Sports Nutrition

Chapter 59 Sports Nutrition




Becoming leaner, faster, stronger, and performing better for longer all while staying healthy is the hope of every athlete from the weekend warrior to the elite professional. Sports nutrition is about fueling performance, recovering from stress, building skills quickly, and maintaining optimal body composition for the sport. In this chapter we will cover the pertinent issues around sports nutrition, including supplementation for performance, fitness, and fat loss.



image Nutrition and Performance



Performance Nutrition and Fat Loss


Before we begin the discussion of sports nutrition, it is useful to cover the topic of body composition. Excelling and participating in sports has much to do with achieving and maintaining an ideal body composition. Athletes seek to optimize the correct ratio of muscle tissue to fat weight that allows the best performance advantage in their sport. More times than not, simply participating in the sport improves body composition. However, when it does not, an athlete may, at times, seek to increase muscle mass or decrease their fat weight. In addition, the average recreational sport enthusiast, who is not engaged in the competitive side of athletics, will often adopt the eating habits of the elite athletes in the sport they participate in. This can be a point of confusion.


The “glycogen paradigm” is a way of thinking about sports performance that seeks to maximize muscle sugar storage. This, it is believed, is the best way to increase training intensity, accelerate recovery, and improve performance. This glycogen dogma has resulted in confusion for athletes and exercise enthusiasts regarding optimal exercise for improving body composition. It has been known for some time that maximizing glycogen storage increases the performance of endurance athletes. In a 1991 study, Wagenmakers et al1 showed this effect conclusively. However, this study also showed a direct negative association between glycogen storage and fat burning. Other studies have shown that exercise done in a glycogen-depleted state may have benefits for increasing fat loss.24


This information has consequences for athletes and weekend warriors. At times, fat loss is the key aim of an athlete. When this becomes the case, it may be important to tweak the glycogen-centered philosophy of maximizing performance to an approach that instead focuses on fat loss. Health practitioners working with athletes and the general population would be wise to remember the positive association of glycogen with performance and the negative association with fat loss.



Diet Concerns for Athletes


Nutrition for exercise performance involves fueling the body for performance. This requires optimal energy resources to make up for caloric expenditure during exercise. Athletic activities can use significant resources. High intensity daily exercise can burn from 600 to 1200 calories/day.58 Elite athletes, such as professional cyclists, can burn as high as 12,000 calories/day, necessitating a large compensatory calorie intake. Caloric needs this high can be extremely difficult to obtain through food.512 This makes supplementation necessary for athletes undergoing heavy training.


Health care providers advising athletes on nutrition must take many things into account. In addition to the caloric issues just described there are several other issues. Many athletes undergoing the intense stress of training can experience loss of appetite especially after intense exercise.13 Athletes are often also under the constraints of tight schedules of competition and travel requirements that can interrupt scheduled meals. Given the already tight training schedules, athletes can quickly become overwhelmed by considerations of food.


To account for these issues, athletes engaged in heavy training should work to assure muscle is not lost and weight is maintained. This means eating calorie dense meals and snacks that are convenient for an athlete’s lifestyle. Although real and whole foods should be emphasized, the use of protein bars, meal replacement shakes, electrolyte beverages, and nutritional vitamin and mineral supplements will often be needed. Athletes should eat between four and six meals per day and should eat in consistently timed intervals. Meal and snack timing around training is also an important consideration to replenish energy and aid recovery.13 It is important to understand that without calorie balance many supportive training aids will not provide much advantage.



Macronutrient Ratios


In addition to the caloric considerations of athletes, balancing the protein, fat, and carbohydrate ratio is also important. Recreationally active individuals are usually advised to consume from 45% to 55% carbohydrates, 10% to 15% protein, and 25% to 35% fat.58 The macronutrient needs of athletes can far exceed these numbers. Carbohydrate requirements for athletes can increase up to 10% to replenish and maximize liver and muscle glycogen storage.7,8 These carbohydrates should come from low glycemic index sources that do not cause rapid fluctuations in blood glucose. Because higher levels of carbohydrate can be hard to consume, fruit juices, energy bars, and other convenience foods may be considered.


