THE SCIENCE OF SPORTS AND FITNESS NUTRITION

THE SCIENCE OF SPORTS AND FITNESS NUTRITION

by Steve Myers

See Also: Related Article L-Carnitine

Sports and exercise have become very scientific. Professional athletes as well as weekend warriors are relying heavily on scientific research to help them run, stretch, swing, hit, pedal, position and lift better. One of the biggest impacts of science on sports and fitness has been in the area of nutrition. Most people with active or athletic lifestyles have transcended mere whole foods nutrition and have entered into an era of increasingly scientific sports nutrition, the foremost of which is supplementation.

Getting stronger, generating more energy, improving recovery and enhancing performance have become specific target goals, and supplements and ingredients have focused on the physiology of various aspects of exercise and fitness. In the process, the greater sports and fitness community is more in tune with how athletes prepare, endure and recover from workouts. Along the way, research has answered questions about such physiology and related products. Scientific work in this area has also posed new questions and challenges to sports nutrition.

Research, and calls for more research, have exploded in the sports community in the last few years. With many supplements growing in popularity, especially in the wake of pro athlete endorsements and/or use, fiery debates have erupted over the efficacy and safety of most sports supplements. As is often the case with dietary supplements, the science and research can hardly keep up with the information and proof demands of the medical industry and the greater public. But research continues to surface and provide useful information on certain facets of sports and fitness.

While scientific study now permeates most areas of exercise physiology, the largest concentrations center on increasing energy, building strength and power, losing excess body fat, improving recovery, preventing and addressing injuries, and optimal nutrition during workout.

Energy Crisis?

Energy could well be the root of exercise. How many people fail to initiate or maximize exercise because of a perceived lack of energy? Though important to get things going, energy is crucial to all stages of exercise and, as such, is one of the biggest concerns of active people at all levels.

The basic physiology behind energy production, storage and use is well known. The focus of energy production in the body is focused on adenosine triposphate (ATP), which is often called the energy currency of the body. ATP is comprised of adenine nucleotide and two other phosphate groups. It stores energy in covalent bonds between the phosphates and releases energy when enzymes cause ATP to lose one of its phosphate components. In the end, ATP produces adenosine diphosphate (ADP), inorganic phosphate and, most importantly, energy that can be used for biological functions, including exercise. Thus, ATP levels are key to available energy.

Creatine is the bedrock product in modern sports nutrition. Creatine is a protein found naturally in the body and is obtained from red meat. It is available in popular supplement form at higher concentrations than found in meat. Like a rechargeable battery, ATP can be depleted and must be produced again to continue providing energy for muscle contraction. According to Ray Sahelian, M.D., author of Creatine: Nature's Muscle Builder, this depletion happens very quickly (10 seconds), but creatine phosphate gives its phosphate molecule to the ADP for recreation of ATP. He reported, "This greater ATP synthesis also keeps your body from relying on another energy system called glycolysis, which has lactic acid as a byproduct." According to Dr. Paul Greenhaff from the University of Nottingham in England, creatine also shuttles energy from the mitochondria where ATP is being produced to the myofilaments where contraction is in progress.

The popular way to use creatine is via a loading process, which saturates the muscles with the substance and, thereby, promotes quicker energy restoration. More than 150 clinically controlled trials have proven the performance benefits associated with creatine supplementation. Research on creatine has shown that the supplement can increase the amount of work performed by healthy subjects. Creatine has also been shown to facilitate muscle phosphocreatine resynthesis during recovery from intense exercise.

A recent study led by Dr. F. Vandebuerie of the Exercise Physiology Laboratory in Leuven, Belgium, showed that creatine loading improved sprint cycling after endurance exercise. This effect did not occur with additional creatine intake during exercise. (Internat J Sports Nutr, 19:490-495, 1999.) One Spanish study did find, however, that creatine supplementation improved performance during exercise. Researchers from Madrid and Barcelona showed that cyclists taking 20 grams of creatine monohydrate for five days increased the capacity to maintain high intensity sprint training by almost 20 percent. (Med Sci Sports Exer. 32:379-385, 2000).

