L-Glutamine

r u sure about this or is this just a supposition. I know you're sure about what you read on PubMed, but when you say "this suggest it aids in synapse firing..." I am hopeful, but think we gotta do more research. Just cause glutamine turns into glutamate doesn't mean the brain will suddenly manufacter more glutamate than usual just cause the bodies supply increased. Also, glutamate is a double edged sword neurotransmitter -- I'm always a little leery in upregulating glutamate cuz of the excitotoxicity possibility.

From all that I have read it is a fact that glutamine, as a key neurotransmitter, increases the function of the brain. Glutamine is a more common neurotransmitter than GABA even, but keep in mind it is an excitotoxin, meaning an over-abundance of this in your system can be harmful. I make no disclaimers about its safety - I was just talking about a common reason to use it. It also increases the quantity of GABA in the brain. To answer your question, there may be cases where increasing the amount of glutamate in your body may cause excitoxicity but they seems to be a) rare and b) only in excessive quantities.

Keep in mind it's not uncommon to ingest a 5 - 10 grams of glutamine a day in your diet, so you can't really AVOID it completely anyway - hence i'm sure your body won't start melting synapses etc. just because you had 2 beef steaks for dinner instead of one

Robbie

GLUTAMINE HAS NO VALUE IN HEALTHY PEOPLE WHATSOEVER.

Glutamine production in muscle protein is 50% lower than assumed
-Results of tracer studies indicate that skeletal muscle contributes to approximately 70% of overall glutamine production in healthy adults; the contribution of de novo synthesis being estimated at approximately 60%. Direct and specific measurements of glutamine in intact muscle protein are 50% lower than assumed previously (G1).

Most amino acids are precursors for alanine and glutamine synthesis in skeletal muscle
-Cysteine, leucine, valine, methionine, isoleucine, tyrosine, lysine, and phenylalanine increase the rate of glutamine synthesis. The progressive decline in alanine and glutamine synthesis noted on prolonged incubation is prevented by the addition of amino acids to the incubation medium (G2)

Little evidence of glutamine deficiency in humans and a role for supplementation
-Although glu-tamine is generally recognized to be safe on the basis of relatively small studies, side effects in patients receiving home parenteral nutrition and in those with liver-function abnormali-ties have been described. Therefore, on the basis of currently available clinical data, it is inappropriate to recommend gluta-mine for therapeutic use in any condition.
There is little confirmatory evidence of glutamine deficiency in humans and of a role for either glutamine replacement therapy or pharmacologic doses of glutamine. Decreased blood concentrations of glutamine do not necessarily indicate a deficient state, as is the case with other nutrients. The loss of amino acids from skeletal muscle is not specific to glutamine (G51).

Nutritional depletion does not determine glutamine concentrations
Glutamine supplementation may not even effect plasma and mucosal glutamine concentrations at all. There are concflicting results and the reason for this has not been clarified yet. Major changes in glutamine metabolism take place during inflammatory stress and glutamine supplementation has been most successful under these circumstances. Nutritional depletion per se does not affect glutamine concentrations (G52).

90% of the glutamine you take orally never even makes it to your muscles. Glutamine supplementation decreases it's own synthesis and mostly turns itself into glucose.
-Systemic glutamine administration is ineffective in preventing muscle depletion, due to a relative inability of skeletal muscle to seize glutamine from the bloodstream. Transport from blood accounts for only 25% of the intramuscular glutamine pool turnover. In contrast, the intracellular pools of most essential amino acids, such as phenylalanine or leucine, derived largely from the extracellular space. Studies involving oral ingestion of stable isotope-labelled glutamine indicate that 50-70% of enterally administered glutamine is taken up during first pass by splanchnic organs (gut and liver). (G14).
-Glutamine orally is successful in elevating plasma glutamine at the peak concentration by 46%, which suggests that a substantial proportion of the oral load escaped utilization by the gut mucosal cells and uptake by the liver and kidneys. If the entire glutamine dose had been distributed within the blood (8% body wt) and extracellular fluid (20% lean body mass) compartments, then a 3-mM rise in blood glutamine concentration might have been expected, whereas plasma glutamine concentration was only observed to rise by 0.3 mM. This might suggest that only 10% of the oral dose reached the extracellular fluid compartments (G15).
-Infusion of glutamine increases plasma glutamine concentration and turnover only threefold, formation of glucose from glutamine increased sevenfold. Furthermore, glutamine infusion decreased its own de novo synthesis (4.55 +/- 0.22 vs. 2.81 +/- 0.62 micromol x kg(-1) x min(-1);P < 0.02) (G16).