Research related to carbohydrate intake in athletes shows there might be what we call a “carbohydrate tipping point.”7 This is a level of carbohydrate beyond which there ceases to be a performance advantage. Research suggests the body can burn 1 to 1.1 g of carbohydrate per minute, amounting to roughly 60 g of carbohydrate per hour of exercise.7 Harger-Domitrovich et al14 showed approximately 50 g of carbohydrate for a 165 lb individual was the optimal intake of carbohydrates for athletes. This amounts to 0.27 g of carbohydrate needed per pound of body weight each hour during exercise.


It is also interesting to note that not all carbohydrates are created equal. Research suggests that sugars composed mainly of glucose (maltose, maltodextrin, and other polysaccharides) are burned at a higher rate compared with nonglucose sugar (fructose, galactose, etc.). The combinations of these sugars seem to be most advantageous.7 Evaluating carbohydrate sources on the relative ratios of these sugars may be wise. The glucose/fructose ratio of close to 1:1 seems optimal.



Protein


Protein makes up about half the human body’s dry weight and is the second most abundant compound in the body after water. Recent research on protein intake has shown that athletes require two times or more of the reference daily intake.7,1520 It is now recommended that athletes involved in very high volume training consume between 0.7 and 0.9 g of protein per pound of body weight per day. This amounts to between 115 and 150 g of protein per day for a 165 lb athlete. This would be the equivalent of about five to seven 3 oz servings of chicken, fish, or other lean protein per day. Protein considerations are especially important for endurance athletes who are more susceptible to protein malnutrition due to the catabolic hormonal environment created by their sport.2022


Not all protein is the same. The amino acid content of protein sources can vary and has direct bearing on quality. Different types of protein can be described as fast proteins or slow proteins.23, 24 Slow proteins are digested more evenly and take longer to process. Fast proteins are digested more rapidly and allow amino acids to be quickly available to the body. The typical fast and slow protein sources are whey and casein, respectively. Health care providers working with athletes may want to look at slow proteins as good meal options, whereas fast protein may be great options to aid performance and recovery by timing them for intake before and after exercise. The best sources of protein are low fat and have a high biological value with optimal amino acid ratios. These sources include skinless chicken, lean beef, fish, egg whites, skim milk, lean pork, and the supplemental milk proteins casein and whey.


The International Society of Sports Nutrition published its position stand on protein intake in 2007, highlighting the following points25: (1) highly active individuals should consume between 1.4 and 2 g of protein per kilogram of body weight; (2) concern that protein intake within this range is unhealthy is unfounded; (3) attempts should be made to get protein from whole foods, but supplemental protein is a safe and viable method of protein intake; (4) timing protein intake before and after exercise may have benefits, including enhanced recovery and development of muscle mass; and (5) certain proteins, such as branched chain amino acids (BCAAs) have been shown to be beneficial for increasing the rate of protein synthesis, decreasing protein breakdown, and increasing recovery from exercise.6 Exercising individuals require more protein than their sedentary counterparts.



Fat


Fat intake for athletes has several important considerations and depends on the athlete’s goals and training state. In general, athletes’ fat recommendations should be at or slightly greater than their nonathlete sedentary counterparts.7 High volume athletic training has been shown to lower testosterone concentrations, and decreasing fat intake can exacerbate this effect.2628 Most research suggests athletes should keep their dietary fat intake at around 30% of total calories. However, ultra-endurance athletes, in particular, may go much higher than this. Athletes undergoing very intense training regimes have been shown to safely tolerate and benefit from diets containing as much as 50% of total calories from fat.29 As mentioned previously, weight loss is occasionally a concern for athletes. In these cases, a lower fat diet may be advisable, with research suggesting a diet of 0.25 to 0.5 g of fat per pound per day.30 Fat quality is also a concern. The polyunsaturated fatty acid ratio of ω-6/ω-3 may be a concern in immune system function and inflammatory responses. Saturated fat intake may also be associated with more optimal testosterone responses.28 Given these considerations of fat and the emerging understanding of the different function of fats, it is wise for athletes to consume a wide range of dietary fats, with a special eye towards balancing the ω-3/ω-6 ratio.



