Home Ingredients L-Glutamic Acid / Glutamate
Gut Health

L-Glutamic Acid / Glutamate

Evidence Level
Preliminary
1 Clinical Trial
5 Documented Benefits
1/5 Evidence Score

L-Glutamic acid is a non-essential amino acid and the most abundant excitatory neurotransmitter in the central nervous system. Found in protein-rich foods, particularly umami foods (parmesan, soy sauce, tomatoes, mushrooms, seaweed). The salt form MSG (monosodium glutamate) is a common food additive providing umami taste. Standalone supplementation is uncommon. Swallowed glutamate is almost entirely extracted and burned by the intestine on first pass, and the blood-brain barrier does not permit net glutamate entry, so what you eat does not drive brain glutamate signalling. Put in proportion: an average adult already takes in about 13 g of glutamate a day from food protein, against roughly 0.55 g a day from added MSG.

Studied Dose Not typically supplemented as a standalone; dietary intake is already large, about 13 g/day from food protein plus roughly 1 g/day free glutamate and about 0.55 g/day added as MSG.
Active Compound L-Glutamic Acid / Glutamate / Monosodium Glutamate (MSG)

Benefits

Major Excitatory Neurotransmitter

Glutamate is the principal excitatory neurotransmitter in the CNS — activates NMDA, AMPA, kainate, and metabotropic glutamate receptors. Critical for learning, memory, synaptic plasticity. Endogenously synthesized. This is a description of the body's own glutamate, not a benefit of taking it: the blood-brain barrier is effectively impermeable to glutamate even at high blood concentrations, and its transporters run the wrong way for absorption, actively clearing glutamate out of brain fluid rather than letting it in. Brain extracellular glutamate is held near 0.5-2 umol/L while plasma sits at 50-100 umol/L.

Supported by Trial 1

Glutamine Precursor

Glutamate is the immediate precursor to glutamine (the most abundant amino acid in plasma; major fuel for enterocytes, lymphocytes, kidney). Most clinical interest is via glutamine supplementation rather than glutamate.

Neurotransmitter Substrate (GABA Synthesis)

Glutamate is the precursor to GABA (the major inhibitory neurotransmitter) via glutamic acid decarboxylase (GAD) — vitamin B6-dependent enzyme. Brain GABA synthesis depends on glutamate availability.

Umami Taste / Appetite Stimulation

Free glutamate (and inosinate, guanylate) provides umami — the savory 'fifth taste' detected by T1R1/T1R3 receptors. MSG enhances savoury flavour. Whether that translates into eating more is genuinely unsettled rather than established. In 120 adults averaging 72 years, soup enhanced with MSG and celery powder changed neither intake (198 g vs 203 g) nor liking (6.6 vs 6.7) against unenhanced soup, and adding MSG and/or flavouring to nursing-home meals for 16 weeks changed neither energy intake nor body weight. Against that, 40 adults aged 65-88 ate significantly more of a novel-flavoured soup after it had been paired with a high dose of MSG (123 g rising to 164 g), without liking it more. Directions conflict in younger adults too: an MSG broth preload lowered subsequent energy intake in middle-aged women, while an MSG-seasoned high-protein meal raised intake at the next course.

Supported by Trial 1

Energy Substrate

Glutamate enters the TCA cycle via alpha-ketoglutarate. For glutamate you actually swallow this happens overwhelmingly in the intestinal lining rather than elsewhere in the body: almost all dietary glutamate is extracted and oxidised by the gut on first pass, making it the mucosa's principal fuel. Most of the quantitative work behind this is in piglets, and no trial has shown that adding supplemental glutamate improves a gut outcome in people.

Supported by Trial 1

Mechanism of action

1

Excitatory Neurotransmission

Glutamate released from presynaptic neurons activates ionotropic glutamate receptors (NMDA, AMPA, kainate) — opens ion channels (Na+, Ca2+ influx). Excessive glutamate causes excitotoxicity — cell death from calcium overload; major mechanism of neuronal death in stroke, TBI, ALS.

2

Glutamine Synthesis

Glutamine synthetase (in astrocytes especially): glutamate + NH3 + ATP → glutamine. Critical for ammonia detoxification and amino acid transport.

3

GABA Synthesis

Glutamic acid decarboxylase (GAD, requires PLP/vitamin B6): glutamate → GABA + CO2. Inhibitory neurotransmitter for CNS balance.

