Is Monosodium Glutamate Harmful?
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Monosodium Glutamate: Sources and Harmful Effects

Published on Dec 29, 2022   -  5 min read


Monosodium glutamate is considered safe by food safety regulatory authorities, but its long-term safety is still questionable.


Monosodium glutamate, popularly known as MSG, is derived from l- glutamic acid, an essential amino acid. It is commonly used as a preservative, a flavor enhancer having a specific taste as umami. This taste was the chief taste among the people of Asia and developed in western countries later. About a hundred years ago, Kikunae Ikeda recognized this as the fifth basic taste besides salt, sour, sweet, and bitter. The umami taste amplifies flavor intensity and food savoriness.

What Are the Sources of Monosodium Glutamate?

High protein products such as meat, fish, parmesan cheese, Roquefort cheese, and vegetables like tomatoes, mushrooms, broccoli, etc., are rich sources of natural monosodium glutamate. It is also found in many processed foods like salty-flavored snacks, canned vegetables, soups, sauces, and processed meat.

Is Monosodium Glutamate Harmful?

According to the Food and Agriculture Organization (FAO), the World Health Organization (WHO), the US Food and Drug Administration (FDA), and the European Food Safety Association (EFSA), monosodium glutamate is considered to be a substance generally recognized as safe (GRAS). The GRAS - generally recognized as safe status, is given to a food product used before 1958 or when the scientific toxicological reports confirm its safety. But still, some clinical researchers have interrogated the behavior of monosodium glutamate in the human body. This argument arises from the study results that glutamate participates in physiological and pathological processes. Glutamate performs the following physiological functions:

  • The primary source of energy production in enterocytes.

  • As an intermediary component of protein processing.

  • As the progenitor of metabolites like glutathione, N- acetyl glutamate.

  • As an excitatory neurotransmitter in the central nervous system.

Thus, an increase in the levels of glutamate in the central nervous system leads to brain damage, status epilepticus (a seizure that endures longer than five minutes, or retaining more than one attack within a period of five minutes, without coming back to a typical level of consciousness between episodes), cerebral ischemia (a common acute brain injury that occurs due to inadequate blood supply to the brain), traumatic injuries, and chronic neurodegeneration associated with Huntington's chorea (a disease that causes brain nerve damage) .

How Does the Processing of Glutamate Take Place?

In the small intestine, the glutamate undergoes oxidation when administered orally. In the portal blood, a small quantity of glutamate is found, and it originates from the catabolism of glutamine because of intestinal glutaminase activity. There is no absorption of dietary glutamate. This glutamate is further oxidized to get converted into other amino acids. Glutamate is therefore used as a predecessor to synthesize different bioactive compounds.

What Do Preclinical Studies Evaluate Regarding the Effects of Monosodium Glutamate?

Researchers analyze the effects of a single-dose or chronically administered monosodium glutamate on:

  • Biochemical parameters - Total plasma protein, high-density lipoprotein, low-density lipoprotein, triglycerides, glucose, insulin, leptin, oxidative biomarkers.

  • Histological and morphological alterations of organs like the heart, brain, liver, and ovaries.

  • Central nervous system.

Changes in metabolic and neurological activities are seen when 0.04g/kg to 8g/kg of monosodium glutamate is administered either orally, intragastrically, intraperitoneally, or subcutaneously.

What Are the Effects of Monosodium Glutamate on the Cardiovascular System?

Few studies were conducted on different species of rats to assess the relationship between monosodium glutamate and cardiac toxicity.

  1. Laka-UK mice were administered with 4 g/kg of monosodium glutamate subcutaneously for six consecutive days. It was seen that the compound induces dose-dependent oxidative stress in the heart by increasing lipid peroxidation and decreasing superoxide dismutase and catalase activities in the cardiac tissues.

  2. Newborn Wistar rats were administered with 4 g/kg of monosodium glutamate subcutaneously for seven days, and it was seen that there was a rise in total cholesterol, triglycerides, and malondialdehyde levels and decreased high-density lipoprotein cholesterol levels, and glutathione, superoxide dismutase catalase in the cardiac tissues.