Performance, Recovery, and Nutrient Timing


Athletes and those working with them can benefit greatly from understanding how to time meals for performance and recovery. When it comes to performance nutrition, it is useful to think about first maximizing storage capacity (i.e., filling the liver and muscle glycogen stores) and fueling exercise (i.e., having nutrients more recently consumed to fuel exercise).58 Complex carbohydrates take about 4 to 6 hours to be digested, absorbed, and then stored in the liver and muscle as glycogen.5831 Recommendations regarding carbohydrate loading for training and competition should take this into account. Morning training sessions or competition will benefit from nighttime loading strategies, whereas afternoon competition and training sessions will benefit from morning loading strategies. A light carbohydrate and protein shake roughly 45 minutes (30 to 60 minutes) before activity has been shown to improve performance toward the end of high intensity activity. The inclusion of protein also serves to spare muscle tissue by decreasing the need for the body to cannibalize its own muscle tissue.32,166


Although exercise sessions less than an hour require no special nutritional or hydration strategies, exercise sessions lasting longer do. Strategies that manage pre-, post-, and within workout nutritional requirements can dramatically aid performance and recovery. This is where electrolyte solutions and sports drinks consumed before and during exercise have an important role to play. These beverages can help prevent low blood sugar, optimize hydration, replace lost minerals, and reduce the immune suppression that occurs after intense long duration exercise.33,34 A carbohydrate beverage of 6% to 8% with an equal mixture of glucose and fructose taken every 20 minutes during exercise is advised.7,35,36 In addition, adding protein to carbohydrate intake may result in higher rates of glycogen storage after exercise.13,33,36,37 Research suggests consumption of approximately 20 g of a rich source of essential amino acids (e.g., whey protein) combined with 40 g of a good glucose source (e.g., grape juice) taken 40 minutes before exercise may be useful and within 3 hours after exercise may improve performance and aid recovery. The addition of a small amount of fat may also be helpful in stabilizing blood glucose levels.36


After exercise there is a unique opportunity to fuel the body for recovery. During this “recovery phase” nutritional strategies should be instituted as soon as possible, and at least within the first 30 minutes after the cessation of exercise. A mixed carbohydrate protein beverage containing close to a 3:1 ratio of carbohydrate/protein within 3 hours after exercise appears to provide greater recovery benefits than lesser amounts of carbohydrate.13,33,36,37,38 Upon completion of this post-workout “snack,” another more carbohydrate heavy post-workout meal should be eaten again within 90 minutes.


Most athletes will taper their training by one third to one half 2 to 5 days before their event. During this time, it may be beneficial to consume 200 to 300 extra grams of carbohydrate daily. This technique has been shown to maximize glycogen storage before the event and improve performance.36



Water


Easily the most beneficial ergogenic aid is water. Working to prevent dehydration during exercise is one of the most useful endeavors for improving exercise performance. Intense exercise can result in significant loss of water through sweat. When this fluid is not replaced, athletic performance will suffer. A loss of 2% water through sweat can impair the ability to compete and a loss of 4% can result in the inability of the body to cool itself during exercise.39 Athletes can lose 1 to 2 L in sweat through exercise per hour. Unfortunately, athletes cannot rely on thirst perception to regulate fluid balance.39 There are several objective ways for athletes to measure fluid loss.39 One way to ensure adequate hydration recovery is for athletes to weigh themselves before and after exercise and drink 3 cups of liquids per pound of weight lost through exercise. During heavy exercise athletes should consume 1 to 2 L of water or glucose and/or electrolyte beverage per hour.39,40



