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Sports Supplements: A Modern Case of Caveat Emptor

 

by P. Z. Pearce, MD

 

Current Sports Medicine Reports 2005, 4: 171-178Philadelphia, PA
Current Science Inc. ISSN 1537-890x

 

Performance is the combination of favorable genetics, proper training, and a sound approach to nutrition. Athletes attempting to gain a competitive edge often try artificial means of improving speed , strength and endurance. Although some use oral or injectable medications, others turn to nutritional supplements. This article focuses on some of the most common methods athletes use to enhance performance. Reported dosages, representative studies, and potential side effects are reviewed, along with guidelines for evaluating supplements, and the claims of their manufacturers.

 

Introduction

 

"I never really rejoiced over the victory in Hawaii," Nina Kraft said (after winning the 2004 Ironman Triathlon World Championship). "I was ashamed the entire time, especially in front of my family. I cheated." Barry Bonds, Marion Jones, or Jason Giambi could just have easily made that statement. Athletes seeking to better their opponents will do just about anything to gain a competitive edge, even if it could be harmful to their health.

 

Performance is the combination of favorable genetics, proper training, and a sound approach to nutrition. Nina admitted using r-EPO (recombinant erythropoietin) before the big event, to increase her erythrocyte mass, and therefore oxygen-carrying capacity. She had never heard of the 19 Belgian and Dutch cyclists who died of "heart attacks and strokes" from 1987 to 1990, immediately after r-EPO was introduced. The combined effects of dehydration at the end of a long endurance race, and an artificially elevated hematocrit, lead to a fatal hyperviscosity syndrome. What's worse is that Nina may not have even cared. Bob Goldman, MD, in a 1995 survey of Olympic and other elite athletes, found that 195 out of 198 would use a performance-enhancing substance, if it could not be detected and would guarantee they win every race. Even if it were later discovered that they would unfortunately die in 5 years, more than half surveyed said they would still take it [1].

 

The manufacture of nutritional supplements has grown into a $17 billion-per-year industry, with over 90 brands marketing some 300 products to consumers. Of these, 235 claim to increase muscle growth and strength. In a 1994 meta-analysis of 10,274 athletes across 15 different sports, 46 percent admitted to using some form of supplement. Elite athletes (professional and Olympic) were more likely than those in college or high school. During the 2000 Summer Olympic Games in Sydney, of the 2758 athletes tested, 78.6 percent d eclared taking some form of supplement within 3 days of competition [2*]. National Collegiate Athletic Association (NCAA) figures for 2001 indicate that 53 percent of collegiate athletes took supplements, the most common being creatine and protein powder [3]. The pattern is constantly changing, and seems to reflect market trends of a largely unregulated industry. In 1991 Congress passed the Nutrition Labeling and Education Act, which would have regulated supplements as drugs. Unfortunately, before that bill could be funded and enforced, the 1994 Dietary Supplement and Health Education Act reaffirmed that these are food substances, and manufacturers are not responsible for product purity, if there is no claim to treat a specific disease.

 

Studies to prove the efficacy of supplements are often poorly designed, with few subjects and no control group. Benefits are often demonstrated by stringing together plausible theories, but unfortunately drawing inaccurate conclusions. They extrapolate anecdotal information, and imply it is representative of the whole population, or generalize data from deficiency states. For example, replacement of inadequate iron or chromium stores can certainly improve performance, but supplementing normal subjects does not.

 

Nutrition

 

Performance begins with sound nutrition, and supplements are simply oral food products that augment an individual's normal diet. The basic diet plan includes two servings of dairy (milk/yogurt/cheese), two servings of meat (fish/poultry/beans), four servings of fruits and vegetables, and four servings of grain or cereal, totaling 1200 to 1500 kcal/d. That simple formula will usually provide the 40 fundamental nutrients, as listed in Table 1 [4**]. The composition of this diet should consist of roughly 60 percent to 70 percent carbohydrate, 20 percent protein, and 10 percent fat. Many of the athletes I deal with do not understand the importance of following the same basic guidelines, and simply increasing caloric intake to offset the requirements of exercise. The following five nutrients have the greatest impact on performance.

