Is MSG Bad for You?
Unpacking the science behind monosodium glutamate: safety, myths, and what research really says about this common flavor enhancer.
Monosodium glutamate (MSG) is a widely used food additive that enhances the savory umami flavor in dishes like soups, snacks, and processed foods. Despite its prevalence, MSG has been controversial since the 1960s, with claims linking it to headaches, obesity, and other health issues. Regulatory bodies like the U.S. Food and Drug Administration (FDA) classify MSG as “generally recognized as safe” (GRAS) when consumed in typical amounts. However, some individuals report short-term symptoms, prompting ongoing research into sensitivities and long-term effects.
What Is MSG?
MSG, or monosodium glutamate, is the sodium salt of glutamic acid, a naturally occurring non-essential amino acid found in foods like tomatoes, cheese, mushrooms, and meat. It was first isolated in 1908 by Japanese chemist Kikunae Ikeda from kombu seaweed, leading to its commercial production as a flavor enhancer.
Commercially, MSG is manufactured through bacterial fermentation of starches or sugars, similar to yogurt or beer production. This process yields a white, crystalline powder that’s about 78% glutamate and 12% sodium, with the rest water. Unlike table salt, MSG directly stimulates taste receptors for umami, making foods taste richer without adding sweetness, sourness, or bitterness.
Humans consume glutamate naturally—around 13 grams daily from protein-rich foods—while added MSG contributes just 0.5-1 gram on average in Western diets. In Asian cuisines, intake can reach 3-5 grams daily without widespread harm.
How Does MSG Work in the Body?
Upon ingestion, MSG dissociates into sodium and glutamate in the digestive tract. Free glutamate is absorbed efficiently, providing energy to gut cells or serving as a precursor for proteins and neurotransmitters. In the brain, glutamate acts as the primary excitatory neurotransmitter, but a blood-brain barrier prevents dietary MSG from directly affecting it under normal conditions.
MSG boosts salivation and enhances food palatability, potentially influencing appetite. Studies show it can alter carbohydrate metabolism and satiety signals, varying by meal composition. For instance, a 2g MSG-supplemented meal increased post-ingestion amino acid levels like leucine and tryptophan.
History of MSG Controversy
The “MSG scare” began in 1968 when a letter to the New England Journal of Medicine described “Chinese Restaurant Syndrome” (CRS)—symptoms like numbness and palpitations after eating MSG-laden food. This was followed by neurotoxicology studies by John Olney, who injected mice with massive MSG doses (equivalent to humans eating pounds at once), causing brain lesions.
Critics highlighted methodological flaws: doses far exceeded human exposure (0.01 mg/g body weight daily vs. Olney’s 7 mg/g), no blinding, and no relevance to oral intake. Follow-up human studies in the 1970s-1990s, including double-blind trials, found no consistent symptoms at realistic doses. East Asian populations consume far more MSG without epidemics of issues, debunking broad toxicity claims.
Is MSG Safe? What the Science Says
Decades of research affirm MSG’s safety for most people. The FDA’s GRAS status is backed by Joint FAO/WHO Expert Committee on Food Additives (JECFA) and European Food Safety Authority (EFSA), setting an acceptable daily intake of “not specified”—indicating no safety concerns at typical levels.
- Preclinical concerns: Animal studies report toxicity at extreme doses, like cardiotoxicity or neurotoxicity, but methodological flaws (e.g., subcutaneous injection, mega-doses >25x human intake) limit human relevance.
- Human trials: No links to tumorigenesis, genotoxicity, or immune suppression at dietary levels. Oral MSG (up to 150 mg/kg) shows minimal effects on nociception or metabolism.
- Long-term data: Population studies in high-MSG regions show no elevated disease rates.
That said, vulnerable groups like infants may warrant caution due to immature blood-brain barriers, though evidence is inconclusive.
MSG Symptom Complex (Chinese Restaurant Syndrome)
MSG symptom complex includes headache, flushing, palpitations, nausea, and tingling, typically after large doses (>3g) on an empty stomach. Double-blind trials show 1-2% of people react mildly, but symptoms are short-lived (hours) and not allergic.