Vitamins and Minerals


It is now recommended by most medical organizations that a low-dose multivitamin be consumed daily to assure optimal vitamin status.7,41 Few, if any, vitamins and minerals have been shown conclusively in research to have any performance benefit. However, the nutritional status of an athlete can impact quality of performance, training, and recovery.7,4144 When considering vitamin and mineral supplementation for athletes, health care practitioners should view their recommendations in the context of nutrient adequacy. Athletes may be more susceptible to vitamin and mineral inadequacies given the previously mentioned issues on nutrition and potential caloric deficits. Although there may be no direct benefits to performance, many vitamins and minerals aid recovery and support.7,4144


Vitamin C and zinc in particular have good research suggesting immune enhancement during intense training periods.7 Vitamin C and E, along with other antioxidant nutrients, may also protect athletes from excessive oxidative damage, which could also lead to immune suppression.7


Mineral deficiencies are particularly problematic for athletes. Restoring any mineral deficiencies can aid performance.7 Certain minerals may also provide benefit for optimizing performance. Calcium is one mineral that can aid athletes. Although there is no evidence that calcium supplementation improves performance, at supplement levels of approximately 1000 mg/day it has been shown to assist athletes susceptible to osteoporosis as well as improve body composition.45,46 Phosphorus supplementation may have ergogenic effects when supplemented as sodium phosphate, but not other forms (calcium phosphate, potassium phosphate, etc.).47 Levels of supplementation for phosphate are 4000 mg/day (1 gram tribasic dodecahydrate sodium phosphate 4 times/day) for 3 days for endurance improvement. Sodium intake has benefit for training in the heat and reduces the risk of hyponatremia.48 With most minerals as with vitamins, the real benefit to athletes comes when identified deficiencies are corrected. Restoring vitamin and mineral status to optimal levels can aid exercise performance.7,4144


Along these lines, vitamin D is a special consideration. Vitamin D deficiency is now epidemic, and athletes have the same rates of deficiency as the rest of the public.49, 50 In one study of elite female gymnasts, 77% were found to have vitamin D levels lower than 35 ng/mL and a full third had levels lower than 10 ng/mL.50 In a group of athletes susceptible to prolonged and constant bone stress (i.e., long distance runners), this finding was especially troubling and underscores the need for athletes to ensure adequate vitamin D status.


Although vitamin D supplementation in those with sufficient vitamin D does not appear to increase performance, vitamin D therapy delivered to deficient athletes may improve performance.51, 52, 53 Vitamin D is known for its role in bone metabolism. The fact that skeletal muscle has vitamin D receptors is not commonly known. As far back as the 1930s, there have been numerous reports of the beneficial effects of ultra-violet therapy on athletic performance.53,54 There are also studies that suggest the season of training makes a difference. One of these studies showed that training in the summer months creates greater gains than the same volume of training in autumn or winter despite the same stimulus.54


In both older and younger individuals, adequate vitamin D status impacts neuromuscular function and may have a specific relationship to the maintenance of the fast twitch type 2 muscle fibers.49,51,53,55,56 In a study on teenage athletes, vitamin D deficiency lowered muscle power and force.57 Vitamin D levels are also related to myalgia, fatigue, and reduced motivation to exercise. Studies in older adults showed that levels of vitamin D were correlated with the propensity to fall.58 A meta-analysis on vitamin D levels showed a 20% reduction in the risk of falling in those with higher levels.59 This was likely due to vitamin D’s ability to improve reaction speed, balance, and neuromuscular performance. Much of this may be explained by the ability of vitamin D to help maintain and even build type 2 muscle fibers.


Athletes should be tested for vitamin D levels with a serum 25-hydroxy vitamin D laboratory test with a target between 50 and 100 ng/mL. If they are found to be insufficient, a combination of supplementation and sun exposure is advisable. For quick restoration of adequate vitamin D levels, 50,000 IUs of vitamin D per week for 12 weeks has been shown to allay symptoms of vitamin D deficiency. Maintenance doses of between 1000 and 10,000 IU/day, depending on sun exposure and living latitude, should also be considered to prevent deficiencies.



image Assessment



Laboratory Evaluations for Sports Nutrition


Nutrient deficiencies can impact many aspects of physical performance, recovery, and immune function. Athletes, because of the imposed increases in metabolism, can be at an increased risk for nutrient deficiencies. Serum testing is a reliable and useful tool for diagnosis of severe nutrient deficiencies, but may be inadequate for certain vitamins and minerals.60 Therefore, it is useful for those working with athletes to have more functional tools for assessment of metabolic and nutritional needs.


