16 replies to this topic

[babcock]

I recently started taking N-Acetyl-L-Tyrosine and now after going back and trying to find studies on it I find myself wondering why I even saved it in my iherb account to buy. I'm finding very little scientific evidence to support any positive nootropic effects. I definitely notice an effect though when I take it. It definitely boosts dopamine production in my body. I've ended up taking it about an hour or half hour before bed at night generally when I watch TV or a movie. I find it incredibly relaxing the effect being similar to that of codine (due to the dopamine I would imagine) or similar to how I feel after running a long distance/doing hard work and relaxing after showering, quite pleasant. Anyway, I threw this post up to hear anyone else's experiences with Tyrosine or to see if anyone could point me to some studies showing the benefits of L-Tyrosine supplementation since I have apparently not done my homework.

[ramon25]

From what i understand N-Acetyl-L-Tyrosine is less effective than regular old tyrosine. Yeah it definatley increases dopamine but may deplete sulfur containing amino acids in the process and may not be good without some tryptophan to balance it out later on the down the road. probably best for people who need more dopamine. i am using it to quit smoking.

Edited by ramon25, 17 June 2010 - 02:10 AM.

[chrono]

I agree with you about the effects of NALT. It gives me the warm, relaxing and diffuse feeling I associate with dopamine release. But it also clouds my higher brain functions in a way that makes it difficult to write or analyze as effectively as I'm used to.

So far all I have in my notes are papers about biosynthesis of DA. Haven't seen any human studies involving exogenous tyrosine, but I haven't looked that hard. All the experiences I read on the forum suggested in made thinking clearer and faster. Do you get this, babcock? Or do you feel kind of muddled, like I do? Somethingtoxic should have something to say about this too, he's crazy about NALT.

I couldn't find any papers involving NALT in any way. My understanding is that it works better; acetylated molecules usually cross the BBB more readily. Or at least, it requires a smaller dose; I suppose the subjective effects might be different. I grabbed 100g L-tyrosine with my last True Protein order because it was only 5 bucks, but I haven't got around to testing it out yet. I'll give it a try later in the week, and see what I can divine about the difference.

[babcock]

So far all I have in my notes are papers about biosynthesis of DA. Haven't seen any human studies involving exogenous tyrosine, but I haven't looked that hard. All the experiences I read on the forum suggested in made thinking clearer and faster. Do you get this, babcock? Or do you feel kind of muddled, like I do? Somethingtoxic should have something to say about this too, he's crazy about NALT.

The only time I tried NALT when effort was expected of me was the first day I had it before I went to work. I got to work and was really confused because I had taken my ALCAR/ALA/Piracetam combo that morning and I didn't feel like doing anything. I was completely content sitting at my desk and staring at my monitors not doing anything. I then remembered that I took the NALT and attributed the lack of motivation to that. I also decided at that point that NALT would be a good way to unwind at the end of the day (which it has been). I usually do about an hour or so of TV before bed and I've started taking the NALT before sitting down to watch it. A reason I compare it to codine is because a few months ago I had my wisdom teeth out. I got a bottle of Hydrocodones to deal with the pain. I found myself only needing advil before I left for the day and during the day I'd be distracted enough to not notice the pain. But when I got home and was not as distracted I would notice the pain and usually take the codine before watching TV. The effect was almost identical(but not as strong) as that of NALT. When I would take the codine and lay down on the couch I would "lose" feeling of my appendages. Not like a tingling sensation or anything like that but unless I was consciously trying to move my limbs it would feel as if they weren't part of my body. This is the same effect I get with 700mg of NALT.

Back to the clearer and faster thinking I completely agree with you from my one experience at work and my experiences at home. I doubt this would make me think faster or clearer as when I take it I just feel like zoning out and doing something low key/low effort (watching TV). The only thing I can think of is people who suggest it helps them think clearer or faster might be hyper-tensive or have ADD/ADHD to a point where this mellows them out so their brain isn't constantly racing. I personally don't have that problem and am always completely relaxed and low muscle tone (i.e. slouching, calm, etc.)

That's mainly why I started this thread because I guess even when I ordered it I thought Tyrosine had some neuroprotective benefits but now I realize I must have completely made that up. I definitely like the effect the supp has but I doubt I'll keep taking it after I run out unless I see some studies on neuroprotection.