 

Water

 

Water is essential for cellular function, and athletes lose 2 to 4 L/h in sweat. Absorption from the gut (mainly small intestine) is dependent upon individual variability, carbohydrate and electrolyte concentration, and intensity of exercise. Maximal rates of 1 to 1.5 L/h are observed with sugar concentration of 5 percent to 7 percent, and at VO 2 max less than 75 percent. The two most common strategies for fluid replacement are programmed drinking, and judicious fluid replacement. The former involves loading with 8 mL/kg body weight (400 - 600 mL or 16 - 20 oz) 10 to 15 minutes before exercise, then consuming fluid on a schedule of 3 mL/kg body weight (150 - 250 mL or 6 - 8 oz) every 15 to 20 minutes [5]. I prefer to account for individual variance in sweat rate and gastric emptying by having an athlete weigh nude and dry, exercise for 1 hour, then weigh nude and dry again. Using the formula "a pint's a pound the world around," you can calculate fluid replacement more accurately. As we have seen at the Ironman Triathlon in Hawaii , replacing too much fluid can lead to nausea or vomiting, and the potentially life-threatening condition of hyponatremia (low serum sodium). Glycerol loading has been suggested as a means of retaining more water during endurance exercise, but several studies refute that claim (Craig A. Horswill, Ph.D., Gatorade Sports Science Institute, 2002).

 

Sodium

 

Sodium is the most common electrolyte in sweat, and is lost in significant amounts during exercise. The average American consumes 8 to 12 g of salt a day, with a recommended daily allowance (RDA) of 3.8 to 5.8 g. There are many theories regarding the etiology of exercise-induced cramping, but fatigue, dehydration, and loss of sodium are central to most [6**]. Athletes are usually low in sodium due to increased sweat loss, and should salt their food. I recommend monitoring blood pressure, but only 20 percent of the population develops hypertension in response to increased dietary sodium intake. Salt can also be taken as tablets, or included in a sports drink, where palatability is the limiting factor. An athlete with one gene for cystic fibrosis (roughly one in every 31 white Americans), will sweat more salt, and may require significant replacement to avoid cramping (E. Randy Eichner, MD; Personal communication, 2004).

 

Carbohydrates

 

There are two forms of carbohydrate, simple sugar and the complex form, known as starch (rice, potatoes, pasta). When maximizing caloric intake to offset the requirements of exercise, I recommend 50 percent to 60 percent be taken in the form of complex carbohydrate. The simple sugars include glucose, fructose, galactose, and maltodextrins (strings of glucose in a small chain of 8 to 12 units). They are usually included in fluid replacement and electrolyte drinks (FREDs), to provide energy during exercise. Because each sugar enhances fluid absorption from the gut by a different mechanism, it makes sense to include a combination of several different types [7]. A carbohydrate concentration of 5 percent to 7 percent maximizes both energy replacement, and absorption from the gut during activity. Fructose alone, at a concentration greater than 3 percent to 4 percent, slows absorption and leads to gastrointestinal (GI) distress (nausea, diarrhea). Because all FREDs provide water, carbohydrate, and electrolytes, selection becomes a matter of taste and GI tolerance. It is also helpful for the athlete to train with the same beverage that will be offered at their race or competition.

 

Carbohydrate loading, popular in the 1970s, is no longer a common practice. Several days of a high-protein diet (inadequate calories) and intense exercise were followed by high carbohydrate intake, inducing the liver and muscles to store more glycogen. It has been found that athletes consuming 70 percent of their calories as carbohydrate already have maximal glycogen stores. A high-carbohydrate diet the night before and morning of an event, however, does provide a good source of fuel in an easily digestible form.

 

Protein

 

Although essential for growth and repair, protein is a poor source of fuel. It does provide 4.1 kcal/g, but for every 100 kcal consumed, it takes 30 kcal for conversion to a useful fuel. This is known as the specific dynamic action of a food, and is highest for protein. That is why the popular high-protein diet provides inadequate calories, and is simply not appropriate for athletes. Weight loss, in this form of controlled starvation, usually occurs because it is very difficult to consume enough protein to sustain even an inactive individual. Protein metabolism also produces many by-products, which must be cleared by the kidneys. The breakdown of purine amino acids results in the formation of uric acid, which may accumulate in the blood and precipitate into joints, as the painful condition known as gout.

