Natural Foods Merchandiser

The science of sports supplements

Anyone observing elite athletes soon understands that ?pushing the edge? is simply their way of life. In recent times, however, it has become common for young athletes and even weekend warriors to try to surpass their own records. Although many options exist for performance enhancement, there is one method shared by many: the use of sports supplements. In 2003, sports nutrition supplement sales grew 8 percent to $1.97 billion.1 To help inform sports enthusiasts, a review of some of the more popular sports supplements follows—noting their ingredients, uses and scientific support.

Creatine: the ?old? versus the ?new?
Creatine monohydrate is typically referred to as just creatine. It is a naturally occurring amino acid synthesized in major organs and then stored as phosphocreatine—primarily in skeletal muscle.

Introduced as a sports supplement in 1993, its ingestion was believed to enhance performance by increasing the amount and availability of PCr in muscle cells.2 Theoretically, the more PCr in a muscle cell, the faster energy is resynthesized in the form of adenosine triphosphate, powering high-intensity exertion as well as helping mediate muscle fatigue between exertions.

Hypothetically, any extra creatine-assisted work an athlete is able to do results in greater gains of strength, mass and/or performance, benefiting athletes such as weight lifters and sprinters.2,3 Such gains have been noted in persons after very short periods of CrM supplementation, suggesting that effects can be achieved independent of prolonged training.4 CrM supplementation, however, has not been shown to improve performance for sustained, submaximal efforts such as middle- or long-distance running.5

Hundreds of studies have examined CrM?s effects on trained and untrained athletes as well as various populations suffering from disease. Although most research shows statistically significant improvement in exercise capacity, researchers have found greater performance enhancement in those who had very low initial CrM stores (i.e., vegetarians or patients with muscular diseases) than in trained athletes.3,6,7 In athletes, positive performance results have been achieved by loading muscle stores during training periods with 15 g to 30 g per day for five to seven days, followed by 5 g/day for maintenance6—although a more recent study questions the assumption that 5 g/day is sufficient for maintenance.8

The safety of long-term, low-dose CrM supplementation (five days initially at 15.75 g/day, followed by an average 5 g/day) was examined in a recent study of 98 college football players whose health was monitored for 21 months. Biomarkers were used to compare the health of subjects who used CrM for varying periods of time versus a control group that did not. Researchers reported that CrM did not appear to adversely affect the clinical status of health markers.9

Another three-year study followed college football players to examine the incidence of cramping and/or injury in players using CrM. Results indicated that supplemented players did not appear to be at increased risk for injuries as defined in the study.10 Despite such systematic evidence, CrM still has been implicated in instances of weight gain, diarrhea and muscle cramps, although without apparent scientific substantiation.6

CrM is not recommended for users who have not completed puberty; the science simply cannot support it.2 An interesting note, however, is that several long-term studies with infants suffering from metabolic diseases that inhibit the natural manufacture of body creatine reported notable efficacy for a period of several years. No adverse effects were reported using daily doses equal to double the loading dose used for adults (expressed per pound of body weight).11,12

Two issues are important to the CrM consumer. First is the well-substantiated concern about product quality: Only supplements using U.S. or German pharmacological-grade sources appear to be without impurities.2 Second is a need for understanding the difference between old and new (or enhanced) products.

To understand old CrM, science tells us that 95 percent of dietary CrM is absorbed through the small intestine directly into the blood and transported into muscle cells as needed.2 Unused CrM is simply excreted in the urine (not passed through the intestinal tract as often declared).2,13 CrM absorption from the intestines may be influenced by the body?s mineral concentrations (equal amounts of sodium and chloride with low concentrations of potassium favor transport), while CrM uptake by muscle appears to be profoundly influenced by blood concentrations of insulin (higher insulin increases uptake).14,15

