Posted by 3 Beer Effect on May 7, 2002, at 22:18:53
In reply to L-tryosine, posted by geno on May 7, 2002, at 20:10:51
They did experiments with ADD kids where they gave them large doses of L-Tryosine which would theoretically boost their dopamine levels but the experiment had little to no effect on their ADD symptoms.
The problem with L-tyrosine is that it doesn't cross the Blood Brain Barrier. There is a carrier that transports l-tyrosine from the blood into the brain, but it is usually saturated with proteins from the diet so most supplemental l-tyrosine is metabolized & then excreted as the waste product urea/uric acid by your kidneys.
The only way supplemental l-tyrosine is good for anything is if you take an amphetamine on a daily basis. Amphetamines such as Adderall, Dexedrine, Dextrostat & their generics deplete the brain of its stores of dopamine & norepinephrine, so an adequate supply of the eventual dopamine precursor l-tyrosine may help prevent this depletion and restore released dopamine/norepinephrine.
In experiments where l-tyrosine was administered about 5 hours previous to dextroamphetamine or methamphetamine, there was an increase in the subjective effects for the l-tyrosine group that was not seen in the control group.
L-Tyrosine would probably also help improve the efficacy of dopamine/norepinephrine reputake inhibitors such as Ritalin & Concerta, although these do not deplete the brain of dopamine as much as the amphetamines. But I read in an old book that too much l-tyrosine with Ritalin can cause high blood pressure, so anyone on supplemental l-tyrosine should watch out for hypertension.
So if you don't take an ADD stimulant, supplemental L-tyrosine is basically a waste of time & money- you might feel some effect at first but that dies off after two weeks & anyways your body can make l-tyrosine from l-phenylalanine in your diet.
If you do take ADD stimulants it would probably help, but only in doses of 500 to 1500 mg/day. Higher doses are not only a waste of money but they are metabolized to inactive metabolites & excreted in your urine as excess waste & are hard on your kidneys. Also, Vitamin B6, C, & Folic Acid are essential to metabolize L-Tyrosine- not the excessive amounts advocated by some of the health food store or weightlifter people but probably about the 100% RDA of each. Also, L-Tyrosine must be taken on an empty stomach.
Personally, I've only had success with "Twinlab" brand L-Tyrosine. I take one Twinlab "L-Tyrosine Plus" which has 250 mg l-tyrosine with a whole bunch of Vitamins B6, & C; & I also take 2 of their regular Twinlab "L-Tyrosine" 500 mg capsules, along with a Folic acid 400 mcg tablet, all on an empty stomach early in the morning about an hour or two before i'm supposed to wake up in the morning.
There is the amino acid L-Phenylalanine which does have a mild stimulant/uplifting effect in some people, & it crosses the blood-brain barrier, & is a precursor to l-tyrosine but unfortunately many experiments have shown it LOWERS levels of Serotonin, Norepinphrine, & Dopamine so it is best avoided as a supplement by just about everyone (although the l-phenylalanine you derive from your food/diet is an essential amino acid).
poster:3 Beer Effect