I couldn't find any papers involving NALT in any way. My understanding is that it works better; acetylated molecules usually cross the BBB more readily. Or at least, it requires a smaller dose; I suppose the subjective effects might be different. I grabbed 100g L-tyrosine with my last True Protein order because it was only 5 bucks, but I haven't got around to testing it out yet. I'll give it a try later in the week, and see what I can divine about the difference.

Yea I was surprised to hear ramon25's response that NALT is less effective than L-Tyrosine because from what I had read (somewhere, maybe I made that up too) L-Tyrosine doesn't readily cross the BBB and that's why you have to bind it. Will be interesting to see if you experience anything/anything different with the L-Tyrosine.

[chrono]

The only thing I can think of is people who suggest it helps them think clearer or faster might be hyper-tensive or have ADD/ADHD to a point where this mellows them out so their brain isn't constantly racing. I personally don't have that problem and am always completely relaxed and low muscle tone (i.e. slouching, calm, etc.)

I have inattentive ADD pretty bad, and NALT does help in a certain way. It's astonishingly difficult for me to perform tasks which a) I'm not super-interested in and excited about, and b) aren't highly complex (and this includes things I actually want to do). My brain won't downshift into an appropriate gear, I don't feel engaged in what I'm doing, and consequently I don't feel rewarded, or that it makes sense to be doing those tasks. Dopaminergics usually help with this. That mental calmness makes it a lot easier to feel satisfied performing tasks with a more "menial" mental component to them. Unfortunately, at least in the case of NALT, it comes along with a certain cerebral numbness...almost like my brain feels when I'm very tired. I have a hard time making mental connections that are usually quite easy for me. I'll be trying to write something, and the appropriate words just won't come to me, and I feel like I'm writing at a much lower level than usual. So, I think it's useful for certain attentional components, but at least for me, not a "complete" solution.

Oh, and I've tried it many times in the morning with my usual dose of piracetam + ALCAR. Same thing, really...maybe these reduce the higher-order dysfunction a little bit. I think I prefered NALT without these other CEs the few times I've taken it alone; the pleasurable aspects might be more pronounced. I'll try to do this a few more times this month as well.

[babcock]

Oh, and I've tried it many times in the morning with my usual dose of piracetam + ALCAR. Same thing, really...maybe these reduce the higher-order dysfunction a little bit. I think I prefered NALT without these other CEs the few times I've taken it alone; the pleasurable aspects might be more pronounced. I'll try to do this a few more times this month as well.

The morning I took it with my ALCAR+piracetam I felt like it completely canceled out the effects of the ALCAR and piracetam. I felt as I did before I started my ALCAR routine, groggy/lethargic. Those are currently the symptoms I'm trying to rid myself of with noots.

[gamesguru]

NALT more readily navigates the blood-to-brain barrier, but it has LOWER oral bioavailability.

Utilization of tyrosine-containing dipeptides and N-acetyl-tyrosine in hepatic failure.

Druml W, Hubl W, Roth E, Lochs H.

Department of Medicine III, Vienna General Hospital, Austria.

The impact of hepatic dysfunction on the elimination and hydrolysis of three potential tyrosine sources for total parenteral nutrition, the dipeptides L-alanyl-L-tyrosine (Ala-Tyr) and glycyl-L-tyrosine (Gly-Tyr), and N-acetyl-L-tyrosine (Nac-Tyr) were evaluated in six patients with hepatic failure (five chronic, one acute) and seven healthy subjects. In controls, whole-body clearance (Cltot) of Ala-Tyr was higher than of Gly-Tyr (3,169 +/- 214 vs. 1,780 +/- 199 mL/kg/min, P < .01), and both exceeded clearance of Nac-Tyr (309 +/- 29 mL/kg/min, P > .01). Both dipeptides were hydrolyzed and released tyrosine immediately. In hepatic failure, elimination and hydrolysis of Ala-Tyr and Gly-Tyr were comparable to controls, but Cltot of Nac-Tyr was reduced (236 +/- 26 mL/kg/min). Neither in controls nor in patients an increase in plasma tyrosine concentration was seen after Nac-Tyr, and the major part of Nac-Tyr infused was lost in urine. The Cltot of tyrosine as evaluated after Ala-Tyr infusion (with the immediate release of tyrosine) was severely reduced in hepatic failure (152.7 +/- 38.4 vs. 484.4 +/- 41.4 mL/kg/min, P < .001) and half-life (kle) was retarded from 14.4 +/- 1.4 to 90.2 +/- 32.2 minutes (P < .03). The authors conclude that acute and chronic hepatic dysfunction does not affect elimination and hydrolysis of the dipeptides Ala-Tyr and Gly-Tyr and the constituent amino acids are released immediately. Nac-Tyr elimination was not grossly affected by hepatic failure, but neither in healthy subjects nor in hepatic failure patients was an increase of tyrosine seen. Both dipeptides but not Nac-Tyr may serve as a tyrosine source in parenteral nutrition. Moreover, by its rapid hydrolysis, the use of Ala-Tyr, for the first time, enables a simple rapid nonisotope evaluation of tyrosine kinetics for assessment of liver function.