Seeking to expand understanding, two studies examined the effects of enhancing CrM supplementation by creating high concentrations of blood insulin (with insulin injection or consumption of either 90 or more g of sugars or some 50 g sugars plus 50 g proteins). Both studies resulted in measurably improved muscle/whole body CrM retention. However, the findings showed that such retention could be achieved only when insulin was present at remarkably high concentrations and most probably would be effective only during the first 24 hours after supplementation.16,17 A review of CrM science conducted in 2000 recommended ingestion of a 95-g carbohydrate drink or a combined 50- to 80-g carbohydrate and 30- to 50-g protein drink to enhance CrM uptake.4 (Although nutritional needs are individualized by sport and competitor, one nutritional textbook suggests, for comparative purposes, that a total daily intake of 477 g to 795 g of carbs and up to 128 g of protein would meet the needs of a 175-pound male athlete.18)

More recently, a pilot study comparing three new enhanced formulations of CrM indicated it took only 18 g of dextrose (equal to 18 g of carbohydrates) ingested over three days to augment whole-body CrM retention.18,19 Further investigation of such enhanced CrM products offering carbohydrate and/or protein additives appears warranted when considering this pilot study?s confounding findings, especially since CrM appears to affect performance in the short term only.

Studies examining other enhanced products have produced essentially the same, or worse, results as old CrM. Effervescent creatine citrate is a patented compound of creatine, biocarbonate and citrate salts. It is marketed as a method of encouraging faster CrM movement from the stomach into the small intestine; however, the former pilot study revealed that EC was no more effective than ingestion of CrM alone.19 Creatine serum versus powder to improve cycle sprint performance was also studied, and the serum was found to be less effective than the powder.20 Another study showed that ingestion of the serum produced no change in blood CrM concentrations—an indication of CrM absence.21

One more promotion, creatine ethyl ester, is also quite controversial. Claiming that CrM is not well absorbed through cell walls—despite abundant evidence to the contrary—the products are marketed as superior to old CrM because they carry an esterified creatine into the cell via fat (an abundance of which is, ironically, lacking in trained athletes).13,22,23 To date, there do not appear to be any controlled human studies comparing creatine ethyl ester to CrM that would prove the claim.

While science has substantiated our current understanding of CrM absorption, the market appears to be romping far ahead of science in its promotion of enhanced CrM varieties. Research has yet to support claims for these new compounds.

Rhodiola rosea
Rhodiola rosea, also known as golden root or arctic root, has been used and documented extensively since the mid-1700s in the traditional medicines of China, Russia and Scandinavia. Some 180-plus studies of the marker compounds associated with its effectiveness (rosavin and salidroside) have been conducted (and published primarily in Slavic and Scandinavian languages) since 1961.24

Defined as an adaptogen (an herb affecting the hypothalamic-adrenal axis and, thereby, improving the body?s ability to respond to stress), Rr is effective in helping the body normalize when subjected to chemical, biological or physical stressors.25 Researched globally in humans and animals, a recent human study suggests that Rr extract may enhance endurance exercise performance with a single dose, an effect not seen among the more familiar adaptogens.24,26 Coping with mental or physical stressors requires flexibility of both the mind and body, and Rr has been shown to assist that adaptation quickly. A 2003 study on a group of 161 cadets produced profound antifatigue effects while measuring mental work.27 Another review of original Russian studies reported that Rr increased the swimming time of rats subjected to a ?to the limit? study by 135 to 159 percent.13

Western interest in Rr piqued shortly after discovering that Russian researchers had extensively researched its ability to provide their athletes an edge in global competition during the Cold War.24,28 Recent studies conducted in the United States, however, with Rr alone or combined with cordyceps (Cordyceps sinensis, a fungus long used in Chinese medicine as an adaptogen), have shown no performance-enhancing effect.29,30

Although language barriers have complicated English-speaking researchers? abilities to verify claims, enough understanding of the plant?s history and use exists to encourage further inquiry. Evidence validating the use of Rr as a performance-enhancing sports supplement has yet to be collected from Western researchers, although it does appear to offer some cardio-protective benefits.25

