Health Benefits Of Glutamic Acid

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Aside from being a protein building block, glutamic acid is physiologically reputed for being the most common excitatory neurotransmitter existing in the human central nervous system and the most vital neurotransmitter at that, playing a major role in the activation of neurons and to a large extent in learning and memory. [1] Glutamic acid is a polar nonessential amino acid with an additional methylene group in its side chain. It can conveniently pass through the blood-brain barrier via a high-affinity transport system to support many brain functions and is involved in energy metabolism upon entering the Krebs cycles and through its conversion to glutamine, which is another amino acid implicated in nitrogen metabolism. [2] The salt or ester of glutamic acid is referred to as glutamate, a non-alien term to those very familiar with the food seasoning monosodium glutamate.

Despite its unarguable importance in neuronal functioning, glutamic acid is considered a nonessential nutrient since the body can naturally synthesize it. A number of foods also are known to be rich in glutamic acid, such as turkey, pork, chicken, lupines, soybeans, egg whites, wheat, and nuts like almonds. [3]

Glutamic Acid And Intelligence

Various ongoing studies have revealed that the function of glutamic acid goes beyond just the generation of excitatory postsynaptic currents. This amino acid also affects neuronal migration, neuronal differentiation, axon genesis, and neuronal survival, which have all spawned interest in glutamic acid regarding its role in memory and other related cognitive functions. Most notably, patients with both acute and chronic brain injuries and several neurodegenerative disorders such as brain ischemia, Parkinson’s disease, and Alzheimer’s disease have been observed to manifest multiple alterations in the glutamate system and its metabolism. Such findings have triggered research on the development of drugs for the recovery of glutamate metabolism system as a potential therapeutic approach for neurodegenerative diseases. [4]

It should be mentioned however that results from earlier studies investigating the effect of glutamic acid on mental retardation are rather contrasting. In the study of Foale (1952), fifteen 10- to 15-year-old boys described as “feeble-minded” and maladjusted and whose intelligence quotients (IQ) ranged from 54 to 76 were treated with glutamic acid for 10 months; eight boys out of the fifteen demonstrated improvement in general adjustment, four of whom achieved an 8- to 11-point increase in IQ. [5] On the other hand, administration of glutamic acid (three daily doses over four months) in sixteen 7- and 15-year-old children with IQ ranging from 42 to 77 was shown to produce no significant effect in the study of Oldfelt (1952). [6]

Glutamic Acid and Blood Pressure

Glutamic acid consumed from one’s diet has been reported to independently lower blood pressure. In the cross-sectional epidemiological study by Stamler et al. (2009), which involved 4,680 40- to 59-year-old individuals from random population samples in China, Japan, the United Kingdom, and the United States, blood pressure was inversely associated with an intake of glutamic acid, to which vegetable proteins have higher levels of than animal proteins do. The researchers also had pointed out that people who consumed principally vegetable protein compared with animal protein and therefore had higher intake of glutamic acid and, to a lesser extent, other amino acids studied (including cystine, proline, phenylalanine, and serine) have lower blood pressure. [7]

Glutamic Acid and Cancer

Glutamic acid’s importance in the treatment against cancer lies on its being a source of endogenous derivatives with established anticancer properties, particularly glutamine and glutamate. For instance, L-glutamic acid-γ-(4-hydroxyanilide) isolated from the mushroom Agaricus bisporous has been reported to inhibit B16 melanoma cells in culture, and synthetic amides of L-glutamic acid appear to exhibit anticancer activity against Ehrlich ascites carcinoma. Glutamic acid can also act as a promising conjugate to other anticancer agents because of its ability to increase efficacy of anticancer drugs and decrease these drugs’ toxicity on normal cells. All-trans retinoic acid, an active metabolite of vitamin A used as part of the therapy against acute promyelocytic leukemia and myelodysplastic syndrome, is often paired with glutamic acid or its sodium salts to achieve better solubility, transportation, and bioavailability. Furthermore, paclitaxel, a well-known chemotherapy drug for ovarian, breast, and non-small cell lung cancers, is conjugated with water-soluble polyglutamate, which according to studies results in more antitumor activity than free paclitaxel alone. [8]