4

Umami Receptor Activation

Free glutamate (not protein-bound) activates T1R1/T1R3 heterodimer taste receptors on the tongue, plus mGluR1 and mGluR4 — perceived as umami/savory.

5

Excitotoxicity (Pathological)

Sustained glutamate elevation (stroke ischemia, TBI, status epilepticus) causes massive NMDA receptor activation → calcium overload → mitochondrial dysfunction → neuronal death. This cascade is driven by glutamate released from injured tissue inside the brain, behind a barrier that swallowed glutamate does not cross in net amounts. It is a target for prescription drugs, not a consequence of eating glutamate: dietary and supplemental intake do not feed it.

Clinical trials

1
Double-Blind Placebo-Controlled Multiple-Challenge Study of Reported MSG Reactions (Geha 2000)
PubMed

Multicenter, double-blind, placebo-controlled crossover challenge study run across four sequential protocols (A-D); MSG was given without food in protocols A-C and with food in protocol D. Geha RS et al., J Allergy Clin Immunol 2000;106(5):973-80.

130 self-selected adults who reported reacting adversely to MSG.

With 5 g of MSG taken without food, 50 of 130 participants (38.5%) reported two or more symptoms after MSG but not after placebo, while 17 (13.1%) reacted to placebo but not MSG (p<0.05) and 19 (14.6%) reacted to both. The response did not hold up on retesting: only 19 of 37 who reacted to MSG but not placebo in the first protocol did so again in the second, and of two participants who reacted consistently across the food-free protocols, both responded to only one of three MSG challenges once food was present. The authors concluded that large food-free doses may elicit more symptoms than placebo in people who believe they react to MSG, but that responses were not reproducible and no persistent or serious effects were seen. For scale, a typical serving of a food with added MSG contains under 0.5 g.

Side effects and drug interactions

Common Potential side effects

MSG sensitivity: transient, generally mild headache, flushing, numbness, tingling or drowsiness reported by some people who take 3 g or more of MSG at once without food — well above the under-0.5 g in a typical seasoned serving. This is real but dose- and context-dependent. Double-blind challenges do find more symptoms after a large food-free dose than after placebo, and five days of 150 mg/kg MSG in soda produced significantly more nausea and headache than salt control along with a small rise in blood pressure. The same individuals usually fail to react again on retesting, and doses taken with a meal have not produced reproducible symptoms: 71 subjects given 1.5-3.15 g with breakfast responded no more often than to placebo. FDA considers added MSG generally recognized as safe (GRAS) at normal food levels.
Excitotoxicity is a pathological process in stroke/TBI — not relevant to typical dietary intake.
GI distress at very high doses uncommon.

Important Drug interactions

Memantine (NMDA antagonist) — theoretical interaction; not established at dietary levels.
Lamotrigine and other glutamate-modulating anticonvulsants — theoretical interaction; not established.
Vitamin B6 — required for GAD enzyme; B6 deficiency impairs GABA synthesis from glutamate.

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Frequently asked questions about L-Glutamic Acid / Glutamate

What is glutamic acid used for?

Glutamic acid (glutamate) is a non-essential amino acid and the body's main excitatory neurotransmitter, also important for metabolism and as a building block of proteins and glutathione. It is rarely worth taking as a standalone supplement: the body makes its own, protein foods supply many times more than any capsule, and swallowed glutamate is consumed by the intestine rather than reaching the brain.

Is glutamic acid the same as MSG?

Glutamic acid is the amino acid; MSG (monosodium glutamate) is its sodium salt used as a flavor enhancer. The body handles dietary glutamate from food protein and MSG similarly. Glutamic acid is naturally abundant in many protein foods.

How much glutamic acid should I take?

It is rarely supplemented alone, since the body makes it and it is plentiful in protein foods. When included in formulas, follow product labeling. Glutamine, a related compound, is more commonly supplemented for gut and recovery.

Is glutamic acid safe?

As a normal dietary amino acid it is generally safe. Some people report sensitivity to large amounts of free glutamate (as in MSG), though controlled studies are mixed. Those with such sensitivity may prefer to moderate intake.

What is L-Glutamic Acid / Glutamate?

L-Glutamic acid is a non-essential amino acid and the most abundant excitatory neurotransmitter in the central nervous system. Found in protein-rich foods, particularly umami foods (parmesan, soy sauce, tomatoes, mushrooms, seaweed).

