners, cyclists, swimmers, triathletes, gymnasts, dancers, skaters, wrestlers, boxers, etc). Therefore, care should be taken to ensure that athletes consume a sufficient amount of quality protein in their diet in order to maintain nitrogen balance (e.g., 1.5 – 2 grams/kg/day).

However, it should be noted that not all protein is the same. Proteins differ based on the source that the protein was obtained, the amino acid profile of the protein, and the methods of processing or isolating the protein 22. These differences influence availability of amino acids and peptides that have been reported to possess biological activity (e.g., α-lactalbumin, β-lactoglobulin, glycomacropeptides, immunoglobulins, lactoperoxidases, lactoferrin, etc). Additionally, the rate and metabolic activity of the protein 22. For example, different types of proteins (e.g., casein and whey) are digested at different rates which directly affect catabolism and anabolism 22232425. Therefore, care should be taken not only to make sure the athlete consumes enough protein in their diet but also that the protein is high quality. The best dietary sources of low fat and high quality protein are light skinless chicken, fish, egg white and skim milk (casein and whey) 22. The best sources of high quality protein found in nutritional supplements is whey, colostrum, casein, milk proteins and egg protein 2122. Although some athletes may not need to supplement their diet with protein and some sport nutrition specialists may not think that protein supplements are necessary, suggestions that it is unethical for an sport nutrition specialist to recommend that some athletes supplement their diet with protein in order to meet dietary protein needs and/or provide essential amino acids following exercise in order to optimize protein synthesis is clearly not supported by the literature.

The dietary recommendations of fat intake for athletes are similar to or slightly greater than those recommended for non-athletes in order to promote health. Maintenance of energy balance, replenishment of intramuscular triacylglycerol stores and adequate consumption of essential fatty acids are of greater importance among athletes and allow for somewhat increased intake 26. This depends on the athlete's training state and goals. For example, higher-fat diets appear to maintain circulating testosterone concentrations better than low-fat diets 272829. This has relevance to the documented testosterone suppression which can occur during volume-type overtraining 30. Generally, it is recommended that athletes consume a moderate amount of fat (approximately 30% of their daily caloric intake), while increases up to 50% of kcal can be safely ingested by athletes during regular high-volume training 26. For athletes attempting to decrease body fat, however, it has been recommended that they consume 0.5 to 1 g/kg/d of fat 1. The reason for this is that some weight loss studies indicate that people who are most successful in losing weight and maintaining the weight loss are those who ingest less than 40 g/d of fat in their diet 3132 although this is not always the case 33. Certainly, the type of dietary fat (e.g. n-6 versus n-3; saturation state) is a factor in such research and could play an important role in any discrepancies 3435. Strategies to help athletes manage dietary fat intake include teaching them which foods contain various types of fat so that they can make better food choices and how to how to count fat grams 111.

In addition to the general nutritional guidelines described above, research has also demonstrated that timing and composition of meals consumed may play a role in optimizing performance, training adaptations, and preventing overtraining 1103637. In this regard, it takes about 4 hours for carbohydrate to be digested and begin to be stored as muscle and liver glycogen. Consequently, pre-exercise meals should be consumed about 4 to 6 h before exercise 10. This means that if an athlete trains in the afternoon, breakfast is the most important meal to top off muscle and liver glycogen levels. Research has also indicated that ingesting a light carbohydrate and protein snack 30 to 60 min prior to exercise (e.g., 50 g of carbohydrate and 5 to 10 g of protein) serves to increase carbohydrate availability toward the end of an intense exercise bout 3839. This also serves to increase availability of amino acids and decrease exercise-induced catabolism of protein 363839.

When exercise lasts more than one hour, athletes should ingest glucose/electrolyte solution (GES) drinks in order to maintain blood glucose levels, help prevent dehydration, and reduce the immunosuppressive effects of intense exercise 10404142434445. Following intense exercise, athletes should consume carbohydrate and protein (e.g., 1 g/kg of carbohydrate and 0.5 g/kg of protein) within 30 min after exercise as well as consume a high carbohydrate meal within two hours following exercise 13637. This nutritional strategy has been found to accelerate glycogen resynthesis as well as promote a more anabolic hormonal profile that may hasten recovery 464748. Finally, for 2 to 3 days prior to competition, athletes should taper training by 30 to 50% and consume 200 to 300 g/d of extra carbohydrate in their diet. This carbohydrate loading technique has been shown to supersaturate carbohydrate stores prior to competition and improve endurance exercise capacity 11037. Thus, the type of meal and timing of eating are important factors in maintaining carbohydrate availability during training and potentially decreasing the incidence of overtraining.

Vitamins are essential organic compounds which serve to regulate metabolic processes, energy synthesis, neurological processes, and prevent destruction of cells. There are two primary classifications of vitamins: fat and water soluble. The fat soluble vitamins include vitamins A, D, E, & K. The body stores fat soluble vitamins and therefore excessive intake may result in toxicity. Water soluble vitamins are B vitamins and vitamin C. Since these vitamins are water soluble, excessive intake of these vitamins are eliminated in urine. Table 1 describes RDA, proposed ergogenic benefit, and summary of research findings for fat and water soluble vitamins. Although research has demonstrated that specific vitamins may posses some health benefit (e.g., vitamin E, niacin, folic acid, vitamin C, etc), few have been reported to directly provide ergogenic value for athletes. However, some vitamins may help athletes tolerate training to a better degree by reducing oxidative damage (vitamin E, C) and/or help to maintain a healthy immune system during heavy training (vitamin C). Theoretically, this may help athletes tolerate heavy training leading to improved performance. The remaining vitamins reviewed appear to have little ergogenic value for athletes who consume a normal, nutrient dense diet. Since dietary analyses of athletes have found deficiencies in caloric and vitamin intake, many sport nutritionists' recommend that athletes consume a low-dose one a day multivitamin and/or a vitamin enriched post-workout carbohydrate/protein supplement during periods of heavy training. The American Medical Association also recently evaluated the available medical literature and recommended that Americans consume a one-a-day low-dose multivitamin in order to promote general health. Suggestions that there is no benefit of vitamin supplementation for athletes and/or it is unethical for an sport nutrition specialist to recommend that their clients take a one-a-day multi-vitamin and/or suggest taking other vitamins that may reduce cholesterol levels (niacin), serve as antioxidants (Vitamin E), decrease risk to heart disease (niacin, Vitamin E), or may help maintain a health immune system (Vitamin C) is not consistent with current available literature.