I've taken 2-3 g of tyrosine powder before, and the results set in from about 20-40 minutes +T0. It is similar to, though milder than, adderall. It allows one to focus more intently on a complex task, but makes simple...sometimes desirable tasks less appealing. It motivates you to do your hardest homework first in less time than ever, or take a hard test pretty well. But on a daily basis to study an intellectual passion, I can't recommend it.

Edited by dasheenster, 21 June 2010 - 02:42 AM.

[chrono]

Good find. Don't know why I couldn't find any studies before. I did the search the day I bought (and tried) NALT along with L-theanine, so case in point, I guess.

There seems to be some conflicting data concerning NALT's usefulness. Several papers agree with the one dasheenster posted (Hepatology. 1995 Apr;21(4):923-8), that NALT isn't good at raising plasma TYR levels, and has limited bioavailability and usefulness:

Aromatic amino acid metabolism of neonatal piglets receiving TPN: effect of tyrosine precursors.
Wykes LJ, House JD, Ball RO, Pencharz PB.

...The high urinary excretion of N-AcTyr (65%) confirms its low bioavailability...

PMID: 7977717 [PubMed - indexed for MEDLINE]

Utilization of tyrosine dipeptides and acetyltyrosine in normal and uremic humans.
Druml W, Lochs H, Roth E, Hübl W, Balcke P, Lenz K.

...In CON, whole body clearance (Ctot) of Ala-Tyr (3,169 +/- 198 ml/min) was higher than Gly-Tyr (1,781 +/- 184, P less than 0.001), and both exceeded NAc-Tyr (284 +/- 24, P less than 0.001). In HD, Ctot of Ala-Tyr was not different from CON, but Ctot of Gly-Tyr (858 +/- 73, P less than 0.001) and NAc-Tyr (129 +/- 30, P less than 0.02) was decreased...Plasma Tyr did not increase with NAc-Tyr in either group. Urinary loss of peptides was neglible, but 60% of NAc-Tyr infused was excreted by CON. ...These differential effects on peptide assimilation underscore the importance of peptide structure on metabolism. Both peptides, but not NAc-Tyr, may serve as a nutritional substrate in renal failure patients.
PMID: 1996632 [PubMed - indexed for MEDLINE]

While others conclude the opposite, suggesting that it is effective at raising plasma tyrosine levels, and is useful for the purpose of parenteral nutrition:

Amino acid solutions for premature neonates during the first week of life: the role of N-acetyl-L-cysteine and N-acetyl-L-tyrosine.
Van Goudoever JB, Sulkers EJ, Timmerman M, Huijmans JG, Langer K, Carnielli VP, Sauer PJ.

Tyrosine and cyst(e)ine are amino acids that are thought to be essential for preterm neonates. These amino acids have low stability (cyst(e)ine) or low solubility (tyrosine) and are therefore usually present only in small amounts in amino acid solutions. Acetylation improves the stability and solubility of amino acids, facilitating a higher concentration in the solution...On postnatal day 7, plasma amino acids were measured together with urinary excretion of amino acids and the total nitrogen excretion; 38% of the intake of N-acetyl-L-tyrosine and 53% of the intake of N-acetyl-L-cysteine were excreted in urine. Plasma levels of N-acetyl-L-tyrosine (331 +/- 74 mumol/L) and N-acetyl-L-cysteine (18 +/- 29 mumol/L) were higher than those of tyrosine (105 +/- 108 mumol/L) and cystine (11 +/- 9 mumol/L), respectively. Plasma tyrosine levels in the groups receiving small amounts of tyrosine remained just below the reference range. We show a linear correlation of plasma cystine with the intake of cysteine (r = .75, p = 0.01), but not with N-acetyl-L-cysteine...

PMID: 7815670 [PubMed - indexed for MEDLINE]

N-acetyl-L-tyrosine as a tyrosine source in adult parenteral nutrition.
Hoffer LJ, Sher K, Saboohi F, Bernier P, MacNamara EM, Rinzler D.