Testing blood for nutritional levels can be misleading. Serum nutrient concentrations are closely regulated by the body and can fluctuate based on recent intake. Furthermore, some vitamins and minerals are almost entirely found intracellularly. As stated by Lord and Bralley in their textbook Laboratory Evaluations for Integrative and Functional Medicine, “for various reasons specific to each vitamin, it is possible for an individual to have normal serum levels of a vitamin while exhibiting signs of insufficiency for that vitamin owing to a lack of adequate intracellular concentration to meet the metabolic demands of the cells.”60 Given these factors, serum may not always be the best means of determining nutritional status for all nutrients. There are now a range of laboratory analyses that can give more functional assessments of nutrition status.60 The ones that may be most beneficial are adrenal hormone profiles (cortisol and dehydroepiandrosterone [DHEA]), organic acid testing, and intracellular nutrient analysis.



Adrenal Hormone Testing


Analyzing the adrenal hormones cortisol and DHEA can give insight into training status and whether an athlete may be overtraining or overreaching.6163 Cortisol and DHEA provide a good indication of catabolic versus anabolic balance in the body as well as neuroendocrine adaptation to stress. The test is simple and noninvasive, involving salivary collection at four time points during the day (morning, noon, evening, and night). Depending on the laboratory, the cortisol and DHEA test may also provide markers of immune function, such as immunoglobulin-A. All these measures are important for athletes looking to compete at high levels for prolonged periods.


The body goes through four stages in response to stress. Stage 1 occurs in response to acute stress and involves elevations in cortisol with no changes in DHEA. Stage 2 involves continued stress and is marked by a sustained cortisol peak with a matching elevation of DHEA. At stage 3, when stress continues and becomes chronic, cortisol levels drop, whereas DHEA stays high. Finally, both cortisol and DHEA fall, a stage often referred to as adrenal exhaustion or stage 4.


Testing athletes for levels of adrenal hormones gives important guidance concerning nutritional therapy and supplementation. Cortisol is a highly catabolic agent, and increased cortisol levels with normal to low DHEA indicate excessive stress and potential muscle wasting.60 This necessitates increased protein intake, especially increased glutamine.64 High cortisol levels also give an indication of increased need for other nutrients that are easily depleted through increased metabolic activity (e.g., magnesium, zinc, and vitamin B6).60 Cortisol suppressing supplements, such as phosphatidyl serine, may also be indicated,65 as is the potential for DHEA supplementation and/or immune support.66 Changes in adrenal hormones may occur long before seeing clinical symptoms and can be used to monitor training status and recovery.



Organic Acid Testing


Organic acid testing is a useful analysis that looks at metabolic by-products in urine.60 The test does not measure actual vitamins and minerals but assesses them indirectly by measuring excreted metabolic by-products. Although the test is not diagnostic, it can be used to analyze the metabolic consequences of insufficient nutrient intake. It can also give insight into toxic exposures, amino acid need, and neuroendocrine function.


Fats, proteins, and carbohydrates become carboxylic acids before they are completely burned to carbon dioxide. These acids, formed by the body’s metabolic processes, are usually low or nonexistent in urine. When perturbations occur in metabolism due to inefficient enzymes as a result of genetic polymorphisms and/or lack of a vitamin or mineral cofactor, the metabolic by-products can build up in the cell, be released into the blood and then begin to show up in the urine. The organic acids that appear can then be traced back to known biochemical pathways, indicating a particular nutrient need.