Glutamine plays no direct part in protein synthesis
A protein rich meal (3 g/kg lean beef) in 7 healthy sujects increases AAs from the splanchic bed. BCAAs accounted for more than half of total splanchic AA output. Arterial BCAA concentrations incremented 100-200%. Leg exchange of most AAs reverted from a basal net output to a net uptake which was most marked for the BCAAs. Glutamine was continuously taken up by the splanchic tissues and released by the leg tissues after the protein meal, although their rate of output from the leg declined transiently at 30-60 min. Protein intake resulted in a doubling of arterial insulin and glucagon.
After protein ingestion within 30-60 min. net uptake of the leg was observed for valine, leucine and isoleucine, and to a lesser extent for threonine, serine, glycine, tyrosine, phenylalanine, lysine, histidine, and arginine. The uptake of the BCAAs accounted for more than half of total leg AA uptake at 30-60 min, and for virtually all of the AA uptake at 90-180 min. Throughout the 3-h period of observation after protein intake, a continuous net release of alanine and glutamine was observed.
It is thus clear that the BCAAs are the major source for repletion of muscle nitrogen after protein intake (G53).

Glutamine does not prevent exercise-induced immune impairment. Carbs do. And glutamine does not influence hormonal levels
-Consuming 30-60 g carbohydrate x h(-1) during sustained intensive exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immune depression. Convincing evidence that so-called 'immune-boosting' supplements, including high doses of antioxidant vitamins, glutamine, zinc, probiotics and Echinacea, prevent exercise-induced immune impairment is currently lacking (G31).
-Intracellular glutamine concentration may not be compromised when plasma levels are decreased postexercise. In addition, a number of recent intervention studies with glutamine feeding demonstrate that, although the plasma concentration of glutamine is kept constant during and after acute, strenuous exercise, glutamine supplementation does not abolish the postexercise decrease in in vitro cellular immunity, including low lymphocyte number, impaired lymphocyte proliferation, impaired natural killer and lymphokine-activated killer cell activity, as well as low production rate and concentration of salivary IgA (G32).
-Glutamine supplementation abolished the postexercise decline in plasma glutamine concentration but had no effect on lymphocyte trafficking, NK and lymphokine-activated killer cell activities, T cell proliferation, catecholamines, growth hormone, insulin, or glucose (G33).
-Nutritional supplementation with glutamine abolishes the exercise-induced decline in plasma glutamine, but does not influence post-exercise immune impairment. However, carbohydrate loading diminishes most exercise effects of cytokines, lymphocyte and neutrophils (G34).

Glutamine does not increase protein synthesis
-Intravenous infusion of amino acids increases the fractional rate of mixed muscle protein synthesis, but addition of glutamine to the amino acid mixture does not further stimulate muscle protein synthesis rate in healthy young men and women (G6).
-Short intravenous infusion of glutamine does not acutely stimulate duodenal protein synthesis in well-nourished, growing dogs (G8).

Glutamine prevents protein degradation but not more effectively than carbs
-0,9 g/kg glutamine during resistance training has no significant effect on muscle performance, body composition or muscle protein degradation compared to 0,9 g/kg maltodextrin (G9).
-Glutamine preserves protein synthesis in Caco-2 cells submitted to "luminal fasting", but higher glutamine doses did not enhance protein synthesis beyond control fed values. And glucose supplementation restored FSR as effi-ciently as glutamine (G10).

Carbhohydrate or BCAA supplementation prevents decrease in glutamine levels during exercise
-Carbohydrate supplementation affects positively the immune response of cyclists by avoiding or minimizing changes in plasma glutamine concentration (G11).
-Following an exercise bout, a decrease in plasma glutamine concentration can be observed, which is completely abolished by BCAA supplementation (G12).
-BCAA supplementation during a triathlon completely prevents the decrease in plasma glutamine (G13).
-7 distance runners reduced muscle gycogen. A high carb meal (80% carbs) before 60 min. exercise increases plasma glutamine. A 14 h fast before exercise does not change plasma glutamine. Plasma BCAA did not change under either dietary condition (G17).

Fasting decreases glutamine transport. And supplementation during fasting does not prevent muscle loss
-During fasting, skeletal muscle exports increased amounts of glutamine (Gln) while increasing the production of this amino acid by glutamine synthetase (GS) in order to maintain the intramuscular Gln pool (G41).
-Background: One of the major activities of the enterocyte is amino acid transport, which is important not only for the organism but also for the integrity of the mucosa. Bowel rest during the postoperative period is marked by decreased calorie and protein intake with atrophy of the brush border mucosa.
Fasting for 72 hours decreases glutamine and arginine transport. Alanine MeAIB, and leucine transport were maintained (G42).
-0.35 g/kg glutamine/day does not prevent loss of lean muscle in athletes during a 12-day weight reduction program (G43).

Glutamine does not enhance performance
-6 resistance-trained men performed weightlifting exercises after ingesting 0.3 g/kg glutamine. This did not enhance performance (G22).

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