...RESULTS: Approximately 35% of administered NAT was excreted unchanged in the urine, with no important effect of infusion rate, N balance, or level of renal function on this value. Sufficient NAT was retained that the prescription of 1 g total amino acids/kg x day(-1) using this product exceeded the combined recommended dietary allowance for aromatic amino acids

PMID: 14621123 [PubMed - indexed for MEDLINE]

N-acetyl-L-tyrosine and N-acetyl-L-cysteine as tyrosine and cysteine precursors during intravenous infusion in humans.
Magnusson I, Ekman L, Wångdahl M, Wahren J.

Eleven healthy volunteers were given 5 g of either NAT or NAC as a 4-hour intravenous infusion. Plasma levels of NAT and NAC increased rapidly, accompanied by a 25% increase in tyrosine levels and a 35% decrease in total cysteine. Urinary excretion of NAT and NAC in 4 hours accounted for 56% and 11% of the infused amount, respectively. No net production of tyrosine or cysteine was found from the splanchnic area, but from the kidneys there was a small release of both tyrosine (10 +/- 3 mumol/min) and cysteine (64 +/- 3 mumol/min). We conclude that under these conditions the usefulness of NAT and NAC as precursors for the corresponding amino acids in humans is not apparent.

PMID: 2507878 [PubMed - indexed for MEDLINE]

Utilization of N-acetyl-L-tyrosine and glycyl-L-tyrosine during long-term parenteral nutrition in the growing rat. [free text]
Neuhäuser M, Wandira JA, Göttmann U, Bässler KH, Langer K.

...No differences in weight gain or N-balance could be detected as a result of administering either the solution with glycyl-L-tyrosine or with N-acetyl-L-tyrosine in place of the solution containing an adequate phenylalanine content. Daily urinary excretion rates for N-acetyl-L-tyrosine and glycyl-L-tyrosine were 11% and 0.5%, respectively, of the infused amount. Plasma amino acid pattern was affected differently by the four solutions. The results indicate that both N-acetyl-L-tyrosine and glycyl-L-tyrosine are efficiently utilized by the rat during total parenteral nutrition.

PMID: 3931451 [PubMed - indexed for MEDLINE]

N-acetyl-L-tyrosine as a tyrosine source during total parenteral nutrition in adult rats.
Im HA, Meyer PD, Stegink LD.

...Infusion of N-acetyl-U-14C-L-tyrosine as part of a total parenteral nutrition regimen in the rat at a level of 0.5 mmol/kg/day resulted in rapid labeling of tissue tyrosine pools, production of 14CO2, incorporation of 14C-labeled tyrosine into protein, and modest urinary losses (8.3%). Plasma tyrosine levels, however, remained at fasting values (73.8 +/- 5.40 microM). Infusion of N-acetyl-L-tyrosine at 2 mmol/kg/day increased plasma tyrosine above fasting levels (141 +/- 16.1 microM), resulted in a rapid labeling of tissue tyrosine pools, production of 14CO2, and incorporation of 14C-labeled tyrosine into protein. However, urinary losses were higher (16.8%). Rapid utilization of N-acetyl-L-tyrosine was noted at both infusion levels. Plasma- and tissue-free tyrosine pools were rapidly labeled, as was tissue protein. Radioactivity incorporated in tissue protein was shown to be tyrosine after acid hydrolysis.

PMID: 3925425 [PubMed - indexed for MEDLINE]

But it should be noted that most of this data doesn't necessarily have any bearing on what we're using it for. Plasma levels and physiological AA requirements are not the same as getting it to the brain, and utilized effectively to increase dopamine. Z Ernahrungswiss. 1982 Mar;21(1):21-6 mentions that NALT is deacetylated primarily in the kidney, and also liver.

This is the only study I came across tonight mentioning NALT in the context of brain levels. The abstracted conclusion is somewhat imprecise, but seems to suggest that the phospho- and methyl- tyrosines were as effective as normal tyrosine at raising brain levels, and NALT was less so:

Brain tyrosine increases after treating with prodrugs: comparison with tyrosine.
Topall G, Laborit H.