Given the fact that almost all nutrients become ergogenic when there is a deficiency or increased need, organic acid testing may be useful in understanding what nutrients may be indicated for a particular athlete and if the supplements they are currently taking are actually doing the job. Using organic acid testing may provide health care practitioners working with athletes a way to pinpoint potential nutrient issues and bolster key metabolic pathways.



Intracellular Nutrient Analysis


Because many nutrients, like magnesium, are not well measured in serum, another useful functional analysis for athletes is intracellular nutrient analysis.60 This testing involves drawing blood, and isolating white blood cells and growing them in a nutrient rich medium. Individual nutrient concentrations are then manipulated one by one while measuring cell growth rates. Cellular growth from an athlete with insufficient levels of a nutrient will be slower than from an athlete with sufficient levels.67 This allows tailored nutrient supplementation to optimize intracellular levels of all nutrients.




image Critical Evaluation of Ergogenic Aids


It is important for the health care practitioner to be aware of the large gap that often exists between supplement marketing and research. Given that nutritional supplements are not regulated to the same degree as pharmaceuticals, and little financial incentive exists to research natural compounds, it is important to look for valid and objective resources on nutritional supplements. When evaluating whether a nutraceutical might be useful, it is important to keep several things in mind.7


A good first question to ask is “does the basic science make sense?” Natural health practitioners need to be good students of biochemistry and physiology. Knowing the compound and its involvement in biochemical pathways is a necessary first step. If the mechanism of action “makes sense” from a biochemical perspective, the supplemental aid may have merit. A good example here is the use of the nutrient L-carnitine. Understanding the biochemistry of this nutrient as key in delivering fat to the mitochondria to be burned for energy allows suspicion that it may have fat loss and performance benefits.


The next question is “is it feasible to deliver the nutrient in a form that can actually be absorbed and utilized by the body?” Although a nutrient may seem like a perfect candidate for performance enhancement properties, if it cannot be delivered to the body in a safe, feasible, and usable form, it will not have much use. In the case of L-carnitine, there are several issues that warrant consideration. First, L-carnitine is not well absorbed; therefore, understanding the different delivery forms is essential. Would L-carnitine bound to tartrate, fumarate, or another molecule be most feasible for delivery? Also, in the case of amino acids like carnitine, there are two forms, L-carnitine and D-carnitine. L-carnitine is active in the body, whereas D-carnitine is not and can actually block the action of L-carnitine. Confidence would therefore be less on studies using the racemic mixture of this nutrient versus those using pure L-carnitine.


Another important consideration is “does any good research exist on the substance?” Are the studies in vitro or in vivo studies? Were they animal or human studies? Was the sample size big enough? Was the study designed appropriately? Was it well controlled? Human clinical trials with a large sample size that are double blinded and placebo controlled are obviously the gold standard and should be weighted heavier. However, these types of studies often do not exist for sports performance supplements, accounting for much of the skepticism regarding sports performance aids. Much of this skepticism is warranted, although discounting a supplement purely on the basis of lack of these types of trials is probably not wise.


Some final considerations would be whether or not the product is safe, legal, and appropriate. In 2006, the 109th Congress passed the Dietary Supplement and Nonprescription Drug Consumer Act. This law requires supplement companies to disclose all complaints about their products and make them available to the public. For supplement issues that are more serious in nature, the companies must notify the Food and Drug Administration within a 2-week time frame. There are also consumer bodies that help police the industry. These organizations independently test supplement products against claims of efficacy and issues with contamination and can be useful resources to those advising supplement use. Finally, there are always products that are completely safe that may present issues in certain populations. All these considerations should be evaluated when using nutritional supplementation.



image General Health Concerns for Athletes


The American Medical Association has suggested Americans use supplemental vitamins to maintain health; these recommendations seem especially prudent in the athletic world. Although there is no performance benefit to the use of multiple vitamins and minerals, as discussed previously, athletes can be susceptible to deficiencies and/or require more support in areas due to increased vulnerability of stress or injuries encountered during sports. Glucosamine can aid in the healing of damaged cartilage and lessen joint pain.69 Supplements such as zinc, glutamine, vitamin C, lipoic acid, selenium, and other nutrients may support immune function and antioxidant capacity.57,7072 Amino acids are especially useful. Creatine, whey protein, BCAAs, and L-carnitine tartrate have all been shown to help athletes through the stress of intense training periods.57 Finally, ω-3 fats can help balance inflammatory and anti-inflammatory reactions in the body.