 

The RDA for protein of 0.8 g/kg body weight/d should be increased to 1.2 to 1.4 g/kg in endurance athletes [8*], and 1.4 to 1.8 g/kg in strength athletes [9*]. There is no evidence that further supplementation is anabolic. Recently it has been suggested that protein be added to FREDs. Although some studies have been promising [10] there is a general consensus that protein is a poor fuel and more appropriate to aid in recovery after activity (Robert Murray, PhD, Gatorade Sports Science Institute; Personal communication, 2004).

 

Fat

 

An excellent fuel, providing 9.3 kcal/g, fat is also a source of the essential fatty acids (linoleic, linolenic, and arachadonic), which cannot be synthesized in the body. Although fat is difficult to digest, and slows gastric emptying, it has recently been suggested that a high-fat diet could actually improve performance. This concept was popularized by Phil Maffetone, who worked with professional triathlete, Mark Allen [11]. He was accomplished at shorter races, but always seemed to run out of energy at the Ironman. Mark had an incredibly low body fat, which was a disadvantage in endurance events, where 9 0 percent of your calories come from stored fat after 90 minutes of activity (90-90 rule) [12**]. Similar to other deficiency states, when Mark changed his diet to include 40 percent of calories from fat, he was able to succeed at longer distances. Because of its association with atherosclerosis and heart disease, fat should only contribute 10 percent to 15 percent of daily caloric requirements.

 

Supplements

 

For every athlete taking some oral or injectable medication, there are thousands who use nutritional supplements. A survey of 263 division III college football players revealed that 87 percent (230) used some form of dietary supplement to increase performance. The 12 most commonly used, of the 24 substances reported, are presented in Table 2 (Robert Sallis, MD; Personal communication, 2004). These data are felt to be representative of similar surveys, and therefore reflect current trends. Supplements can affect performance in several ways, so I will present them as anabolic agents, metabolic stimulants, amino acids, and antioxidants.

 

Anabolic Agents

 

Although this article deals with oral supplements, I thought it would be instructive to begin this discussion with a brief history of anabolic steroids, considered the gold standard in performance enhancement. Many of the popular oral supplements attempt in some way to duplicate the effects of anabolic steroids, and testosterone.

 

Steroids

 

In 1935, two German researchers discovered that testosterone given to dogs could increase muscle mass [13]. It is widely believed (but unsubstantiated) that Hitler had mice testes implanted under the skin of the forearm in his SS troops, to increase their aggression [14]. Testosterone was used to create a positive nitrogen balance (and improved work capacity) in malnourished concentration camp prisoners. Russian and other European athletes then began experimenting with steroids in the 1940s and early 1950s. Their success was proven at the 1952 Olympic Games in Helsinki, where Soviet weight lifters took home almost all of the gold and silver medals. At the 1956 world Games in Moscow, American physician John Ziegler saw Soviet athletes using testosterone, and his later attempts at separating the androgenic from anabolic effects, lead to the development of dianabol [15]. The use of anabolic steroids spread, and it was not until the 1976 Summer Olympic Games in Montreal, that a sports governing body actually banned dianabol, and related synthetic drugs. On March 1, 1991, the Federal Anabolic Control Act was passed, which made natural and artificial steroids a schedule III controlled substance. Legislation, however, has had little impact on the use of anabolic steroids in sports. Although Major League Baseball currently has the spotlight, it's alarming that of the roughly 2 million US athletes believed to be using steroids; 20 percent are college, 4 percent to 11 percent high school, and 2 percent to 3 percent junior high students.

 

A related anabolic agent, human growth hormone (HGH) has recently become popular among athletes. HGH is a 191-amino acid, single-chain polypeptide, which exerts its anabolic effect by increasing production of mRNA, cellular uptake of amino acids, and thus protein synthesis. Although this is essential for normal growth and development, when administered to mature adults, the results are less promising. The hypertrophy of skeletal muscle induced with hormonal stimulation does not seem to be as functional as that produced by resistance exercise. This is supported by several studies in healthy subjects, which show increases in muscle bulk, but no real change in performance [16].