After mice had been treated with L-tyrosine, O-phospho-L-tyrosine, L-tyrosine methyl ester or N-acetyl-L-tyrosine, tyrosine was assayed by HPLC coupled with fluorometric detection. O-Phospho-L-tyrosine behaved as a tyrosine prodrug after its hydrolysis by acid and alkaline phosphatases. After the intraperitoneal administration of O-phospho-L-tyrosine or the methyl ester, there was a substantial increase in bioavailability in terms of the effect of tyrosine. The two prodrugs were as powerful as tyrosine following oral administration. N-Acetyl-L-tyrosine was the least effective prodrug tested. The stability, solubility and bioavailability of O-phospho-L-tyrosine are consistent with proposing it for use as a tyrosine prodrug. In addition, it can be used parenterally. The use of a tyrosine aminotransferase inhibitor is necessary for limiting the hepatic breakdown of tyrosine and for increasing its bioavailability.
PMID: 2576051 [PubMed - indexed for MEDLINE]

(tyrosine aminotransferase inhibition for increasing bioavailability might be worth investigating further)

I think it's quite possible that NALT's increased ability to cross the BBB more than makes up for the lesser bioavailability. Indeed, in light of the fact that several members here (myself among them) report very strong effects from NALT in the 350-700mg range, I think it's quite probable. I'm pretty daring, and taking 2-3g of NALT seems somewhat reckless to me.

I've taken 2-3 g of tyrosine powder before, and the results set in from about 20-40 minutes +T0. It is similar to, though milder than, adderall. It allows one to focus more intently on a complex task, but makes simple...sometimes desirable tasks less appealing. It motivates you to do your hardest homework first in less time than ever, or take a hard test pretty well. But on a daily basis to study an intellectual passion, I can't recommend it.

This is in line with many of the tyrosine experiences I've read here. However, I would describe my experience with NALT to be just the oposite: highly complex tasks are very difficult to focus on, but motivation and appreciation for simpler, non-intellectual pleasures is increased.

Something I didn't consider until now is the possibility that NALT produces effects distinct from L-tyrosine. For instance, ALCAR has many different effects in several systems than the non-acetylated L-carnitine. However, since NALT isn't an endogenous substance, I assumed that the only difference was in the pharmacokinetics of tyrosine delivery, and enhanced ability to cross the BBB.

Now I'm wondering if NALT possesses a characteristic or mechanism which might account for this subjective difference in experience. As most of the 49 papers in medline deal either with nutrition or chemistry, I'm unsure how to confirm this hypothesis. I'll start trying NALT and L-tyrosine more myself now that I'm considering this possibility (until now, I've considered NALT a quasi-recreational pseudo-nootropic that I've seldom been in the mood for). Hopefully others will chime in, and we can collect some more data about this.

Edited by chrono, 21 June 2010 - 07:22 PM.

[Guacamolium]

I suspected that NALT had at least a marginally small difference in effects to L-tyrosine, much like L-carnitine works differently than ALCAR, for example. Unfortunately I think I tossed my L-tyrosine out because it was around 5 years old, and I have enough NALT to last for quite a while, so while it would've been nice to subjectively compare the effects of the two, I would have to buy a cheap bottle of L-tyrosine on my next supplement purchase. I remember them to be similar in effects, but I prefer NALT because it's water soluble and the dose is lower. L-tyrosine was better for putting in smoothies before a workout, but I could do that with NALT anyway.

Props to you Chrono for posting those studies! I contacted Source Naturals last month or so about their claim - "N-Acetyl L-Tyrosine is a more rapidly absorbed and bioavailable form of the amino acid L-tyrosine, and is less prone to urinary excretion. - which Jarrow and purebulk.com also made, but Source Naturals never responded back.

Anyway - I take 2-4 grams of L-tyrosine if I have it, and 205mgs of NALT usually now, and I can't even imagine what 2-4 grams of NALT would feel like - probably like a complete panic attack or something. I've taken 1 gram before, and I was way too on edge.

If the two do actually have different effects, then they are marginally different, at least with me. I did notice though that I could take high doses of LT (5g+) with less of that edgy feeling, for what it's worth. I do suspect that this LT versus NALT subject will continue for quite a while though.

[babcock]

Anyway - I take 2-4 grams of L-tyrosine if I have it, and 205mgs of NALT usually now, and I can't even imagine what 2-4 grams of NALT would feel like - probably like a complete panic attack or something. I've taken 1 gram before, and I was way too on edge.

Huh, NALT really must affect people differently, when i take it I take 700 mg and it just mellows me right out.

[Guacamolium]

Anyway - I take 2-4 grams of L-tyrosine if I have it, and 205mgs of NALT usually now, and I can't even imagine what 2-4 grams of NALT would feel like - probably like a complete panic attack or something. I've taken 1 gram before, and I was way too on edge.