Beta-hydroxy-beta-methylbutyrate, or HMB, forms naturally in the body when leucine, an amino acid component of protein, is broken down. Allowed by the International Olympic Committee, its popularity among athletes is based on the theory that supplemental ingestion of amino acids will increase muscle mass.31Although definitive studies have yet to be performed, the supplement is claimed to mediate muscle breakdown resulting from strength training.32

A survey of nine HMB studies showed that HMB significantly increased net lean mass by 0.28 percent per week and strength by 1.40 percent per week. 33

Notable is that one of the authors of this survey owns a company marketing HMB supplements.33 In fact, other literature concludes that such benefits are not replicated in strength-trained individuals.34,35

And yet, HMB has been found to mitigate markers of muscle damage in long- distance runners,36 and two other studies found an unanticipated ability to reduce blood pressure and cholesterol levels. In addition, these studies supported safety claims with measurements of selected blood biomarkers and liver and kidney functions.31,37 Lastly, research seems to substantiate HMB?s ability to burn fat and build lean muscle among individuals who are not already physically fit.37

Essential amino acids
Of the 20 amino acids required for protein building, an adequate diet provides nine of the essential amino acids and allows the body to manufacture the eleven remaining nonessential amino acids as needed.

Because nutrition is often the defining factor between winning and losing among trained athletes, the importance of maintaining adequate EAA levels cannot be overstated.38 A recent study showed that ingestion of EAAs one to two hours after resistance training was twice as effective as ingestion of a combined EAA-NEAA for acute stimulation of net muscle protein.33,39,40

A 1998 study, focusing on the elderly, supported the theoretical link between an adequate supply of EAAs and increased muscle protein synthesis. Results showed that any loss of muscle mass associated with aging is most probably linked to an inadequate diet rather than any inherent inability of the body to use EAAs.41

In short, the science shows a healthy nutritional strategy underlies the process for adding or maintaining muscle mass in both the trained athlete and the elderly. A serious question remains for science to answer: Which produces the greatest performance and/or muscle mass gains over the long term, EAA supplementation or whole protein ingestion?

Nitric oxide
Promoted to resistance trainers, NO2 (called nitric oxide) is actually a supplement that stimulates nitric oxide. It is composed of arginine chemically connected to alpha-ketoglutarate. Nitric oxide itself is naturally produced in various body tissues and affects blood flow as well as oxygen and muscular glucose uptake.42,43

To date, however, only one study has examined the effects of AAKG supplementation on issues of interest to the athlete. Results demonstrated that large doses may increase by one the number of bench press repetitions during a maximum strength effort and increase sprint peak power for training athletes but will not significantly affect body composition, endurance, fat loss, muscle pump or sexual function as originally promoted.44 The bottom line: Until more research can dispute these results, resistance-training athletes probably shouldn?t rely upon this supplement to augment training goals.

Summing it up
Although science has given athletes a useful body of knowledge in areas of nutrition and performance, research about supplements for performance enhancement is still in its infancy.45 This short review has highlighted the efforts of researchers pushing their own edge—seeking to discover whether or not the more popular sports supplements actually work.

Kathryn Montgomery is a Denver-based freelance writer. She may be reached at [email protected]

Keep an eye on supps? methods and marketing
Athletes with an eye for science can benefit from a discussion of how marketing promises are measured. With support, in part, from the foods industry, new measurement techniques for numerous physiological states have been developed, including muscle or fat mass, glycogen depletion, fat-oxidation rates, gastrointestinal distress and muscle damage.45 A review of commonly used biomarkers found, however, that some of the test methods might actually confound findings. For example, measuring muscle mass by muscle circumference can be unreliable due to the level of subcutaneous fat, or even glycogen or water content.46 The real answer to ?Does it work?? may be found by assessing exactly what questions were asked and what measurements were made to find out how the supplement works.


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42. [No authors listed] NO2.
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Natural Foods Merchandiser volume XXVI/number 5/p. 42, 44

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