 

Androstenedione / dehydroepiandrostenedione

 

There are two nutritional supplements that attempt to mimic the anabolic effects of testosterone, by increasing hormone production. Table 3 shows the metabolic pathways for synthesis of testosterone from cholesterol. Early investigators looked to the precursors, dehydroepiandrostenedione (DHEA), and androstenedione (andro), as possible ergogenic supplements. DHEA was first isolated from the adrenal gland in 1937, and later found naturally in wild yams. With doses of 50 to 100 m/d, it has been shown to increase androgenic steroid plasma levels in men and women over 45, but there are few good studies in young athletes [17]. Weight lifters reportedly find much higher doses effective, but these claims are not substantiated in the literature. The side effects are similar to anabolic steroids, including acne, hair loss, striae, irritability, increased low-density lipoprotein and decreased high-density lipoprotein cholesterol, gynecomastia in men, and hirsuitism in women. It also may increase the normal testosterone to epitestosterone (T:E) ratio of 6:1, and result in a positive urine test for steroids.

 

Androstenedione has been called a prohormone, because it is one metabolic step from testosterone and estrone (or estradiol) in steroid synthesis. It is said that 50 to 150 mg taken twice daily will raise serum testosterone levels, but in fact it usually only increases estrone and estradiol, with no subsequent gain in strength [18]. Andro became popular in 1998, when Mark McGwire claimed it was responsible for him breaking the Major League Baseball home run record. Don Catlin, MD at UCLAs Drug Control Laboratory felt Mr. McGwire may have used 19-nor-androstenedione, which metabolizes directly into testosterone, or his supplement contained other impurities, such as anabolic steroid (Personal communication, 1999).

 

Creatine

 

Literally hundreds of studies have been done, investigating the ergogenic effect of creatine. In 1835 Chevreul first identified methylguanidine-acetic acid (creatine), then Olexander Palladin later established its role in muscle metabolism. In 1970 Russian scientists demonstrated that creatine increased athletic performance for short duration, maximal intensity exercise, such as sprinting [19]. Creatine is found naturally in meat and fish, but also synthesized from the amino acids arginine, methionine, and glycine in the liver, pancreas, and kidneys. The mean concentration in human skeletal muscle is 125 mmole/kg, with a range of 90 to 160 mmole/kg. In 1994 Greenhaff [20] found that half of his subjects did not eat meat, and consequently had a concentration less than 125 mmole/kg. He suggested that including more vegetarians in a study group, may account for differences noted in efficacy. Dosages of 20 to 30 g/d are effective, with minimal side effects [21]. Creatine monophosphate has been associated with nausea, headache, and other somatic complaints, as well as possible compartment syndrome, muscle cramping, and renal insufficiency. Hydrating the increased stores of phosphocreatine results in water retention, and subsequent increase in muscle bulk. Consequently, we have noticed a greater incidence of soft tissue injuries in our collision athletes, particularly hockey and football players.

 

Chromium

 

Interest in chromium supplementation began when it was discovered that exercise increases chromium loss (probably in sweat). Because it is an essential trace mineral, and a cofactor in the action of insulin, athletes felt that chromium might enhance performance. The average American diet provides 50 percent of the RDA, largely from mushrooms, nuts, whole grains, and prunes. Chromium is so poorly absorbed, that in supplements it is usually bound to picolinate. Theoretically, chromium aids in glycogen synthesis, and enhanced transport of amino acids into muscle cells. In the 1980s, researchers demonstrated anabolic effects in college athletes taking 200 µg/d, who also did resistance training [22]. Recent studies have failed to reproduce those results [23]. Although 50 to 200 µg/d are probably safe, there are anecdotal reports of cognitive impairment, anemia, chromosomal damage, and interstitial nephritis with higher dosages.

 

Metabolic Stimulants

 

These agents attempt to impact strength or speed by either increasing the efficiency of mitochondrial metabolism, or through direct effects on the neuromuscular system. They are some of the oldest ergogenic aids.