What is L-Glutamic Acid / Glutamate used for?

L-Glutamic Acid / Glutamate is researched primarily for Gut Health. Glutamate is the principal excitatory neurotransmitter in the CNS — activates NMDA, AMPA, kainate, and metabotropic glutamate receptors. Critical for learning, memory, synaptic plasticity. Endogenously synthesized.

What is the recommended dosage of L-Glutamic Acid / Glutamate?

The clinically studied dose is Not typically supplemented as a standalone; dietary intake is already large, about 13 g/day from food protein plus roughly 1 g/day free glutamate and about 0.55 g/day added as MSG. Always follow the product label and check with a healthcare provider for personal advice.

Is L-Glutamic Acid / Glutamate safe, and does it have side effects?

For most healthy adults, L-Glutamic Acid / Glutamate is well tolerated at studied doses. Reported effects can include: MSG sensitivity: transient, generally mild headache, flushing, numbness, tingling or drowsiness reported by some people who take 3 g or more of MSG at once without food — well above the under-0.5 g in a typical seasoned serving. This is real but dose- and context-dependent. It may also interact with some medications. L-Glutamic Acid / Glutamate is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does L-Glutamic Acid / Glutamate interact with any medications?

Possible interactions include: Memantine (NMDA antagonist) — theoretical interaction; not established at dietary levels. Lamotrigine and other glutamate-modulating anticonvulsants — theoretical interaction; not established. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for L-Glutamic Acid / Glutamate?

