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New research bulks up sports nutrition

Creatine exploded into the sports-nutrition world years ago and is still the top innovative supplement to hit this industry. No other product introduced in research or the marketplace has come close to touching the status of creatine. However, sports scientists have uncovered the potential of several other supplements, such as beta-alanine, essential amino acids and branched-chain amino acids, as well as the beneficial effects of nutrient intake timing. The differences among various types of proteins and their unique roles in muscle building have also been better elucidated in recent years. As research unfolds, the market quickly adapts by releasing new products.

What's selling now? The combined sports-nutrition and weight-loss industry amassed $16.8 billion in sales in 2005. Sports and energy beverages led the way, with an increase of 27 percent over the previous year, to a total of $7.1 billion in sales. Sports supplements also increased by 6 percent, for a total of more than $2.2 billion in sales.1 On the sports-beverage front, Gatorade still leads the pack with more than 80 percent of the market share, though the remainder of this category takes a step away from the traditional glucose?electrolyte replacement beverage to sports beverages with protein. Given consumer interest in sports beverages and supplements and the latest research in these areas, future introductions in these categories are sure to be forthcoming.

Research on beta-alanine, an intra?cellular buffer, is picking up steam. Beta-alanine plays a role in the body's production of carnosine, a naturally occurring dipeptide (combination of amino acids) that is found in high concentrations in muscle and brain tissues. Beta-alanine works largely as a buffer to offset acid production in the muscle. Delaying acid production may delay muscle fatigue and speed recovery.

In one study, 13 male subjects with an average age of 25.4 years supplemented with 4 g to 6 g of beta-alanine every day for 10 weeks. They showed average increases in muscle carnosine of 58.8 percent and 80 percent after four and 10 weeks, respectively. They then completed an exhaustive cycling test at 110 percent of maximum power. The men showed a 13 percent increase in total work after four weeks of supplementation and a further increase of 3.2 percent after 10 weeks, with no changes in the placebo group.2

Two recent studies examined the effects of a combination of beta-alanine and creatine on various aspects of athletic performance. In a double-blind, placebo-controlled, randomized study, researchers assigned 55 males (average age of 24.5 ? 5.3 years) to one of four groups for four weeks of treatment: placebo, 5.25 g/day creatine, 1.6 g/day beta-alanine or 1.6 grams/day beta-alanine plus 5.25 g/day creatine. The participants then completed exhaustion tests on a cycle ergometer. No between-group differences were noted from pre- to post-test. The group that took beta-alanine plus creatine demonstrated significant improvement from pre- to post-test in five of eight measurements of cardio-respiratory endurance. More specifically, this group improved maximal oxygen uptake and power output at metabolic thresholds, as well as the percentage of maximal oxygen consumption, which was maintained at ventilation threshold (the point at which ventilation deviates from a steady linear increase and instead increases exponentially). The creatine-only group showed pre- to post-test improvement in total time to exhaustion and power output at ventilation threshold. The beta-alanine-only group showed an increase in power output at metabolic thresholds from pre- to post-test. The results of this study suggest that supplementation with creatine plus beta-alanine may enhance submaximal endurance performance.3

In a second study, 33 male college football players were randomized into one of three groups over the course of a 10-week resistance-training program: 3.2 g/day beta-alanine plus 10.5 g/day creatine, 10.5 g/day creatine or placebo (10.5 g/day dextrose). Significantly greater improvements in strength, muscle mass and percent body fat were noted in the beta-alanine plus creatine group, compared with both the creatine-only and placebo groups.4 While intense training increases muscle levels of creatine and carnosine, supplementation even over brief periods can raise the levels even higher. Therefore, loading with 4 g to 6 g/day of beta-alanine may lead to prolonged exercise bouts by delaying acid production. This, in turn, might enable athletes to recover from strenuous training more rapidly. Additionally, the combination of beta-alanine plus creatine may increase strength and muscle mass more than creatine alone.