The revolving and overriding concern with creatine has been about potential side effects. A controlled study by Mark Tarnopolsky at McMaster University in Canada found that 20 grams of creatine daily for five days increased fat-free weight and total weight without increasing blood pressure, kidney damage markers creatine kinase and creatinine (Med Sci Sports Exer; 32:291-296, 2000). The studies on creatine and performance during and after exercise are ongoing. As more results surface, most questions about the benefits and side effects of creatine will be answered.

One component of the adenine nucleotide found in ATP is ribose, a 5-carbon monosaccharide (sugar). It, therefore, is an integral factor in energy production. Ribose is formed when glucose travels through the Pentose Phosphate Pathway (PPP) and undergoes a chain of metabloic reactions. Then, as the cellular nucleotide pool is decreased by lack of oxygen to the cell, 5-phosphoribosyl-1-pyrophosphate (PRPP), a physiological form of functional ribose, is needed to restore lost energy compounds. Supplemental ribose reportedly bypasses slow enzymatic reactions and goes directly to PRPP for production of nucleotides need to produce ATP.

A study conducted at Eastern Michigan University (EMU) investigated whether short-term, oral ribose supplementation improved anaerobic power in eight young men during strenuous exercise. The results demonstrated that oral ribose supplementation may affect peak and mean power during repeated cycle sprints in men. Also, a German study, published in the Aug. 29, 1992 issue of the Lancet, confirmed that ribose normalized ATP levels during recovery from exercised-induced ischemia.

Ed Burke, director of exercise science at the University of Colorado in Boulder, reported that ribose is a very well studied product and noted that more than 100 papers have been completed or published on its benefits. He added that more human studies are underway, and researchers are finding that, despite its initial role as a recovery aid, ribose can have an impact even during exercise.

Muscle recovery from depletion is the goal of Jogmate, a nutritional bar produced by Mission Hills, Calif.-base Pharmavite Corp. "Just after exercise, muscles take in a large amount of protein," explained Chris Evans, a company nutritionist. "JogMate works by increasing glycogen and decreasing protein breakdown." However, the bar needed scientific backing to accompany its special blend of protein, carbohydrates and essential vitamins and minerals. Mission Hills, Calif.-based JogMate manufacturer Pharmvite subjected JogMate to two university studies.

One trial conducted at Boston University demonstrated that Jogmate enhanced muscle glycogen resynthesis following prolonged exercise. The other study, conducted at Vanderbilt University, discovered that JogMate increased plasma glucose and amino acids, and it enhanced leg glucose uptake. The results also showed that the bar improved recovery of leg protein stores immediately after exercise. "Our research proves that consuming JogMate protein immediately after exercise increases muscle protein storage in the legs and allows for faster recovery of leg muscle and glycogen stores," confirmed Paul Flakoll, Ph.D., associate professor at Vanderbilt and primary study investigator.

Strength

One of the biggest goals in exercise is building muscle. To this end, testosterone is the crucial element. Anabolic steroids that increase testosterone made big news for years, as athletes craved the extra edge it provided. Unfortunately, grave side effects such as shrinking testicles, impotence, enlarged prostate and major organ failure arose, driving a quest to discover natural testosterone boosters.

Shortly after the passage of the Dietary Supplement Health and Education Act of 1994 (DSHEA), DHEA (dehydroepiandrosterone) drew attention from body builders for its potential to boost testosterone levels. This pro-hormone is produced by the adrenal glands just before puberty and reaches peak levels in a person's mid 20s. These levels diminish from 30 years of age until about 80 years. DHEA is converted in the body to androstenedione and then testosterone, but many experts contended that young men naturally produced enough DHEA to maintain optimum testosterone levels and, therefore, did not need DHEA supplementation. Furthermore, there is a lack of scientific study on DHEA and athletes and body builders. It has since become more popular in the older population, those aging baby boomers whose DHEA levels are tapering off.

The major attention in testosterone boosting alternatives has been on androstenedione (commonly referred to as andro). This precursor to testosterone is a vital factor in male reproductive function and tissue generation. Similar to levels of most androgenic hormones, production levels of andro fluctuate depending on age, gender and health status, but the average man reportedly makes about 3 mg of andro daily. Based on its role as a precursor to testosterone, andro was believed to increase muscle strength and size.

