While regulatory agencies consider MSG safe, some studies have questioned its health effects.
Key Facts:
- MSG provides umami taste and enhances palatability as a flavor enhancer
- Animal studies link high dose MSG to cardiotoxicity, hepatotoxicity, neurotoxicity, endocrine and reproductive effects
- Human trials show MSG increases palatability, especially of protein-rich foods, and enhances satiety
- Currently no clear evidence of harm at typical 1-3g dietary MSG doses for most people
- More research needed on impacts of chronic MSG consumption, especially on pain and fetal development
Source: Compr Rev Food Sci Food Saf.
What is MSG & Why is it Used as a Food Additive?
MSG, or monosodium glutamate, is the sodium salt of glutamic acid, an amino acid that provides the savory umami taste.
Glutamate occurs naturally in foods like tomatoes, Parmesan cheese, seaweed, broccoli and meat.
MSG was first identified as the main source of umami flavor in Japanese broths in 1908.
As a food additive, MSG enhances flavor, palatability and satiety.
The FDA recognizes MSG as GRAS or generally recognized as safe.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) and the European Food Safety Authority (EFSA) also consider MSG safe.
In the Western diet, average intake of MSG is estimated to be around 0.3–1.0 g/day.
However, some animal studies using doses far exceeding human consumption have raised concerns about possible toxic effects.
High Dose Animal Studies Linked MSG to Toxicity in Rodents
Animal studies using very high doses of MSG delivered by injection or orally have linked it to:
Cardiotoxicity: Rodent studies using MSG doses from 0.5-8g/kg found oxidative damage, changes in heart rate and rhythm, and increases in enzymes like lactate dehydrogenase that can indicate heart damage. However, doses were hundreds of times higher than human MSG intake.
Hepatotoxicity: Doses of MSG ranging from 0.6-8g/kg given to rodents showed effects like fatty liver, fibrosis, cirrhosis and impaired antioxidant defenses. But again, extremely high doses were used.
Neurotoxicity: Rodent studies using MSG doses from 80mg to 4g per kg reported neuronal damage, changes in neurotransmitters, increased aggression, motor deficits and brain lesions. But the relevance is questionable given the high doses.
Endocrine disruption: Rodents fed very high levels of MSG like 4g/kg as newborns exhibited stunted growth. Another study used an incredibly high 100g/kg MSG dose and caused hyperglycemia.
Reproductive effects: Rat studies using 0.04-0.08g/kg MSG showed ovarian and testicular damage. Pregnant mice given 1-4g/kg MSG bore offspring with altered development. But the doses were thousands of times higher than human MSG intake.
While concerning, these animal studies have major limitations in assessing human MSG safety:
- Doses were extremely high, hundreds to thousands of times higher than human MSG intake of 1-3 grams per day.
- Non-oral routes like injection bypass normal gastrointestinal metabolism and absorption.
- Small samples sizes and lack of adequate controls in some studies.
- Difficult to extrapolate high dose effects in rodents to chronic human MSG consumption.
Human Clinical Trials Found MSG Increases Palatability, Satiety
In contrast to animal studies, human clinical trials using MSG doses in the dietary range have focused on outcomes like food palatability, satiety and intake:
- Adding MSG improved palatability of foods like chicken broth, soups and mashed potatoes. This effect was most notable in protein-rich foods.
- MSG enhanced satiety specifically for protein-containing meals, but not carbohydrate-rich meals.
- Consuming MSG-containing soups increased food intake acutely. However, intake of non-MSG containing foods decreased, suggesting possible compensation.
- High 3-5 gram MSG doses without food caused Chinese restaurant syndrome symptoms like headache, weakness and numbness in sensitive individuals. This is likely a placebo effect.
- Single MSG doses did not alter blood glucose, insulin or appetite-regulating hormones like ghrelin compared to placebo.
Limitations of Human MSG Research:
- Most studies looked at effects of single MSG doses rather than chronic, dietary exposure.
- Small sample sizes with varying study designs and MSG assessment methods.
- Self-reported MSG sensitivity is questionable, with placebo effects likely.
- Lack of high quality human trials on chronic MSG consumption through diet.
No Evidence MSG Consumption is Unsafe in Humans
In summary, animal studies used extremely high, supraphysiological MSG doses that do not reflect human dietary exposure.
High quality clinical trials investigating the chronic effects of typical 1-3 gram daily MSG intake in humans are lacking.
At this point, there is no conclusive evidence that regular MSG consumption is harmful to most individuals at doses consumed in the diet.
However, more human research is needed to better understand the impacts of chronic, long-term MSG intake.
Areas warranting further study include fetal development effects and chronic pain conditions like headaches.
Currently, regulatory agencies consider naturally occurring glutamate and added MSG safe at typical dietary estimated intakes.
But individuals reporting symptoms like headache or flushing after MSG-containing meals may want to limit intake.
References
- Study: A review of the alleged health hazards of monosodium glutamate
- Authors: Anca Zanfirescu et al. (2019)