EAA and protein intake timing
Though it is clear that essential amino acids are necessary for stimulating muscle protein synthesis, the exact dosage per kilogram of body weight for maximal MPS remains unknown. EAA studies indicate that there is a dose-response relationship to EAA consumption and MPS, though as little as 6 g EAA will effectively stimulate MPS.5 The EAAs include valine, leucine, isoleucine, lysine, methionine, phenylalanine, threonine and tryptophan. (Histidine is also considered essential in children). Nonessential amino acids do not affect MPS.5,6

Previous research in this area empha?sized the importance of taking EAA with a simple carbohydrate (sucrose) about 30 minutes before resistance training, and that this may be more important for stimulating MPS than taking EAA post-exercise.7 Though their research indicates the timing of EAA intake may be very important in stimulating MPS, the authors of a recent study concluded that the timing of protein ingestion—pre- or post-exercise—may not be as significant.

Seventeen healthy subjects took 20 g of whey protein (corresponding to approximately 9 g EAA) pre- or post-exercise (10 sets of eight repetitions of a leg extension). Amino acid uptake was not significantly different pre- vs. post-exercise.8 In addition, when results of this study were compared with those of an earlier study by the same researchers, the increase in arterial amino acid concentrations during exercise was approximately 100 percent for EAA,7 but only about 30 percent for whey proteins ingested prior to exercise. This comparison indicates that amino acid delivery during exercise is greater with ingestion of EAA than intact whey protein prior to exercise.8 Greater EAA delivery is the goal—a higher amino acid concentration in skeletal muscle increases muscle protein synthesis.9

For years, sports beverages were composed mainly of glucose, electrolytes and water. However, recent research lends support for newer carbohydrate-protein beverages on the market. One of the first of these studies showed that when consumed every 15 minutes during aerobic exercise and immediately after, a carbohydrate-protein beverage may improve time to fatigue and attenuate muscle damage, compared with a beverage containing only carbohydrates. However, total carbohydrate content was the same per kilogram of body weight, and therefore the carbohydrate-protein beverage provided 20 percent more calories. Therefore, the greater caloric content may have played a role as well.10

A more recent study required young, healthy males to complete an exercise-exhaustion trial at 70 percent VO2 peak (highest oxygen uptake measured) on a cycle ergometer, followed by a time-to-exhaustion trial at a standard workload (80 percent VO2 peak) 24 hours later. Subjects consumed either a carbohydrate-protein-antioxidant beverage or an isocaloric carbohydrate-only beverage every 15 minutes during exercise and immediately afterward. Subjects who consumed the CHOPA beverage in the first trial consumed CHO in the second, and vice versa. Though there was no between-group difference in time to fatigue or total performance time in either trial, post-exercise creatine kinase levels and lactate dehydrogenase (two measures of muscle damage) increased significantly from baseline levels in the CHO trial but not in the CHOPA trial. In addition, median post-exercise soreness was higher in the CHO trial. Though this study indicates there may not be a performance advantage, CHOPA beverages, when consumed during an endurance bout and immediately afterwards, may attenuate post-exercise muscle damage.11

The marketing lingo on arginine supple?ments often suggests that it can promote lean tissue gains. However, recent research does not support this claim. In a randomized, double-blind, placebo-controlled experi???ment, 35 resistance-trained men were supplemented with 12 g/day of L-arginine alpha-ketoglutarate or placebo for eight weeks, during which they participated in four days a week of periodized resistance training (a systematic method of alter?nating high training loads with decreased loads to improve components of muscular fitness). Significant differences were noted in measurements including one-repetition maximum bench press, Wingate peak power, blood glucose and blood arginine at eight weeks.12 A 12 g/day dosage of AAKG is approximately 10 times as much as most supplements deliver per serving. Other recent arginine research indicates that a 7 g/day dosage combined with resistance exercise does not significantly stimulate growth-hormone response compared with exercise alone.13

Carnitine research breakthrough
L-carnitine was popularized in the 1980s as a fat-burning supplement. The premise behind this concept is sound; carnitine is a "carrier" that transports fatty acids across the mitochondrial membrane for beta-oxidation to occur. In essence, carnitine plays an essential role in fat oxidation.14 However, previous research indicates that supplemental L-carnitine does not increase skeletal muscle carnitine content, making it all but useless in terms of direct enhancement of endurance or fat loss.15,16,17