  3. Albino rats were administered 4 g/kg of monosodium glutamate intraperitoneally for three consecutive days. The results were histopathological changes as necrotic lesions seen in the cardiac tissues, an increase in total cholesterol, triglycerides, and malondialdehyde levels, and decreased high-density lipoprotein cholesterol levels, and glutathione, superoxide dismutase catalase in the cardiac tissues.

  4. Wistar rats were given a single dose of 0.5 g/kg of the compound, and there was a decrease in the heart rate and bradycardia. Lethal tachyarrhythmia occurred in rats having myocardial infarction when given the dose of 1.5 g/kg.

Thus, it was concluded that the administration of monosodium glutamate enhanced oxidative stress and caused biochemical changes like a rising in lactate dehydrogenase (LDH), aspartate transaminase (AST), and alanine transaminase (ALT). These studies correlate with human health also as the high doses and the routes used for administration can cause cardiac toxicity and arrhythmia.

What Are the Effects of Monosodium Glutamate on Hepatocytes?

Preclinical studies performed on Wistar rats showed that the compound, when mixed with a diet in the dosage of 0.04mg/kg, was administered for forty-two days. The following changes were observed:

  1. Morphological changes like dilated central veins, cytoarchitectural distortions of the hepatocytes, and centrilobular hemorrhagic necrosis (a nonspecific histological conclusion induced by hepatotoxins, congestive hepatic injury, cardiac hepatopathy, and hypoxic injury due to ischaemia).

  2. Biochemical changes such as a rise in the levels of total protein, aspartate transaminase, albumin, and alanine transaminase.

  3. Dose-dependent changes.

Therefore, it was observed that monosodium glutamate administration was associated with increased hepatic lipid peroxidation, decreased catalase, and superoxide catalase activity leading to hepatic toxicity.

What Are the Effects on Central Nervous System Function and Morphology?

Several studies were performed on different species of rats like newborn Wistar rats, strain mice, and albino rats, and dosages of 40 mg/kg and 80 mg/kg of monosodium glutamate were administered through different routes such as oral, subcutaneous, and intraperitoneal. The following alterations were seen.

  1. Neural damage in the cerebral hippocampus and cerebellum.

  2. Increase in plasma glutamate and glutamine levels.

  3. Increase in nitric oxide in the brain tissues.

  4. Decrease in superoxide dismutase and catalase levels.

  5. Induction of neural death.

  6. They decreased locomotor activity due to free radical-induced dopaminergic degeneration.

  7. Altered histology of hippocampus.

What Are the Other Effects?

  1. Tumor development.

  2. Fertility and fetal development are affected.

  3. Suppressed immunity.

  4. Altered musculoskeletal pain sensitivity.

  5. Weight gain and obesity.

What Are the Effects of Monosodium Glutamate on Energy Intake?

Itis contradictory as some clinical studies did not show any prominent differences in hunger ratings or subsequent energy intake. In contrast, some studies showed the same amount of dietary intake of foods irrespective of monosodium glutamate administration.

  • Effect of Monosodium Glutamate in Inducing Headaches and Migraines: Some studies discarded the concept. Oral administration of 75 to 150 mg/kg of the compound increases the frequency of headaches and pericranial muscle tenderness.

  • Effect on Atopic Dermatitis: Food preservatives and monosodium glutamate exaggerate the symptoms of atopic dermatitis in infants and lactating mothers.

  • Monosodium Glutamate Sensitivity: Also known as Chinese restaurant sensitivity, occurs when the compound is administered on an empty stomach. Symptoms such as weakness, flushing, dizziness, numbness, muscle tightness, syncope, headache, and difficulty in breathing are commonly reported.


The article highlights several studies conducted to assess the effects of monosodium glutamate on human health, as it is widely found in food products in the form of preservatives and taste enhancers. Some effects are still questionable and require more research to be done, while some are clear evidence of deterioration caused by this amino acid. Therefore with the data acquired, it is clearly said that monosodium glutamate has adverse effects on human health and is not safe to be eaten in greater quantities and on a regular basis.

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Last reviewed at:
29 Dec 2022  -  5 min read




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