Andro made major headlines when big league slugger Mark McGwire broke a home run record during the 1998 baseball season in which he took an androstenedione product. The market for andro products instantly exploded following the Mark McGwire "endorsement." Along with the sales boom, intense scrutiny and criticism mounted, as amateur and professional athletic organizations reiterated bans on andro, and cable sports network ESPN pulled Met-Rx commercials for andro products. The sticking points were not dissimilar to other areas and products in the dietary supplement industry--a lack of sufficient scientific study on the benefits and possible side effects of the supplement.

A serious blow came when the June 2, 1999 issue of the Journal of the American Medical Association (JAMA) published the results of a study that showed that andro may not increase muscle size and strength and may also have adverse side effects. Sports nutrition experts, such as Tim Ziegenfuss, Ph.D., assistant professor of exercise science at EMU, attacked the validity of the JAMA study. Ziegenfuss, who spent most of 1998-1999 researching andro supplements for increased muscle strength and size, criticized the JAMA study's use of subjects who were not practiced weight trainers. He noted that all men new to weightlifting tend to gain substantial muscle just from the new activity alone, an occurrence that might have overshadowed the effects of andro. He further said that the drop in HDL (good) cholesterol reported by the study's researchers was within what are considered to be normal levels. The study also failed to mention the resulting ratio of total cholesterol to HDL, which is the usual marker of cardiovascular risk. Furthermore, the andro supplement used in the study was reported to be 300 mg of pure androstenedione, but the research authors originally noted in an abstract of the study that the subjects were given the andro as well as DHEA, tribulus terrestris, chrysin, indole-carbinol and saw palmetto. Ziegenfuss questioned, "Was it the androstenedione that exerted the [side] effects, or was it the other ingredients or some combination of the two?"

Ziegenfuss has led his own studies on adrenal androgens. Conducted at the Laboratory of Applied Physiology at EMU, the placebo-controlled, double-blind clinical trials involved physically active adult men given Androstat 6 Popper, a product manufactured by Hicksville, N.Y.-based Bodyonics Inc. In one study, the andro supplement led to increases in peak testosterone values (98 percent above baseline) at 40 minutes of supplementation. These upper levels diminished from that point to baseline levels at 180 minutes. The results showed that acute administration of andro can significantly elevate plasma testosterone levels in men but does not seem to have anaerobic, ergogenic effects or influence autonomic nervous system function. Another EMU study demonstrated that the men taking the andro supplement experienced increases in body mass, fat-free mass and vertical leap. The results showed that four weeks of andro supplementation may cause anabolic, ergogenic changes in men without any negative changes in serum lipoproteins, organ function or reproductive hormones.

Such research as that conducted by Ziegenfuss reflects the developments in the andro product market. The Andro 6 Poppers used in the studies consist of a blend of androgen, including androstenedione, androstenediols and 19-nosteroids. "The reason why there are so many different forms of andro on the market is because each has its own claimed effects," explained Ziegenfuss. He explained that the small difference in where the chemical bond is located--whether the bond is located at the four or five position--makes for a four- or five- dione or diol. The 19-norandro derivative means there is no carbon in the nineteenth position. "The bottom line is that each derivative has its own claimed effect. Dione in and of itself is not an effective testosterone booster; if you do get any amount of increase from 4-dione, you get about double or triple the amount of estrogen." He noted that 19-norandro helps achieve a lean, tone muscular look, whereas 4-diol or 4-diol blend can help a person get big and strong fast.

While the different sides struggle to sort out the efficacy and safety of androstenedione and its many derivatives, a new zinc-magnesium supplement has surfaced as a contender in the quest for testosterone boosts. ZMA™, developed by Balco Labs, is a highly specific vitamin-mineral combination that has been shown to enhance athletic performance and testosterone levels. In a study published in the November 1998 issue of Sports Medicine, Training and Rehabilitation, ZMA, comprised of zinc, magnesium (both chelated) and vitamin B6, was found to increase free and total testosterone levels by more than 30 percent when taken nightly.