Huh, NALT really must affect people differently, when i take it I take 700 mg and it just mellows me right out.

Well, cognitive enhancers across the board affect people in various ways. For instance, primary cholinergics that I've seen here over 3 years from people's experiences have shown it to range from an actual cognitive enhancer, to the opposite effect, to nothing.

I've taken around 700mgs before, but with things like pyritinol, MPH, ALCAR, and well, all kinds of CE'rs. I always thought of it as an ancillary cognitive enhancer to help boost the more primary ones. As a standalone, I'd have to try 700mgs by itself and get back to you, if that's what you were inferring. I believe FunkOdyssey also got edgy from higher doses because of a past statement he'd made probably a year ago.

Anyway, the studies were posted here, and I'll try NALT at 700mgs by itself and report back. =)

[Guacamolium]

Okay, sorry for the delay. I took as close to 712mgs as I could measure without a precise mg scale on hand. Did it three consecutive days in fact without anything else that could change a variable substantially, and it was a tad edgy for me, but I got that "determined" feeling of motivation for all three days. I noticed a short duration of mental calmness on the third day.

[chrono]

I've been playing around with L-tyrosine a couple of times a week. So far, my observation is that there are some definite differences.

I don't seem to tolerate 2-3g dosages very well; at least, not consistently. It gives me a strange feeling in the upper-front of my brain; not a headache, but almost like pressure, like something's not letting me think properly. It's more dopaminergic, but this feeling of almost mental numbness makes it difficult to enjoy.

1-1.5g works much better. Gives me a slight dopamine boost, but not the relaxing kind that L-DOPA or NALT gives me, and may actually improve my thinking ability slightly (or at least, doesn't interfere to the extent of the other two).

I'll keep trying these throughout the summer, in different circumstances.


@somethingtoxic: thanks for the follow-through. That dosage of NALT doesn't carry any edginess for me, perhaps due to dopamine deficiency. I hope you can grab like $5 worth of L-TYR sometime when you're placing an order, and report on what the difference is.

[juverulez]

I just recently switched from L tyrosine powder to nalt capsules and the difference is absolutely fantastic... Just one capsule does wonders for me confidence, self-esteem even. Definietely gives you a boost, I take myprotein nalt which is 250 nalt plus vitamin b6.

Oh yeah, just one more thing: probably the biggest pro of nalt is that compared to regular tyrosine it doesn't make me edgy at all... Which makes it a superb choice for me as I struggle with anxiety. I've only been taking it for two days so far but will let you know if I get a different reaction.

Edited by juverulez, 24 July 2010 - 07:05 PM.

[The Likud Is Behind It]

Sorry I didn't read the whole thread. I found the extra strength 5 hour energy supplement contains NALT. I used to use regular l-tyrosine, but I've dropped it recently because I don't exactly need the extra catecholamines. The extra strength gives me a huge boost of energy. I'm almost going to experiment with it, but I really don't need the energy in general. It can be too stimulating. I don't want to downregulate my receptors.

Edited by bmud, 28 July 2010 - 03:09 AM.

[Thorsten3]

Sorry I didn't read the whole thread. I found the extra strength 5 hour energy supplement contains NALT. I used to use regular l-tyrosine, but I've dropped it recently because I don't exactly need the extra catecholamines. The extra strength gives me a huge boost of energy. I'm almost going to experiment with it, but I really don't need the energy in general. It can be too stimulating. I don't want to downregulate my receptors.

Yeah that's what worries me about taking these amino acids in large quantities. I did notice after a while that tyrosine/phenylalanine woulod become less effective. Plus where it was so stimulating I found it a bit crude in its effects (like it was pushing serotonin to one side). It can be pretty cool if that's the effect you are after. But I would doubt the long term efficiency due to tolerance (is that down to reduction of tyrosine hydroxylase? - i'm not sure tbh).
I would prefer something like SAM-e which I find quite stimulating (when I've taken it).

[kilgoretrout]

I guess the property of crossing BBB faster, giving a steeper slope to a chart of brain-tyrosine-concentration...

and thus all the down stream neurotransmitters also have a MORE RAPID RATE OF INCREASE inside the brain...

seems like that could definitely create a different subjective sensation.

Still seems weird... plausible but weird. I'll have to give it a try. I've been a big fand and very frequent daily user of plain tyrosine for decades, so if anyone i should definitely notice a difference. I'll report back here soon as I try it.... hmmm... Gold Card week at GNC, so perhaps soon.