NutraSmarts rates the evidence for L-Glutamic Acid / Glutamate as Preliminary (1 out of 5). It is backed by 1 clinical trial and 16 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(16 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Reiner A, Levitz J Glutamatergic Signaling in the Central Nervous System: Ionotropic and Metabotropic Receptors in Concert Neuron. 2018;98(6):1080-1098. doi:10.1016/j.neuron.2018.05.018.PubMedUsed to support: Review of central nervous system glutamate signalling, covering both the ionotropic (NMDA, AMPA, kainate) and metabotropic receptor families and describing glutamate as the mammalian brain's primary excitatory neurotransmitter and a key neuromodulator. It concerns glutamate the body produces and releases within the brain; it does not study glutamic acid taken by mouth.
  2. Andersen JV, Schousboe A Metabolic dynamics of glutamate and GABA mediated neurotransmission - The essential roles of astrocytes Journal of Neurochemistry. 2023;166(2):109-137. doi:10.1111/jnc.15811.PubMedUsed to support: Milestone review of the glutamate/GABA-glutamine cycle, describing how astrocytes recycle neurotransmitters and how glutamate serves as the precursor to GABA via glutamate decarboxylase. It describes metabolism inside brain tissue, using glutamate generated locally rather than absorbed from the diet.
  3. Sears SM, Hewett SJ Influence of glutamate and GABA transport on brain excitatory/inhibitory balance Experimental Biology and Medicine. 2021;246(9):1069-1083. doi:10.1177/1535370221989263.PubMedUsed to support: Review of how glutamate and GABA transporters regulate the balance between excitation and inhibition in the central nervous system, and how disturbances in that transport relate to neurological disease. It examines transporter function within brain tissue and does not test dietary or supplemental glutamate.
  4. Tarasoff L, Kelly MF Monosodium L-glutamate: a double-blind study and review Food and Chemical Toxicology. 1993;31(12):1019-1035. doi:10.1016/0278-6915(93)90012-n.PubMedUsed to support: In 71 healthy adults given MSG at 1.5, 3.0 and 3.15 g per person before a standardised breakfast in a randomised double-blind crossover design, most reported no response to either placebo (86%) or MSG (85%), and sensations previously attributed to MSG occurred no more often than after placebo. Dose and after-effects were negatively correlated. The authors highlight that taking MSG with food negates the effects seen with large food-free doses, and that MSG's strong taste undermined blinding in much of the earlier literature.
  5. Geha RS, Beiser A, Ren C, Patterson R, Greenberger PA, Grammer LC, Ditto AM, Harris KE, Shaughnessy MA, Yarnold PR, Corren J, Saxon A Multicenter, double-blind, placebo-controlled, multiple-challenge evaluation of reported reactions to monosodium glutamate The Journal of Allergy and Clinical Immunology. 2000;106(5):973-980. doi:10.1067/mai.2000.110794.PubMedUsed to support: In 130 adults who reported reacting to MSG, 5 g taken without food produced two or more symptoms in 50 participants (38.5%) who did not react to placebo, while 17 (13.1%) reacted to placebo but not MSG (p<0.05) and 19 (14.6%) reacted to both. Reactions were not reproducible: only 19 of 37 who responded to MSG but not placebo initially did so again on rechallenge, and the two most consistent responders each reacted to just one of three MSG challenges when food was present. The authors concluded that large food-free doses may elicit more symptoms than placebo in people who believe they are sensitive, but that no persistent or serious effects occurred and responses were inconsistent on retesting.
  6. Essed NH, van Staveren WA, Kok FJ, de Graaf C No effect of 16 weeks flavor enhancement on dietary intake and nutritional status of nursing home elderly. Appetite. 2007;48(1):29-36.PubMedUsed to support: In a 16-week randomised study of 83 nursing home residents, adding 300 mg of MSG and/or 700 mg of flavouring daily to the meat portion of the cooked meal produced no increase in energy intake or body weight in any group, and no differences between groups. The longest trial of flavour enhancement for appetite in this population, and it was null.
  7. Beyreuther K, Biesalski HK, Fernstrom JD, Grimm P, Hammes WP, Heinemann U, Kempski O, Stehle P, Steinhart H, Walker R Consensus meeting: monosodium glutamate - an update European Journal of Clinical Nutrition. 2007;61(3):304-313. doi:10.1038/sj.ejcn.1602526.PubMedUsed to support: Expert consensus placing total glutamate intake in European countries at 5-12 g/day, of which roughly 10 g is protein-bound, about 1 g is naturally free, and about 0.4 g is added as flavouring. The panel concluded that glutamate from all sources is mainly used as energy fuel in enterocytes and that the general use of glutamate salts as a food additive can be regarded as harmless for the whole population, and suggested that where appetite is decreased, as in older people, palatability can be improved by low-dose monosodium glutamate. A consensus reached by discussion among an invited expert panel rather than primary data.
  8. Bertolo RF, Burrin DG Comparative aspects of tissue glutamine and proline metabolism The Journal of Nutrition. 2008;138(10):2032S-2039S. doi:10.1093/jn/138.10.2032S.PubMedUsed to support: Reports that about two-thirds of dietary glutamine and almost all dietary glutamate are extracted on first pass, with the vast majority oxidised in the gut, and that this extraction capacity is very large — so diets high in glutamate probably have little impact on circulating concentrations. Explains why oral intake, however large, does not translate into raised blood glutamate.
  9. Essed NH, Kleikers S, van Staveren WA, Kok FJ, de Graaf C No effect on intake and liking of soup enhanced with mono-sodium glutamate and celery powder among elderly people with olfactory and/or gustatory loss International Journal of Food Sciences and Nutrition. 2009;60 Suppl 5:143-154. doi:10.1080/09637480802710216.PubMedUsed to support: In 120 adults averaging 72 years, tomato soup enhanced with MSG and celery powder produced no difference from unenhanced soup in intake (198 g vs 203 g), liking (6.6 vs 6.7) or perceived flavour strength. The null result held within the subgroup with measured low olfactory and gustatory function, the group most often assumed to benefit.
