And I'm Back with a Head Full of New Knowledge

Summer school ended Wednesday and it appears that I barely passed organic chemistry II. I'm not entirely happy with my grade, but I believe it is enough to allow me to enroll in upper division nutrition courses. I will have to improve my grade for that course at a later date.

Sports nutrition was a different story; I did quite well in the class in spite of my lack of knowledge in the area. Now that I've completed the class, I wish I had this knowledge back when I was playing varsity tennis in high school. I can remember a few matches where a better diet and hydration plan would have helped me play better or helped me recover from fatigue much more quickly.

Speaking of fatigue, my final project for the nutrition class was to prepare for a debate arguing the merits of branched chain amino acid (BCAA) supplements. I approached my topic with a lot of skepticism (I'm skeptical about any supplement or product aimed at athletes), but I found, to my surprise, a growing body of scientific evidence that supports BCAA supplementation.

BCAAs seem to have a positive effect ameliorating central fatigue. Central fatigue is fatigue that affects the central nervous system (what I'll call c-fatigue), but its causes and the possible mechanisms involved are not well understood. There's also peripheral fatigue (or p-fatigue) that originates in the muscles. With p-fatigue, the muscles use glycogen (stored glucose) and blood glucose for energy via the Krebs cycle. Your glycogen stores are limited so once these stores have been exhausted during a workout or competition, your body will break down muscle tissue to amino acids for more energy. Insulin comes into play here; as I understand it, insulin breaks down stored lipids into free fatty acids (FFAs) for energy use. (They can also come from digested food.)

One working theory regarding the cause of c-fatigue relates to p-fatigue. Many amino acids are released after the catabolism of muscle tissue; among these free amino acids are the BCAAs and tryptophan. Tryptophan is an essential amino acid and a precursor for 5-hydroxytrytamine (5-HT), or as it is commonly called, serotonin. The brain converts tryptophan to serotonin. One of serotonin's many effects on the brain is sleepiness.

After you finish exercising and feel exhausted, FFAs and tryptophan are released into the blood. The protein transporter, albumin, carries both of these molecules, but albumin will prefer to bind to FFAs over tryptophan. So you have a lot of tryptophan circulating in the blood.

At the barrier between the brain and blood, there are protein transporters that will take in both BCAAs and tryptophan. The theory goes that with more free BCAAs circulating in the blood, they will outcompete tryptophan for these transporters and decrease the amount of serotonin in the brain, thus relieving the strength of c-fatigue.

BCAAs supplements are as easily digestible as other amino acids, comparable to how the body quickly absorbs a sugar-and-electrolyte solution for hydration. So with greater uptake of BCAAs, you would have more BCAAs in your blood and decrease the brain's uptake of tryptophan. This is the reasoning behind using these supplements and the evidence used to support it.

There are, of course, some flaws and problems with all of this, chief among them is that the scientific evidence surrounding c-fatigue is still limited. The reason for this is that scientists can have great difficult measuring brain chemistry. There are published studies that show BCAA supplementation has little or no effect on muscle catabolism. Another argument is that muscles use 6 essential amino acids for anabolism of which BCAAs constitute only 3 of them.

At the moment the evidence is leaning toward BCAA use, but as with any supplementation, caution is the word.

Tags: nutrition, supplements

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