Minerals are essential inorganic elements necessary for a host of metabolic processes. Minerals serve as structure for tissue, important components of enzymes and hormones, and regulators of metabolic and neural control. Some minerals have been found to be deficient in athletes or become deficient in response to training and/or prolonged exercise. When mineral status is inadequate, exercise capacity may be reduced. Dietary supplementation of minerals in deficient athletes has generally been found to improve exercise capacity. Additionally, supplementation of specific minerals in non-deficient athletes has also been reported to affect exercise capacity. Table 2 describes minerals that have been purported to affect exercise capacity in athletes. Of the minerals reviewed, several appear to possess health and/or ergogenic value for athletes under certain conditions. For example, calcium supplementation in athletes susceptible to premature osteoporosis may help maintain bone mass. There is also recent evidence that dietary calcium may help manage body composition. Iron supplementation in athletes prone to iron deficiencies and/or anemia has been reported to improve exercise capacity. Sodium phosphate loading has been reported to increase maximal oxygen uptake, anaerobic threshold, and improve endurance exercise capacity by 8 to 10%. Increasing dietary availability of salt (sodium chloride) during the initial days of exercise training in the heat has been reported to help maintain fluid balance and prevent dehydration. Finally, zinc supplementation during training has been reported to decrease exercise-induced changes in immune function. Consequently, somewhat in contrast to vitamins, there appear to be several minerals that may enhance exercise capacity and/or training adaptations for athletes under certain conditions. However, although ergogenic value has been purported for remaining minerals, there is little evidence that boron, chromium, magnesium, or vanadium affect exercise capacity or training adaptations in healthy individuals eating a normal diet. Suggestions that there is no benefit of mineral supplementation for athletes and/or it is unethical for an sport nutrition specialist to recommend that their clients take minerals that research has shown may affect health and/or performance is not consistent with current available literature.

The most important nutritional ergogenic aid for athletes is water. Exercise performance can be significantly impaired when 2% or more of body weight is lost through sweat. For example, when a 70-kg athlete loses more than 1.4 kg of body weight during exercise (2%), performance capacity is often significantly decreased. Further, weight loss of more than 4% of body weight during exercise may lead to heat illness, heat exhaustion, heat stroke, and possibly death 45. For this reason, it is critical that athletes consume a sufficient amount of water and/or GES sports drinks during exercise in order to maintain hydration status. The normal sweat rate of athletes ranges from 0.5 to 2.0 L/h depending on temperature, humidity, exercise intensity, and their sweat response to exercise 45. This means that in order to maintain fluid balance and prevent dehydration, athletes need to ingest 0.5 to 2 L/h of fluid in order to offset weight loss. This requires frequent ingestion of 6–8 oz of cold water or a GES sports drink every 5 to 15-min during exercise 4549505152. Athletes and should not depend on thirst to prompt them to drink because people do not typically get thirsty until they have lost a significant amount of fluid through sweat. Additionally, athletes should weigh themselves prior to and following exercise training to ensure that they maintain proper hydration 4549505152. The athlete should consume 3 cups of water for every pound lost during exercise in order adequately rehydrate themselves 45. Athletes should train themselves to tolerate drinking greater amounts of water during training and make sure that they consume more fluid in hotter/humid environments. Preventing dehydration during exercise is one of the most effective ways to maintain exercise capacity. Finally, inappropriate and excessive weight loss techniques (e.g., cutting weight in saunas, wearing rubber suits, severe dieting, vomiting, using diuretics, etc) are extremely dangerous and should be prohibited. Sport nutrition specialists can play an important role in educating athletes and coaches about proper hydration methods and supervising fluid intake during training and competition.

Convenience supplements are meal replacement powders (MRP's), ready to drink supplements (RTD's), energy bars, and energy gels. They currently represent the largest segment of nutrition industry representing 50 – 75% of most company's sales. They are typically fortified with 33 – 50% of the RDA for vitamins and minerals and typically differ on the amount of carbohydrate, protein, and fat they contain. They may also differ based whether they are fortified with various nutrients purported to promote weight gain, enhance weight loss, and/or improve performance. Most people view these supplements as a high quality snacks and/or use them to help control caloric intake when trying to gain and/or lose weight. In our view, MRP's, RTD's, and energy bars/gels can provide a convenient way for people to meet specific dietary needs and/or serve as good alternatives to fast food. Use of these types of products can be particularly helpful in providing carbohydrate, protein, and other nutrients prior to and/or following exercise in an attempt to optimize nutrient intake when an athlete doesn't have time to sit down for a good meal. However, they should be used to improve dietary availability of macronutrients – not as a replacement for a good diet. Care should also be taken to make sure they do not contain any banned or prohibited nutrients.

The following provides an analysis of the literature regarding purported weight gain supplements and our general interpretation of how they should be categorized based on this information. Table 3 summarizes how we currently classify the ergogenic value of a number of purported performance-enhancing, muscle building, and fat loss supplements based on an analysis of the available scientific evidence.