Micro-mineral zinc in ZMA is involved in the action of insulin, growth hormone, testosterone and estrogen, according to Rehan Jelali, president of the Supplement Research Foundation. It is involved in more than 200 enzymatic reactions. Similarly, the micro-mineral magnesium is involved in some 300 enzymatic reactions, including glycolis, the Krebs cycle, creatine phosphate formation, nucleic acid synthesis, amino acid activation, cyclic AMP formation and protein synthesis leading to greater strength in athletes. Further affecting protein synthesis is vitamin B6, the coenzyme form of which is heavily involved in amino acid metabolism. Additionally, it releases carbohydrate energy.

Another new kid on the block is velvet antler, a nutrient derived from the exterior bone formations of elk and deer antler. Preliminary results from a recent study conducted at the University of Alberta (UA) in Canada found that city police recruits and UA football players taking velvet antler showed five or six times their normal testosterone levels. This was as much as if they had taken anabolic steroids (the antler taken had tested free of such steroids, however.) Consequently, Arkady Koltun, M.D., Ph.D., chairman of the Russian Medical Committee for the Russian BodyBuilding Federation, reported that Russian kayakers, bodybuilders, weightlifters and powerlifters given velvet antler experienced increased muscular and nerve strength. As with most sports nutrition ingredients, research on velvet antler is forthcoming, with most of the research originating in Canada and New Zealand.

Damage Control

Intense exercise is hard on the body. The bones, joints and ligaments can suffer a great amount of stress, especially as nutrient and energy depletion increases. The problem has become a great concern--Baby Boomers, in their pursuit of fast-escaping youth, logged more than one million sports injuries in 1998, according to the U.S. Consumer Product Safety Commission (CPSC). They spent nearly $19 billion on emergency and follow up care for these injuries. For this reason alone, cheaper, natural alternatives that can help prevent injuries and medical visits are becoming more popular components of modern physically active lifestyles.

Whether running or enduring any number of other impact activities, bones and joints take some of the worst beatings. The parts of the body involved in bone and joint injuries include ligaments, tendons and cartilage. Such tissue is comprised of collagen, and glycosaminoglycans (GAGs), which are long chains of sugars. GAGs and collagen are responsible for the building and rebuilding of the bone and joint components. While the body naturally makes glucosamine from glucose and glutamine and also converts glucosamine to GAGs, such production is insufficient in the wake of a connective tissue injury. Also, the body's glucosamine production weakens as a person ages. For these reasons, one of the most prized nutritional supplements for bone and joint health is glucosamine sulfate, especially when combined with chondroitin sulfate.

Glucosamine is easily and quickly absorbed at a high percentage--it is 98-percent absorbable. The small molecules of glucosamine penetrate the cartilage and aid in the production of the proteins necessary for optimal cartilage health. In one study, 51 young male athletes and 17 young female athletes with cartilage damage of the knee (a common sports injury) took 1,500 mg of glucosamine sulfate daily for a total of 40 days, after which they took 750 mg daily for the next 90 to 100 days. Researchers discovered that in 52 of the athletes, symptoms were erased and full athletic training was resumed. A 12-month follow-up of these patients showed no indications of cartilage damage.

Glucosamine is a precursor to chondroitin, which is one of six GAGs. Along with two other GAGS, chondriotin is sulfated and carries a negative charge. These sulfated GAGS repel each other and attract water. These actions help fill space and absorb shock, which protects the bones and ligaments.

While criticizing the supplement industry for exaggeration of the effects of glucosamine and chondroitin, a meta-analysis of relevant studies reported in the Mar. 15, 2000 issue of JAMA (McAlindon, T et al. 283(11):1469-75) that "trials of glucosamine and chondroitin preparations for osteoarthritis symptoms demonstrate moderate to large effects" and "some degree of efficacy appears probable for these preparations."

