Posted by Larry Hoover on November 1, 2003, at 11:36:30
In reply to L-tyrosine with carbo or proteins ? , posted by Francesco on October 31, 2003, at 13:38:04
> I found what follows on an italian article.
>
> Se la tirosina viene assunta con carboidrati complessi e quindi a medio-basso indice glicemico, i livelli dell'aminoacido possono incrementare in modo significativo, in quanto si abbassano i livelli degli aminoacidi competitori della tirosina. Un pasto solo proteico, pur innalzando i livelli serici di tirosina, non sembra far aumentare tuttavia la sintesi dei neurotrasmettitori
>
> It says that if you take tyrosine with complex carboidrates (pasta and so on) this leads to an increase of the dopamine and NE, because complex carboidraites lowers at the same time the level of the competitor aminoacids. But if you take it with protein this doesn't result in an increase of dopamine and NE (even if the level of tyrosine gets higher).
>
> Have some of you heard before something like this ?Your quotation describes a process that contradicts my understanding of what happens.
Tyrosine is one of five amino acids that compete for transport into the central nervous system (across the so-called blood/brain barrier), via the LNAAT (Large Neutral Amino Acid Transporter). If I recall correctly, the five are tyrosine, phenylalanine, leucine, isoleucine, and tryptophan. They each have slightly different affinities for the transporter, so if found in the blood at equal concentrations, the one(s) with the higher affinity will have an advantage, and be transported into the brain more efficiently. Tryptophan has the lowest affinity of the five, and it is found in relatively low concentrations in all proteins, so it tends to lose the competition relative to the others.
What you want to do, to increase the availability of a particular amino acid to the brain, is control the relative concentrations of the aminos in the blood.
One of the ways to do that is to consume a pure amino acid product. If taken on an empty stomach (four hours after a meal, but best in the morning at least one half hour before breakfast, due to the fasting that occurs during sleep), it stands to reason that a pure amino will have substantial uptake from the stomach (it is "predigested"). It will thus be in substantially higher blood concentration than any other aminos, as they have already been removed from the blood by tissues which require them during the fasting stage between meals. It's like a busload of people entering a fast food restaurant at the same time. Other people entering the restaurant at the same time are going to have a harder time getting service. You want to flood the transporter, so it really doesn't have much "choice" about which amino it will pump into the brain.
Now, about the carbo thingie. Insulin regulates more than blood sugar. It also regulates amino acid uptake by muscles. When insulin goes up, muscles take up glucose *and* amino acids, but with one exception. Muscles don't need much tryptophan. Tryptophan concentrations stay stable, while the others go down. So, my understanding is that carb intake will *reduce* tyrosine availability to the brain, while simultaneously enhancing tryptophan availability. Dopamine and norepinephrine lose, serotonin wins.
That is one of the theories behind carb craving by depressives.....an intuitive attempt at self-medication, via promotion of tryptophan uptake by the brain.
I'm not saying I'm right.....just be careful of things you read. Find confirmation of *any* advice you may receive, including mine.
Lar
poster:Larry Hoover
thread:275292
URL: http://www.dr-bob.org/babble/alter/20031023/msgs/275500.html