 

Pyruvate

 

In the 1980s, pyruvate was found to prevent fatty liver infiltration in rats exposed to chronic alcohol ingestion. Consequently, Ronald Stanko at the University of Pittsburg first investigated pyruvate as a weight loss agent. But because it can be converted to lactate by lactate dehydrogenase, or acetyl CoA by pyruvate dehydrogenase, it occupies the first critical step in oxidative phosphoryllation. He theorized that overloading the system with pyruvate would increase the metabolic rate of cells. Using 75 g dihydroxyacetone and 25 g pyruvate daily, Stanko et al. [24] have published three studies demonstrating increased exercise time to exhaustion in untrained subjects. Unfortunately, many others have failed to replicate those results [25]. The only reported side effects are nausea and diarrhea.

 

Sodium citrate/bicarbonate

 

Alkalinizing agents, such as sodium citrate and bicarbonate may exert their effect on the monocarboxylate transporter, which is responsible for lactate and H ion movement across the muscle cell membrane. Raising the tissue pH has been shown to facilitate ion efflux, and therefore slow the intracellular accumulation of H and lactate, which impair cellular metabolism, and cause fatigue. Performance improved when subjects were given 500 mg/kg sodium citrate 2 hours before a 5-km time trial [26]. Bicarbonate has a very similar mechanism of action, at doses of 300 mg/kg. Effects on performance are variable, with some studies in swimmers demonstrating positive results [27], and others in cyclists showing no improvement [28]. GI distress and possible electrolyte imbalance (from pH changes) are the only known side effects of alkalinizing agents.

 

Sodium phosphate

 

Phosphate loading provides inorganic substrate for ATP and creatine phosphate production, but also may alter the oxygen-hemoglobin dissociation curve by increasing red cell 2,3-DPG (diphosphoglycerate). This has the effect of shifting the curve to the right, which means that there is greater unloading of oxygen at the venous end of capillaries. Stern [29], testing men on a cycle ergometer, showed increased VO 2 max, with improved performance at 10- and 25-mi time trials, using 1.0 g four times per day for 1 week. Because of its effect on the oxygen-hemoglobin dissociation curve, phosphate may provide an additional benefit when working at altitude.

 

Ephedrine

 

Ephedrine is a stimulator of both alpha and beta adrenergic receptors, with direct effect on the central nervous and cardiovascular systems. It improves strength, speed, and endurance, increases mental alertness, and masks the symptoms of fatigue. It also increases metabolic rate, and therefore heat production, which must be dissipated through sweat . In addition to irritability, headache, and tachycardia, other serious side effects including arrhythmias, heat stroke, acute renal failure, and rhabdomyolysis have been reported. The US Food and Drug Administration (FDA) fielded 17,000 reports of adverse events, and attributed 80 deaths to ephedrine or the natural form ma huang, before removing them from the US market in the spring of 2004 [2]. Most notable were the untimely passing of Baltimore Orioles pitcher Steve Bechler (February 19, 2003), and Korey Stringer of the Minnesota Vikings (August 1, 2001).

 

Caffeine

 

One of the oldest pure stimulants, this xanthine derivative is the most widely consumed drug in the world. Taking 9 mg/kg, athletes demonstrate a response similar to ephedrine, for periods of exercise lasting 20 minutes or less [30]. Caffeine may also exhibit a direct effect on skeletal muscle, and improve endurance by prolonging time to exhaustion. Although it does increase plasma free fatty acid levels, several studies have failed to demonstrate any effective glycogen sparing [31]. The usual side effects include headache, irritability, and tachycardia, but Tour de France cyclists using 5 or 10 gm caffeine suppositories, increase the likelihood of serious adverse reactions (Scot Bradley, MD; Personal communication, 2002). Guarana ( paullinia cupana ), and Yerba Mate are said to contain guaranine and mateine, but both of these popular South American stimulants are simply caffeine.

 

Amino Acids

 

Following our discussion of an athlete's protein requirements, it should not be surprising that entrepreneurs have convinced them they need amino acid supplements. The essential amino acids must obviously be consumed in the diet (Table 1), but there are a few others, which may have unique effects on performance.

 

Branched chain amino acids

 

The central fatigue hypothesis maintains that branched-chain amino acids (leucine, isoleucine, and valine) are in equilibrium with tryptophan, which causes fatigue. During prolonged exercise, as glycogen stores are depleted, an athlete begins to metabolize fat and protein. It has been suggested that consuming branched-chain amino acids for fuel creates a relative excess of tryptophan, which crosses the blood-brain barrier, and results in fatigue [32]. Supplementing the diet with 5 to 10 g/d seems to prolong exercise, and has minimal side effects (GI disturbance). Branched chain amino acids are also a metabolic precursor of glutamine , which aids in lymphocyte (immune) function.