In addition to cartilage building aids, anti-inflammatory products also have garnered praise from sports enthusiasts. Methylsulfonylmethane (MSM) has been shown to improve recovery from sports-related injuries. A preliminary study conducted at the University of California in Los Angeles (UCLA) and sponsored by Greenville, Pa.-based Carolwood Corp. (using its trademarked Lignisul MSM) examined the effects of the sulfur-rich MSM on 24 men and women who had suffered athletic injuries. Results showed that 58 percent of these patients experienced "significant recovery" after taking the supplement. There were also 40-percent fewer doctor's office visits recorded in the same group.

Fat Patrol

The biggest motivator behind exercise and athletics is to look better, which most often means losing excess fat or weight. The weight loss category of dietary supplement market has been in a continuous growth phase, as new weight control products pop up every month. The most popular area of weight loss products is thermogenesis, the burning of unwanted or unnecessary calories. Likewise, the most talked about supplements in this group include ephedra, chromium picolinate (see  column on Thermogenesis, ) and Citrus aurantium.

Zhi shi is the immature, dried fruit of Citrus aurantium, commonly referred to as bitter orange. This herb was traditionally used in Chinese Medicine for improvement to a number of body functions, but it has been most recently lauded for its thermogenic properties. Preliminary research has shown this herb to possess a triad of benefits for the sports and fitness community--it helps burn fat, increase physical performance and build lean muscle mass. Advantra Z™, a product of Fairfield, N.J.-based Nutratech, contains a composition of five adrenergic amines, according to Dennis Jones, Ph.D., holder of Advantra Z patents and researcher of natural weight loss and fitness ingredients. He reported that the bitter orange ingredient increases metabolic rate with out affecting heart rate or blood pressure by stimulating beta-3 cell receptors. The ingredient prompts the release of adrenaline and noradrenaline in the vicinity of the beta receptor sites commonly found in adipose (fat) tissue and the liver. The stimulation of the beta-3 receptors elicits lipopysis, the breakdown of fat, while helping to burn calories via increasing the metabolic rate.

In the March 1999 issue of Current Therapeutic Research, study results showed that Citrus aurantium combined with St. John's wort and caffeine promoted both body weight and fat loss in overweight adults. (Carlon, M. et al. 60:145-153). A more definitive study was conducted by researchers from the McGill Nutrition and Food Science Center at the Royal Victoria Hospital. The results suggested that bitter orange supplementation in lean patients led to an increased thermogenic response and a measurable increase in metabolic rate. An Italian study showed that Citrus aranthium led to a reduction in the consumption of food and body weight gain in rats (Calapai, G. Effect of Oral Administration of Extract of Citrus Auirantium on Rats, 1998).

L-Carnitine - The Ideal Workout Companion

by Paula Gaynor, Ph.D.

The sports nutrition marketplace is constantly bombarded with new products that are marketed to enhance exercise performance. While some products genuinely do help, often they have no effect, and eventually disappear from the marketplace. But unlike products that come and go, L-carnitine, a vitamin-like nutrient found naturally within the human body, has been available as a dietary supplement for 20 years. Backed by sound and extensive clinical research and a solid safety record, L-carnitine is a workout companion supplement that is here to stay. Why? Following are the top ten reasons, though unlike David Letterman's list, these are not in order of importance.

1. L-carnitine functions in ensuring the production of energy from fat. This physiological function of L-carnitine is critical during exercise because fat is one of the two main fuels used to provide energy for physical activity (the other being carbohydrate). L-carnitine binds to fatty acids and shuttles them into the mitochondria (the "powerhouse of the cell") where they can subsequently be broken down to produce energy.

2. Clinical research indicates that L-carnitine supplements may be of value in people striving for improved exercise performance. Whether training for competition or simply exercising to keep fit, the key lies in reaching the ultimate goal of optimized exercise performance. L-carnitine supplementation (2 g/day) has been found to increase peak treadmill running speed by an average of 5.7% in marathon runners. A number of studies have also found that L-carnitine supplementation helps to increase VO^₂max in both "weekend warriors" and endurance athletes. Exercise physiologists traditionally use this parameter, VO^₂max, as the yardstick to measure the capacity for endurance exercise.