image Nutritional Supplements


Obviously, a full treatment of all the nutraceuticals purported to have beneficial effects in exercise and body composition could fill an entire book. We selected the compounds discussed here that demonstrated the most research supporting their use as ergogenic aids. We attempted to avoid looking at compounds that have strong theoretical support for their use, but have not yet been studied. We gave special consideration to compounds that have been studied in humans and have been evaluated under double-blinded and placebo-controlled conditions. Newer compounds that did not meet these criteria may not be covered. In certain cases, we covered compounds that are novel in their reported use as ergogenic substances.



Arginine


Arginine has several potential benefits for athletes, including increasing human growth hormone production, increasing blood flow, increasing mitochondrial biogenesis, and increasing fat loss and muscle gain. Many of these effects are related to nitric oxide, for which arginine is a precursor. However, several of these benefits are relatively new discoveries regarding arginine supplementation. Animal studies and human studies showed arginine might have particular benefit in improving exercise capacity and body composition.


Arginine may play a role in endurance performance. A 2010 study showed that a proprietary arginine supplement given to elderly male cyclists was able to positively impact performance. The arginine supplement significantly increased the anaerobic threshold within 1 week of beginning supplementation, with the effect lasting throughout the 3-week study.73 There was no change in maximal oxygen consumption (VO2max) in this particular study. However, in another study, this time on younger cyclists, oxygen kinetics were sped up in relation to L-arginine supplementation.74 Another study in 2010 showed arginine’s potential role in illness associated with reduced cardiovascular capacity.75 In this analysis, arginine supplementation improved exercise capacity in heart transplantation patients, resulting in furthering the distance walked and delaying the ventilatory threshold by 1.2 minutes.


In addition to endurance benefits, arginine may also have a role to play in strength training. An April 2010 study showed increased growth hormone and insulin-like growth factor 1 release in response to heavy resistance training.76 This newer study lends credibility to older reports.


Research on rats, pigs, and humans showed arginine to be a potential antiobesity aid through several unique mechanisms.78 Supplemental arginine appears to have activity that increases glucose and long-chain fatty acid oxidation while at the same time suppressing gluconeogenesis and lipogenesis. In rats, L-arginine was shown to increase muscle mass by 12% and increase glucose metabolism by 14% without impacting insulin. Most interestingly, arginine was shown to coax white adipose tissue to become brown adipose tissue and, as a result, significantly elevated the metabolic rate. Arginine appears to act partly via its conversion to nitric oxide. It may act via cyclic guanosine monophosphate and cyclic adenosine monophosphate dependent mechanisms. It was found to increase mitochondrial biogenesis, upregulate GLUT-4 receptors, and improve muscle mass.


A 21-day randomized and double-blind, placebo-controlled study of arginine in obese men was conducted in 2006 by Lucotti et al.79 Thirty-three obese males were put on a low calorie diet (1000 kcal/day) and an exercise program (45 minutes of exercise twice per day for 5 days/week). They were then randomized to receive 8.3 g/day of arginine or placebo. As expected, the lifestyle intervention resulted in weight loss, waist circumference reduction, lowered fasting glucose, and reduced insulin in both groups. However, the arginine group had statistically better responses in most measures compared with the placebo group (P <0.0001). Most interestingly, the arginine group was able to maintain their muscle mass, whereas the placebo group had significant reduction in lean body mass. Forty-three percent of the weight lost in the placebo group was fat compared with a full 100% for the arginine group.


Only gold members can continue reading. Log In or Register to continue

Sep 12, 2016 | Posted by in MANUAL THERAPIST | Comments Off on Sports Nutrition
Premium Wordpress Themes by UFO Themes