BCAAs vs free-form amino acids in diet.

[silligcam]

I looked all over the internet and cant seem to find a good answer on this, a biologist has to know.

I work out. I take a whey protein supplement. The whey protein is made of branched chain AAs. On the back of the can, it has a chart of the typical amino acid masses that are in the average serving. For example, it says that there is 450mg of Tryptophan per serving.

When Tryptophan is taken in its free-form, 450mgs would have very noticable mental effects because my body would convert it into serotonin. However, when I take the tryptophan, as a BCAA in the whey, there are no mental effects.

Someone told me that free-tryptophan wouldn't cause mental effects. I disagree though. I'll provide this additional example though. I once took free-form l-phenylalanine (around 500mgs) which is a pre-cursor to neurotransmitters like dopamine, noradrenaline, and adrenaline. I noticed a strong mental excitation effect. Yet, there is almost a gram per serving of l-phenylalanine in the whey and I don't notice these effects.

I realize that my body uses amino acids for other chemical synthesis besides protein. It seems though, that my body would prefer to use a free-form amino acid for these non-protein purposes.

Is this true? Does the body primarily use free-form amino acids for non-protein purposes. It certainly seems that way from my experience.

Thanks for any replies!