 

Arginine

 

Along with ornithine, and lysine, this amino acid has been shown to stimulate the release of HGH. From the previous discussion, it remains to be seen whether or not that effect is e rgogenic. Other attributes of arginine include wound healing and stimulation of the immune system [33].

 

Glutamine

 

Lymphocytes require glutamine for proliferation. Although technically not an essential amino acid, it is synthesized by skeletal muscle, and used for repair of damaged myofibrils. During long sessions of high-intensity exercise, there is not enough glutamine left for lymphocyte production. This may account for Nieman's [34*] findings in studies of exercise and immunity, that moderate activity reduces the risk of infection, while exhaustive exercise makes an athlete more susceptible. In well-controlled trials, which supplemented 500 to 1000 mg/d, the incidence of opportunistic viral infection was significantly reduced [35 * ]. We routinely provide glutamine to our hockey players, who exercise a large muscle group (quadriceps), and often play three games in 5 days.

 

Beta-hydroxy-beta-methylbutyrate

 

At Iowa State University in the 1980s it was discovered that this metabolite of the amino acid leucine had an effect on protein catabolism. High levels of beta-hydroxy-beta-methylbutyrate (HMB) seemed to be protective of muscle protein breakdown, and therefore exhibited a net anabolic effect. The exact mechanism is unknown, but in clinical trials with untrained subjects receiving 1.5 or 3 g/d, there was increased muscle mass and strength in a single-repetition maximum bench press [36]. The natural sources are citrus fruit, catfish, or breast milk, and no significant side effects have been reported.

 

L-tryptophan

 

Although it seems to be a contradiction of the central fatigue hypothesis, tryptophan has been reported to prolong exercise. In 1988 Segura and Ventura [37] demonstrated a 49 percent increase in time to exhaustion when subjects ingested 300 mg, four times per day, prior to exercise. They theorized that tryptophan is a mild analgesic, which reduces the discomfort of prolonged exercise. Unfortunately, those results have never been replicated. Another concern with tryptophan is the report of eosinophilia myalgia syndrome and 32 possible deaths. Although these were believed to be the result of contamination from one Japanese supplier, athletes should exercise caution with this supplement.

 

L-carnitine

 

This amino acid is found in meat and dairy products, also synthesized from lysine and methionine in the liver and kidneys. It increases the transport of free fatty acids into mitochondria, and buffers pyruvate, therefore decreasing the intracellular accumulation of lactate. Although several early studies supplementing 2 to 6 g/d looked promising, more recent work has failed to demonstrate any glycogen-sparing effect [38]. Many supplements available today actually contain D-carnitine, which is inactive in humans, and may actually cause weakness, by competing with the L-isomer.

 

Antioxidants

 

The water-soluble vitamin C (ascorbic acid), and fat-soluble vitamin E (alpha-tocopherol), exert their antioxidant effect by absorbing free-radicals produced during incomplete cellular metabolism. The RDA for vitamin C is 60 mg/d, and inadequate intake can be detrimental. There is recent evidence that megadoses may also adversely impact performance by causing cellular damage [39]. Vitamin C increases urinary oxalate excretion in patients who form calcium-containing stones, and should be used with caution in that group. Alpha-tocopherol at 400 IU/d is better at preventing cellular damage than vitamin C, and is well tolerated at higher doses, unlike the other fat-soluble vitamins.

 

Glucosamine

 

More has been written about glucosamine and chondroitin recently than any other supplement. The observation that glucosamine can stimulate chondrocytes to synthesize collagen and proteoglycans in vitro, was popularized by Jason Theodosakis in his book, The Arthritis Cure [40]. An alternative theory is that glucosamine is simply a centrally acting analgesic. Innumerable studies have been done to test the efficacy in arthritic patients. Currently, the National Center for Complimentary and Alternative Medicine, and the National Institute of Arthritis and Musculoskeletal and Skin Disease (NIAMS/NCCAM) are conducting a large, multi-center, placebo-controlled study. The Glucosamine Arthritis Intervention Trial (GAIT) is a 24-week comparison of glucosamine, or chondroitin, or glucosamine plus chondroitin, or celecoxib (Celebrex(R)) against placebo. They have enrolled 1588 subjects, and will have final data by March of 2005 [41*].