  10. Hawkins RA The blood-brain barrier and glutamate The American Journal of Clinical Nutrition. 2009;90(3):867S-874S. doi:10.3945/ajcn.2009.27462BB.PubMedUsed to support: Explains why blood glutamate and brain glutamate are largely uncoupled. Plasma glutamate runs 50-100 umol/L while brain extracellular fluid is held at 0.5-2 umol/L, because the sodium-dependent glutamate transporters sit exclusively on the abluminal side of the barrier and move glutamate out of brain fluid into the endothelium. The author states this arrangement does not allow net glutamate entry to the brain, and that the barrier is impermeable to glutamate even at high concentrations, apart from a few circumventricular areas with fenestrated capillaries. A review of transport physiology, not a trial of supplementation.
  11. Burrin DG, Stoll B Metabolic fate and function of dietary glutamate in the gut The American Journal of Clinical Nutrition. 2009;90(3):850S-856S. doi:10.3945/ajcn.2009.27462Y.PubMedUsed to support: Reviews evidence that glutamate is a major oxidative fuel for the gut and that dietary glutamate is extensively metabolised on first pass by the intestine, and that it serves as a precursor for glutathione. In infant pigs fed glutamate at four times normal dietary amounts, most of it was either oxidised or converted by the mucosa into other non-essential amino acids. Much of the quantitative work described is in piglets rather than humans.
  12. Boutry C, Matsumoto H, Airinei G, Benamouzig R, Tomé D, Blachier F, Bos C Monosodium glutamate raises antral distension and plasma amino acid after a standard meal in humans. Am J Physiol Gastrointest Liver Physiol. 2011;300(1):G137-45.PubMedUsed to support: Randomised crossover trial in 13 healthy adults who took 2 g of monosodium glutamate or an equivalent sodium chloride control daily for six days before a standard 700 kcal test meal. MSG significantly increased gastric antral distension over the two hours after the meal and raised circulating leucine, isoleucine, valine, lysine, cysteine, alanine, tyrosine and tryptophan compared with the control. Postprandial glucose, insulin, GLP-1 and ghrelin were unchanged, and subjective hunger and fullness were unaffected. A short study of digestive physiology in a small group, not a test of any health outcome.
  13. Shimada A, Baad-Hansen L, Castrillon E, Ghafouri B, Stensson N, Gerdle B, Ernberg M, Cairns B, Svensson P Differential effects of repetitive oral administration of monosodium glutamate on interstitial glutamate concentration and muscle pain sensitivity Nutrition. 2015;31(2):315-323. doi:10.1016/j.nut.2014.07.011.PubMedUsed to support: Randomised, double-blind, placebo-controlled study in 32 healthy adults who drank MSG at 150 mg/kg or salt control in 400 mL of soda on five consecutive days. Baseline glutamate concentrations in jaw muscle, blood and saliva were unchanged, though peak masseter muscle concentration did rise significantly between day 1 and day 5; the authors concluded that interstitial muscle glutamate is not highly disturbed by excessive repetitive MSG intake, and found no robust effect on muscle pain sensitivity. The MSG group did report nausea and headache significantly more often and showed a statistically significant rise in systolic and diastolic blood pressure. A high food-free dose, well above normal dietary exposure.
  14. Dermiki M, Prescott J, Sargent LJ, Willway J, Gosney MA, Methven L Novel flavours paired with glutamate condition increased intake in older adults in the absence of changes in liking. Appetite. 2015;90:108-13.PubMedUsed to support: In 40 adults aged 65 to 88, potato soup carrying a novel flavour (lemongrass or cumin) was eaten three times over six days either with or without a high level of added MSG. After the repeat exposures, participants ate significantly more of the soup whose flavour had been paired with MSG — mean intake rising from 123 g to 164 g (p=0.017) — even though their rated liking of it had not increased. A small single-blind within-subject study using a 5% MSG level far above normal seasoning.
  15. Kouzuki M, Taniguchi M, Suzuki T, Nagano M, Nakamura S, Katsumata Y, Matsumoto H, Urakami K Effect of monosodium L-glutamate (umami substance) on cognitive function in people with dementia European Journal of Clinical Nutrition. 2019;73(2):266-275. doi:10.1038/s41430-018-0349-x.PubMedUsed to support: The one trial giving oral MSG to people with a cognitive endpoint: 159 residents with dementia took 0.9 g of MSG three times daily, or salt control, for 12 weeks. There were no significant differences between groups in total scores on either cognitive instrument used (the Touch Panel-type Dementia Assessment Scale or the Gottfries-Brane-Steen Scale). Reported positives were confined to one TDAS sub-item and to a comparison made after a further four-week period off the supplement. The study was single-blind and one co-author is employed by Ajinomoto, an MSG manufacturer.
  16. Kirkland AE, Baron M, VanMeter JW, Baraniuk JN, Holton KF The low glutamate diet improves cognitive functioning in veterans with Gulf War Illness and resting-state EEG potentially predicts response Nutritional Neuroscience. 2022;25(11):2247-2258. doi:10.1080/1028415X.2021.1954292.PubMedUsed to support: Cognitive functioning improved significantly across every domain tested except memory after one month on a diet that reduces dietary glutamate, though that phase was an uncontrolled before-and-after comparison with no separate control group. In the double-blind placebo-controlled crossover challenge that followed, monosodium glutamate produced significantly variable individual responses; grouping participants after the fact by baseline EEG pattern, 42% fell in a cluster showing cognitive detriment, 24% in a cluster showing benefit and 33% mild or mixed effects. Nothing here indicates that added dietary glutamate aids cognition.