3. L-carnitine supplementation may delay the onset of fatigue during exercise. It does not take a rocket scientist to realize that fatigue during exercise is undesirable as it ultimately compromises performance. Two key causes of fatigue during exercise are lactic acid accumulation and glycogen (a form of carbohydrate) depletion. At least three clinical studies, involving moderately trained and highly trained individuals, have shown that L-carnitine supplementation can reduce lactic acid accumulation. Research also indicates that L-carnitine supplementation leads to increased utilization of fat during exercise and an accompanying glycogen sparing effect. Net result? Delayed fatigue onset and improved exercise performance.

4. L-carnitine supplementation alleviates a painful recovery. Clinical research indicates that in untrained people, L-carnitine supplementation can reduce muscle pain and tenderness and decrease muscle damage caused by unaccustomed exercise. This protective effect of L-carnitine is thought to be due to its ability to deliver more blood--and hence more oxygen--to the muscle during the early stages of exercise, thereby improving energy metabolism.

5. Exercise leads to increased losses of L-carnitine in urine. This loss may be followed by a decrease of L-carnitine in the active muscles, which may not always be rapidly replenished; therefore, L-carnitine supplementation may be warranted to compensate for this loss.

6. L-carnitine supplementation increases blood levels of L-carnitine and prevents the drop in blood L-carnitine levels caused by exercise. It is well documented that during workout sessions, there is a decrease in free L-carnitine levels in the blood. This is significant because it may limit the use of fat as an energy source. L-carnitine supplementation causes a rise in blood L-carnitine levels and also prevents the decrease that is caused by exercise. Researchers conclude that the elevated blood L-carnitine levels without a decrease after strenuous exercise in well-trained athletes is important in view of the effects of L-carnitine in improving skeletal muscle performance.

7. Supplementing with L-carnitine during exercise has the additional benefit of helping to support healthy heart function. Exercise, while ultimately beneficial for the heart, increases the workload of this vital organ. Because L-carnitine ensures the production of energy from fat, and the heart derives most of its energy from fat breakdown, this is a key supplement for maintaining cardiovascular health.

8. L-carnitine supplementation plays a role in reducing body fat. Clinical studies have shown that L-carnitine, in conjunction with exercise and calorie restriction, is helpful in lowering body fat. According to Debbi Lawrence, two-time U.S. Olympian and holder of world and U.S. records in the sport of racewalking, L-carnitine supplementation increases her energy levels during exercise and has reduced her body fat. Lawrence supplements with 2.5 to 3 g L-carnitine L-tartrate daily, marketed under the brand name L-CARNIPURE^®.

9. Athletes may lack L-carnitine due to reduced internal synthesis or dietary choices. Humans have two sources of L-carnitine--biosynthesis in the body and dietary intake. Internal biosynthesis of L-carnitine involves the amino acids lysine and methionine, as well as niacin, iron, and vitamins C and B6. However, athletes are frequently deficient in iron, vitamin B6 and lysine, thus reducing L-carnitine biosynthesis. In the case of food intake, L-carnitine is found primarily in animal products. Consequently, for vegetarians and particularly vegetarian athletes, L-carnitine supplementation is highly recommended.

10. L-carnitine is safe. Unlike many supplements, the safety of L-carnitine is unquestionable. However, retailers should be aware that carnitine can exist as D- or L-carnitine. Only L-carnitine is safe and natural; D-carnitine is harmful and has been banned by the Food and Drug Administration (FDA) since 1983. However, depending on the process used to manufacture L-carnitine, traces of D-carnitine may still be found in products labeled as L-carnitine. Lonza Group is the only manufacturer of L-carnitine that can guarantee 100% pure L-carnitine and the absence of D-Carnitine, hence the brand name and mark of quality assurance L-CARNIPURE^®. Retailers are advised to contact suppliers of their L-carnitine products to ensure that these products are free from traces of harmful D-Carnitine.

Paula Gaynor, Ph.D., is the Manager of Scientific Affairs and Market Development at Lonza Group. She received her B.Sc. in nutrition and Ph.D. in food science from University College Cork, Ireland. To receive a copy of the mentioned scientific studies, contact Gaynor at pgaynor@lonza-us.com.

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