 

Ginseng

 

One of the most widely used alternative medicines in the world, ginseng has been shown to possess beneficial effects as an antioxidant, anti-inflammatory, and potentially anticancer treatment. There are actually several different plants whose roots contain ginsenosides, the most common being Korean or panax ginseng . In addition to the above, it has been claimed to increase mental alertness and athletic performance. Unfortunately, well-controlled studies with the usual doses of 200 to 400 mg/d are not found in the literature [42]. Many of them use ginseng in combination with other vitamins or herbs, making it difficult to draw meaningful conclusions. Side effects include nausea, headache, hypertension, and vaginal bleeding. It also interacts with phenylzine, warfarin, oral hypoglycemics, insulin, and caffeine.

 

Conclusions

 

There is no substitute for proper training, and a sound approach to nutrition. Many athletes, eager to gain an edge on their competition, simply overlook the contribution of a basic diet plan. Although most supplements are safe, both athlete and physician must remember that these are drugs, with side effects and adverse reactions. Because they interact with prescription medications, information about the concurrent use of supplements must be a part of any medical history. Sports medicine physicians must also familiarize themselves with alternative medications and herbal preparations, to better council their athlete patients [43]. An excellent resource is the German Commission E monographs, available from the American Botanical Council (6200 Manor Road; Austin, TX 78723). It contains 380 monographs of 190 different herbs and combinations, with 150 indications for use.

 

Until recently, there has always been an issue of purity. A recent study by the International Olympic Committee revealed that of 240 supplements purchased legally in the United States, 18.8 percent contained prohormones not listed on the label [44]. However, the industry is trying to regulate itself, and in 2003 launched a new Dietary Supplement Verification Program. The FDA and United States Pharmacopeia developed this seven-step testing process to verify that a product meets its label claims of declared ingredients, dosage, and purity. Although voluntary at this time, half a dozen manufacturers including Nature Made (Mission Hills, CA) and Kirkland (Costco(R) brand), who provide 30 percent of all vitamins and minerals (20 percent of the total supplement market) have agreed to participate. Products that meet these standards will be designated "dietary supplement verified" on the label.

 

The moral debate surrounding any form of performance enhancement is beyond the scope of this article. However, athletes must be aware that testing positive for a banned substance carries the same penalty, whether they simply used a dietary supplement or not. When you consider all of the risks, including potential side effects and adverse reactions, using sports supplements is really a modern case of caveat emptor.

 

References and Recommended Reading

 

Papers of particular interest, published recently, have been highlighted as:
* Of importance
** Of major importance

 