Recently, scientists discovered a way to make carnitine supplementation more effect?ive. Raising serum insulin levels at the same time carnitine is taken appears to increase muscle carnitine content. In a British study from the University of Nottingham, researchers used infused insulin at a steady rate for six hours in seven healthy men. One hour after the start of the insulin infusion, subjects were infused with 60 mmol/L-carnitine or an equivalent volume of placebo (saline) over the remain?ing five hours of the insulin infusion period. Total carnitine content in skeletal muscle increased significantly by 15 percent in subjects infused with carnitine, while those infused with saline exper?ienced no change. In addition, muscle glycogen content increased significantly in both groups during the insulin infusion; 24 hours post-study, muscle glycogen content increased again, above study values in the carnitine-supplemented group. Muscle pyruvate dehydro?genase complex activity, which plays an important role in fatty acid synthesis and whole-body carbo?hydrate regulation, was decreased by 30 percent in the carnitine group. These results suggest that the increase in muscle carnitine content led to decreases in carbo?hydrate oxidation, increased glycogen storage and increased fatty acid oxidation.18 Earlier research also supports the notion that increased insulin levels support muscle carnitine content during carnitine supplementation.17

The same group of researchers examined a more practical way to raise insulin levels—by ingesting simple carbohydrates. In this study, 94 g of glucose (in a beverage) was used to facilitate increases in insulin during carnitine supplementation (3 g/day). In comparison with placebo plus 3 g/day carnitine, the carbohydrate group showed a significant decrease in urinary carnitine excretion, indicating increased carnitine retention associated with concurrent carbohydrate intake.17

We know that carbohydrates vary tremendously in their ability to help us rapidly synthesize glycogen post-exercise. The recommendation has always been to ingest simple sugars that rapidly spike insulin levels, thereby replenishing glycogen stores quickly as well. However, even simple carbohydrates differ; higher molecular?-weight carbohydrates are superior in their ability to help stimulate glycogen synthesis.19

Marie Spano, M.S., R.D., is a freelance writer, spokeswoman and vice president of the International Society of Sports Nutrition.

1. [No authors listed] Sports nutrition and weight loss markets VI. Nutrition Business Journal 2006; 11(9).
2. Hill CA, et al. Influence of ?beta-alanine supplementation on skeletal muscle carnosine concentrations and high intensity cycling capacity. Amino Acids 2007;32(2):225?33.
3. Zoeller RF, et al. Effects of 28 days of beta-alanine and creatine monohydrate supplementation on aerobic power, ventilatory and lactate thresholds, and time to exhaustion. Amino Acids Sept 5, 2006. [Epub ahead of print]
4. Hoffman J, et al. Effect of creatine and beta-alanine supplementation on performance and endocrine responses in strength/power athletes. Int J Sport Nutr Exerc Metab 2006 Aug;16(4):430?46.
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10. Saunders MJ, et al. Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage. Med Sci Sports Exerc 2004;36(7):1233?8.
11. Romano-Ely BC, et al. Effect of an isocaloric carbohydrate-protein-antioxidant drink on cycling performance. Med Sci Sports Exerc 2006;38(9):1608-16.
12.Campbell B, et al. Pharmacokinetics, safety, and effects on exercise performance of l-arginine aalpha-ketoglutarate in trained adult men. Nutrition 2006;22:872?81.
13. Collier SR, et al. Oral arginine attenuates the growth hormone response to resistance exercise. J Appl Physiol 2006;101:848?52.
14. Champe PC, Harvey RA. Metabolism of dietary lipids. In: Biochemistry, 2nd edition. J.B. Lippincott Co. Philadelphia: 1994. pp 181?2.
15. Brass EP. Supplemental carnitine and exercise. Am J Clin Nutr 2000; 72:618S?23.
16. Wächter S, et al. Long-term administration of L-carnitine to humans: effects on skeletal muscle carnitine content and physical performance. Clin Chim Acta 2002;318:51?61.
17. Stephens FB, et al. Insulin stimulates L-carnitine accumulation in human skeletal muscle. FASEB J 2006;20:377?9.
18. Stephens FB, et al. An acute increase in skeletal muscle carnitine content alters fuel metabolism in resting human skeletal muscle. J Clin Endocrin Metab 2007;91(12):5013?8.
19. Piehl Aulin K, et al. Muscle glycogen resynthesis rate in humans after supplementation of drinks containing carbohydrates with low and high molecular masses. Eur J Appl Physiol 2000;81:346?51.

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