Fact check: MSG doesn’t cause neurological disorders, is overall safe for human consumption

The claim: MSG is a deadly brain toxin, causes neurological disorders and other health problems

While the COVID-19 pandemic may have forced many Americans across the nation indoors, it has also encouraged them to expand their palates with adventurous spices, natural ingredients, meal kits and home cooking, food industry experts say. 

But one ingredient to watch out for, claims one social media post, is MSG, or monosodium glutamate. 

“Deadly Brain Toxin,” reads a graphic shared in a Jan. 26, 2019, Facebook post which has recently gotten attention online. “MSG causes serious neurological disorders and other physiological health problems.”

It then lists a litany of other health problems such as headache, infantile obesity, numbness, heart palpitations and weakness. 

To emphasize its claim, the post also includes an image of Ac’cent seasoning – the main ingredient of which is MSG – photoshopped with the skull and crossbones hazard symbol.  

USA TODAY has reached out to the poster for comment.

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MSG is a common flavor enhancer and preservative that has been in global use for the last 100 years. Its unsavory reputation has been largely based on flawed scientific studies in animals and humans, which have been debunked by more recent research.

What is MSG?

First discovered by Japanese biochemist Kikunae Ikeda, MSG is made up of sodium and glutamate, one of the most abundant amino acids found within the human body and nature. Glutamate plays a critical role in neuromuscular development, metabolism and many other vital biological functions. 

MSG by itself doesn’t have much flavor, but when it’s added into certain foods, it stimulates and heightens taste buds on our tongues that sense umami, a Japanese portmanteau meaning a pleasant, savory taste.  

When Ikeda first happened on MSG in 1907, he had distilled it from a glutamate-rich seaweed broth used extensively in Japanese cuisine. Today, MSG is made by fermenting starch, corn, wheat, beets or other sugar-rich foods with bacteria that eat the sugar and spit out proteins abundant in glutamic acid, an alternative form of glutamate. (Foods like yogurt, kimchi and sauerkraut are also made via fermentation.) 

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Humans have been eating glutamate-rich foods, like tomatoes and cheese, for centuries. MSG has long been associated with Chinese cooking, but it’s also used to flavor Caribbean and Latin American sauces, Doritos, sandwiches at Chick-fil-A, low sodium products and many other processed foods, Dr. Stephen Prescott, president of the Oklahoma Medical Research Foundation, wrote in The Oklahoman.

Flawed studies, no real scientific evidence 

Health concerns over MSG arose in 1968 after a Chinese-American doctor wrote a letter to the New England Journal of Medicine wondering if the flavor enhancer was the cause for his heart palpitations, numbness and weakness felt whenever eating at a Chinese restaurant. 

The letter, published under the title “Chinese-Restuarant Syndrome,” spawned a flurry of animal and human studies where subjects were given MSG either through an injection or orally. One 1969 study by Washington University researcher Dr. John Olney found injecting significantly large doses under the skin of newborn mice lead to impaired brain development, stunted growth, obesity and infertility in female mice. Olney repeated the same experiment, this time giving MSG orally to rhesus monkeys, and came to a similar finding. 

However later, in 19 other monkey studies conducted by other researchers, no one observed results anything like Olney’s. 

In one human study where 71 healthy individuals were given either MSG or a placebo, both groups complained of symptoms like headaches or numbness roughly at the same rate, even when participants were swapped over to the alternative option. 

In the years following, many organizations, including the U.S. Food and Drug Administration, the National Academy of Sciences, the World Health Organization and the American Medical Association, all deemed MSG safe to eat. 

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In 1992, the FDA launched a formal review of MSG’s supposed ill effects, and in 1995 it concluded it was overall safe although it may cause mild, short-term reactions like headaches, numbness and palpitations in only a tiny part of the population. The report noted these symptoms tended to occur in individuals who ate more than 3 grams of MSG without food. It’s important to bear in mind, the typical serving of food with MSG added is less than 0.5 grams. Consuming six times this amount without food at one time is unlikely, the FDA said on its MSG question and answer website. 

A 2009 study found dietary glutamate does not cross the blood-brain barrier – a system of blood vessels that regulates what goes in and out of the brain and spinal cord – in large amounts and so is unlikely to affect brain function.

A 2020 review of studies involving MSG also found many of its reported negative health effects “have little relevance for chronic human exposure and are poorly informative as they are based on excessive dosing that does not meet with levels normally consumed in food products.”  

The impact of MSG on weight has been less clear cut, with some studies suggesting it can cause weight gain but others observing there is no connection between the two.

Our rating: False

We rate the claim that MSG is a deadly brain toxin that causes neurological disorders and other health problems FALSE, based on our research. MSG is a naturally occurring food substance that has been used for over 100 years. Claims that it can be dangerous to human health are based on flawed scientific studies which have been debunked by more recent research. A small population of people may be sensitive to MSG, but the effects are short-term and not life-threatening.  

Our fact-check sources:

  • Fortune, May 25, A necessity during lockdown, meal kits will outlive COVID. Here’s why 
  • CNBC, Dec. 29, 2020, The pandemic’s new chefs and foodies: How the health crisis shaped what we cook and crave
  • Ac’cent, accessed June 24, Ac’cent Flavor Enhancer  
  • The University of Tokyo School of Medicine, accessed June 24, Kikunae Ikeda (“Discoverer of “Umami”)
  • University of Rochester Medical Center, accessed June 24, Health Encyclopedia – Glutamid Acid 
  • WNYC Studios, Aug. 18, 2020, Umami: A Century Of Disbelief 
  • U.S. Food and Drug Administration, Nov. 19, 2012, Questions and Answers on Monosodium glutamate (MSG)
  • Oklahoma Medical Research Foundation, accessed June 24, Dr. Stephen M. Prescott profile 
  • The Oklahoman, March 23, Bodywork: Should you avoid MSG in foods? 
  • New England Journal of Medicine, April 4, 1968, Chinese-Restaurant Syndrome 
  • Science, May 9, 1969, Brain Lesions, Obesity, and Other Disturbances in Mice Treated with Monosodium Glutamate 
  • The Journal of Nutrition, April 1, 2000, The Safety Evaluation of Monosodium Glutamate 
  • Food and Chemical Toxicology, March 23, 1993, Monosodium L-GLUTAMATE: A double-blind study and review 
  • GoodRx, June 23, Health Debunked: Is MSG Really Bad for You? 
  • U.S. Food and Drug Administration, July 1995, Analysis of Adverse Reactions to Monosodium Glutamate (MSG)
  • American Journal of Clinical Nutrition, July 1, 2009, The blood-brain barrier and glutamate
  • Cold Spring Harbour Perspectives in Biology, Jan. 5, 2015, The Blood-Brain Barrier
  • Comprehensive Reviews in Food Science and Food Safety, Jan. 9, 2020, A review of the alleged health hazards of monosodium glutamate
  • The American Journal of Clinical Nutrition, March 17, 2011, Consumption of monosodium glutamate in relation to incidence of overweight in Chinese adults: China Health and Nutrition Survey (CHNS)
  • Public Health Nutrition, Aug. 16, 2012, Monosodium glutamate is not associated with overweight in Vietnamese adults 

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