| EricT |
Experience: 7-10 Years
Join Date: Jul 2005
BCAA, as 0311 mentioned, may have some benefits but just in the realm of a good pre-workout concoction there has been shown no benefits over a fast acting protein and/or carb mixture. Gastric emptying and not "digestion" per se is really the pertinent issue. Absorption in the gut has to do with the amino acid profile of the meal and not wheter it is free form or in the form of di-peptides. I will say that there is plenty of evidence that the absorption of free form amiono acid mixtures is limited by the availibility of transporters and the fact that certain amino acids compete for absorption in the gut. This is probably not the case with leucine per se. But if you were to compare the uptake of leucine with glycine, for istance, you'd see leucine winning the race but being affected by the other amino. If you introduce it in the form of a leucine-glycine peptide you'll get much, much better absorption of both. The idea that free form amino acids absorb better is just completely wrong. If you take a whey isolate 15 to 20 minutes prior to your workout in a fairly dilute solution. Not too much, mind you, say 15 to 20 grams, provided you workout is about an hour, those amino's will be becoming available just in the nick of time. The BCAA profile of whey is very high, so why JUST use BCAA's and not take advantage of having a complete amino acid profile leaking into the bloodstream to be available for that period of increase protein synthesis? I do think that BCAA's are great pre-workout but not superior to whey in terms of supplying amino's. I've noticed an anti-fatigue benefit. A feeling of being able to do more work. But I'd like to caution everyone not to confuse a "feeling" and the subjective experience of doing more with some chemical process that results in more muscle. Leucine affects brain chemicals after all and it may hold of CNS fatigue by reducing trytophan. BUT, you need a lot of protein to build muscle, period. For pre-workout I have a meal an hour or a little more before plus a pre-workout shake consising of whey isolate and carbs. Sometimes I use bcaa's and citrulline malate in addition to this.
there is significant evidence indicating various benefits of BCAA ingestion for athletes. However, the pertitent issue then becomes whether or not BCAA supplements have any advantage over ingestion of protein and/or carbohydrates, which are both significantly less expensive.
The first issue is whether or not BCAA's are superior to protein in stimulating protein synthesis. One study indicates that there is a decline in plasma leucine over five weeks of training in speed and strength athletes consuming 1.26 g protein per kg bodyweight daily, and that leucine supplementation prevents this decrease . However, this study is only confirming a well known fact, which is that strength athletes need high amounts of dietary protein. Studies indicate that in bodybuilders and strength trainers, the amount of dietary protein needed to maximally stimulate protein synthesis is in the realm of 1.4-1.8 g/kg bodyweight (about .6-.7 g/lb), and also that most of these athletes consume well above this amount . For example, a study in stength athletes compared daily dietary protein intakes of .86 g/kg, 1.40 g/kg, and 2.40 g/kg, and found that whole body protein synthesis was increased in the 1.40 g/kg group compared to the lower group, but not further increased in the 2.40 g/kg group. However, rates of leucine oxidation were much higher in the high protein group . This means that if protein intake is adequate, it is doubtful that BCAA supplementation could further stimulate protein synthesis, as the extra amino acids will just be readily catabolized.
Perhaps even more enlightening is the work of Tipton et al., who conducted studies on the types and quantities of amino acids that increase protein synthesis in humans during and after exercise . They compared 40 grams of mixed amino acids to 40 grams of essential amino acids (containing a much higher quantity of BCAA's) to compare their effectiveness in stimulating protein synthesis postexercise, and the two supplements provided a equivalent increases in protein synthesis. The authors then concluded that "there is a maximum rate of net synthesis attainable during hyperaminoacidemia after exercise," and that 40 grams of mixed amino acids is enough to maximally stimulate protein synthesis postexercise.
Another issue is that BCAA supplements are in the form of free-form amino acids, as opposed to a whole protein source. Supplement companies often claim that free-form amino acids are absorbed in greater quantity, more effectively, and more quickly, but this is contrary to the scientific evidence. In general, studies indicate that protein hydrolysates are utilized most effectively, followed by whole proteins, followed by free form amino acids. Intestinal transporters exist for both peptides and free amino acids, and peptides are absorbed more rapidly . Peptides that are not absorbed via a transporter can be rapidly broken down enzymatically. Although not the best model for human athletes, studies in food-deprived rats being refed consistently find that whey protein hydrolysate leads to much higher degrees of weight gain and nitrogen retention than free form amino acids, with one study indicating that whole protein is in the middle in terms of effectiveness [35-36]. Comparative studies have also been done in humans. In healthy subjects, whole protein, protein hydrolysate, and free amino acids all resulted in similar nitrogen balance . Another study in healthy humans found that a protein hydrolysate was absorbed equally as rapidly as free form aminos . Ideally, a study more specific to the conditions in question would be available, but this research indicates that fast-digesting proteins could be just as or more effective than free form amino acids for use before or during exercise.
Carbohydrates may also provide many of the benefits of BCAA supplementation at a much lower cost. As mentioned above, two studies found that BCAA's and carbohydrates together did not provide a performance advantage over carbohydrates alone. Carbohydrates will obviously have glycogen sparing and glucose increasing properties as BCAA's do. Also, carbohydrate supplementation prevents the increase in tryptophan levels caused by exercise, although they may not be as effective as BCAA's . Finally, carbohydrates also have glutamine-sparing and positive immune effects in athletes .
All in all, it would appear that the positive effects of BCAA's on protein synthesis can be achieved by a high protein diet and use of a fast-acting protein prior to and after exercise, and that most of the other possible benefits on exercise performance could be achieved equally as effectively by ingesting simple carbohydrates prior to exercise. If caloric intake must be limited at all costs, or if protein intake is inadequate, BCAA's may be useful in this respect. Also, a unique benefit of reduced CNS fatigue by decreasing tryptophan buildup cannot yet be discounted. – David Tolson
My argument here, btw, is not whether BCAA's work or that supplementation has benefit. ONLY whether supplementing them exclusively pre-workout has benefits over whole proteins, carbs or, ideally, both. It is a cost benefit analysis.
On one hand, you have a bcaa sup that cost more and may provide some benefit in terms of proteins synthese but since you should already be on a high protein diet it's limited and any extra will just be oxidized anyway. On the other hand you have a simple whey isolate or maybe even hydrosolate if your fancy. Which works just as well and has the benefit of giving you MORE of what bodybuilder's need....protein and it's much cheaper.
Last edited by EricT; 11-14-2006 at 10:10 AM..