A review of trials found reactions more likely with pure MSG capsules than in food, suggesting context matters. No long-term harm occurs, and many “sensitive” individuals react inconsistently. Mayo Clinic advises avoidance if symptoms occur, but population-wide risk is negligible.
Does MSG Cause Obesity or Metabolic Issues?
Claims link MSG to overeating due to enhanced flavor or leptin resistance. Mixed evidence: one study of 10,000+ people suggested higher intake correlated with overweight risk, but a 1,282-person trial found no effect.
Animal mega-dose studies show hyperinsulinemia and weight gain, but irrelevant to humans (e.g., 100g/kg diet). Enhanced palatability may increase intake short-term, but no causal obesity proof exists. Moderation in processed foods is key, not MSG per se.
Other Potential Health Effects
| Claim | Evidence Summary | Source |
|---|---|---|
| Asthma | 1987 small study suggested provocation; 2012 larger review found no link. Limited child data. | |
| Pain Sensitivity | High-dose rodent studies show muscle sensitization; human oral doses up to 300 mg/kg mildly reduce threshold. | |
| Neurotoxicity | Only at injection mega-doses; oral intake safe due to barriers. | |
| Cancer/Genotoxicity | Cell studies at 250-8000 μg/ml show aberrations; irrelevant to diet (<1g/day). |
Immune effects like thymocyte apoptosis occur at supra-physiological doses. Overall, no robust human evidence for harm.
What Foods Contain MSG?
- Natural sources: Parmesan cheese, soy sauce, tomatoes, peas, mushrooms.
- Added MSG: Instant ramen, chips, canned soups, fast food, salad dressings.
- Hidden forms: Hydrolyzed proteins, yeast extracts, “natural flavors”—must be labeled if pure MSG.
Average U.S. intake: 500mg/day; check labels for avoidance.
Should You Avoid MSG?
For most, no—MSG is safe and useful for low-sodium flavoring. If you suspect sensitivity, opt for whole foods or MSG-free products. Those with migraines or asthma might test elimination. Balance is key: limit ultra-processed foods regardless.
Frequently Asked Questions (FAQs)
What is MSG made from?
MSG is produced via fermentation of starches by bacteria, yielding pure glutamic acid sodium salt. It’s chemically identical to natural glutamate.
Does MSG cause headaches?
Some report headaches from high doses, but double-blind studies show no consistent link for most. Symptoms resolve quickly.
Is MSG natural?
Glutamate is natural; commercial MSG is synthesized but matches food-derived forms. It’s vegan and kosher.
Can MSG cause obesity?
No strong evidence; palatability may boost intake, but studies are mixed and confounded by diet quality.
Is MSG banned anywhere?
No major bans; FDA requires labeling. Some restaurants voluntarily avoid it.
How much MSG is safe per day?
JECFA says “not specified,” meaning no upper limit needed for safety.
References
- A review of the alleged health hazards of monosodium glutamate — PMC (NIH). 2019-11-13. https://pmc.ncbi.nlm.nih.gov/articles/PMC6952072/
- Find Out Whether MSG Is Good or Bad for You — AARP. 2023-08-15. https://www.aarp.org/health/healthy-living/msg-health/
- MSG: All You Need To Know — ZOE. 2024-02-20. https://zoe.com/learn/msg
- Monosodium glutamate (MSG): Is it harmful? — Mayo Clinic. 2023-05-10. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/monosodium-glutamate/faq-20058196
- The Rotten Science Behind the MSG Scare — Science History Institute. 2022-06-01. https://www.sciencehistory.org/stories/magazine/the-rotten-science-behind-the-msg-scare/
- What is MSG and How is it Made? — Ajinomoto. 2023-11-05. https://www.ajinomoto.com/msg/what-is-msg-and-how-is-it-made
Similar Articles
Read full bio of Sneha Tete