1. Bamberger M, Yeager D: Over the Edge: Drug Use in Sports. Sports Illustrated 1997, 86(15): 35.
2.* Ambrose PJ: Drug use in sports: a veritable arena for pharmacists. J Am Pharm Assoc 2004, 44: 501 - 516.
An excellent review with over 100 references.
3. National Collegiate Athletic Association: NCAA study of substance use and abuse habits of college student-athletes. NCAA Committee on Competitive Safeguards and Medical Aspects of Sports. June, 2001.
4.** Clark N: The Athlete's Kitchen. Toronto: Bantam Books; 1986.
One of the best books I've seen on sports nutrition, written for the athlete. Many good recipe ideas, as well.
5. Casa DJ, Maresh CM, Armstrong LE, et al. : Intravenous versus oral rehydration during a brief period: responses to subsequent exercise in the heat. Med Sci Sports Exerc 2000, 32: 124 - 133.
6.** Bentley S: Exercise-induced muscle cramping. Sports Med 1996, 21: 409 - 420.
Excellent review of cramping pathophysiology, and proposed mechanisms.
7. Shi X, Summers RW, Schedl HP, et al. : Effects of carbohydrate type and concentration and solution osmolality on water absorption. Med Sci Sports Exerc 1995, 27: 1607 - 1615.
8.* Lemon PW: Effect of exercise on protein requirements. J Sports Sci 1991, 9: 53 - 70.
These two articles discuss the protein requirements of strength and endurance athletes. Very comprehensive and well written.
9.* Lemon PW, Tarnopolsky MA, MacDougall JD, Atkinson SA: Protein requirements, muscle mass/strength changes during intensive training in novice bodybuilders. J Appl Physiol 1992, 73: 767 - 775.
These two articles discuss the protein requirements of strength and endurance athletes. Very comprehensive and well written.
10. Saunders MJ: Adding protein to sports drink improves performance. Med Sci Sports Exerc 2004, 36: 1239 - 1243.
11. Maffetone P: In Fitness and in Health. Stamford, NY: David Barmore Productions; 1994.
12.** Costill DA: A Scientific Approach to Distance Running. Los Altos, CA: Track and Field News; 1979.
Excellent review of exercise physiology in distance runners.
13. Bergman R, Leach ER: The use and abuse of anabolic steroids in Olympic-caliber athletes. Clin Orthop Rel Res 1984, 198: 169 - 172.
14. Pope HG, Katz DL: Homicide and near-homicide by anabolic steroid abusers. J Clin Psych 1990, 51: 28 - 31.
15. Voy R, Deeter KD: Drugs, Sports, and Politics. Champaign, Illinois: Leisure Press; 1991.
16. Yarasheski KE, Zachweija JJ, Angelopoulos TJ, Bier DM: Short-term growth hormone treatment does not increase muscle protein synthesis in experienced weight lifters. J Appl Physiol 1993, 74: 3073 - 3076.
17. Yen SS, Morales AJ, Khorram O: Replacement of DHEA in aging men and women: potential remedial effects. Ann NY Acad Sci 1995, 774: 128 - 142.
18. King DS, Sharp RL, Vukovich MD, et al. : Effect of aral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial. JAMA 1999, 281: 2020 - 2028.
19. Kalinski MI: State-sponsored research on creatine supplements and blood doping in elite Soviet sport. Perspect Biol Med 2003, 46: 445 - 451.
20. Greenhaff PL Puffer CJ: The use of drugs in swimming. Clin Sports Med 1986, 5: 77.
21. Greenhaff PL, Casey A, Short AH , et al. : Influence of oral creatine supplementation on muscle torque during repeated bouts of maximal voluntary exercise in man. Clin Sci 1993, 84 :5 65 - 5 71.
22. Hasten DL, Rome EP , Franks BD et al. : Effects of chromium picolinate on beginning weight training students. Int J Sport Nutr 1992, 2: 343 - 350.
23. Hallmark MA, Reynolds TH, DeSouza CA, et al. : Effects of chromium and resistance training on muscle strength and body composition. Med Sci Sports Exerc 1996, 28: 139 - 144.
24. Schifke AC: Can pyruvate and dihydroxyacetone (DHAP) improve performance? Nutrition Bytes 1999, 5: 1 - 5.
25. Morrison MA, Sriet LL: Pyruvate ingestion for 7 days does not improve aerobic performance in well-trained individuals. J Appl Physiol 2000, 89: 549 - 556.
26. Oopik V, Saaremets I: Effects of sodium citrate ingestion before exercise on endurance performance in well trained college runners. Br J Sports Med 2003, 37: 485 - 489.
27. Gao JP, Costill DL, et al. : Sodium bicarbonate ingestion improves performance in interval swimming. Eur J Appl Physiol Occup Physiol 1988, 58: 171 - 174.
28. Horswill CA, Costill DL, Fink WJ, et al. : Influence of sodium bicarbonate on sprint performance: relationship to dosage. Med Sci Sports Exerc 1988, 20: 566 - 569.
29. Stern RA: Effects of sodium phosphate loading on 10 mile cycle time trial performance. University of Brighton 1998, Unpublished thesis.
30. Graham TE: Caffeine and exercise: metabolism, endurance, and performance. Sports Med 2001, 31: 785 - 807.
31. Bell DG, Jacobs I, Ellerington K: Effect of caffeine and ephedrine ingestion on anaerobic exercise performance. Med Sci Sports Exerc 2001, 33: 1399 - 1403.
32. Williams MH: Facts and fallacies of purported ergogenic amino acid supplements. Clin Sport Med 1999, 18: 633 - 649.
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