Monosodium glutamate, commonly known as MSG, is a sodium salt derived from glutamic acid—an amino acid naturally present in many foods and the human body. Widely used as a flavor enhancer, MSG imparts the umami taste, a savory flavor distinct from sweet, salty, sour, or bitter.
With over 100 years of culinary history, MSG has found its way into countless processed foods worldwide and is especially popular in developing and sugar-producing countries. While its use is ubiquitous, MSG has garnered both acclaim and controversy over the years.
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Safety and regulatory status of MSG
The safety of MSG has been extensively evaluated by regulatory bodies globally. In the United States, the Food and Drug Administration (FDA) has designated MSG as “Generally Recognized as Safe” (GRAS). Similarly, international organizations, including the Joint Expert Committee on Food Additives (JECFA) of the United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO), have classified MSG in the safest category for food additives.
Research confirms that the body processes added MSG in the same way as naturally occurring glutamate found in foods like cheese and tomatoes. The FDA has also affirmed that MSG is safe when consumed at customary levels, with an Acceptable Daily Intake (ADI) set at 30 mg/kg of body weight.
Metabolism of MSG
The human body metabolizes glutamate—both natural and added—efficiently. In fact, the digestive system produces glutamate during protein breakdown. Even infants as young as one year old metabolize glutamate as effectively as adults, with breastfed newborns consuming higher concentrations of free glutamate than any other stage of life. When MSG is consumed with metabolizable carbohydrates, peak plasma glutamate levels are notably reduced, showcasing the body’s adaptability to process it.
MSG and “Chinese Restaurant Syndrome” (CRS)
The term “Chinese Restaurant Syndrome” (CRS) arose in the 1960s, following anecdotal reports of symptoms like muscle tightness, flushing, and headaches after eating Chinese food. Early suspicions linked these symptoms to MSG, but subsequent clinical studies have been inconclusive. Controlled trials reveal that only large doses of MSG—over 3 grams consumed on an empty stomach—may cause mild symptoms in sensitive individuals. Notably, such symptoms are rare and inconsistent when MSG is consumed with food, as is typical in a normal diet.
Critics argue that CRS is more a cultural construct rooted in bias rather than scientific evidence. The lack of reproducible findings and the absence of symptoms in typical dietary contexts further weaken claims associating MSG with CRS.
MSG and headaches
MSG’s potential link to headaches has also been studied extensively. Some research indicates that consuming MSG in high concentrations, particularly in beverages or soups exceeding 2% MSG content, may trigger headaches. However, these studies often lacked proper blinding, as MSG’s distinctive taste made it identifiable. When MSG is consumed with food, its association with headaches diminishes significantly. Studies using moderate doses (1.5 to 3 grams) have generally found no meaningful impact on headache frequency.
MSG and weight gain/obesity
The relationship between MSG consumption and obesity remains a topic of debate. Some studies suggest a positive correlation, with higher MSG intake linked to increased body mass index (BMI) and metabolic syndrome prevalence. For example, a study of over 10,000 Chinese adults reported an association between MSG consumption and higher BMI.
Conversely, other research found no significant link between MSG intake and weight gain after adjusting for lifestyle and dietary factors. Variability in study methodologies—such as differing approaches to estimating MSG consumption—may account for these mixed findings. Notably, when total glutamate intake was considered, an inverse association with weight gain was observed, though this correlation disappeared after further adjustments.
MSG and other health concerns
Asthma and Rhinitis: Early studies linking MSG to asthma exacerbation were flawed, often involving small sample sizes or participants withholding medication. Larger studies, including one involving Chinese adults, found no association between MSG intake and asthma. Similarly, while some reports suggest a link between MSG and rhinitis symptoms, reliable clinical evidence is lacking.
Pain: High doses of MSG (2.5-5 grams) have been associated with increased headaches and muscle tenderness in some studies. For example, patients with myofascial temporomandibular disorder (TMD) reported more intense pain following MSG consumption.
Reproductive health and fetal development: Animal studies have suggested that high doses of MSG may impact reproductive health and fetal development. Male rats exhibited reversible sperm abnormalities, while female rats showed changes in ovarian and uterine structures. MSG has also been shown to cross the placenta in pregnant animals, potentially affecting fetal neurodevelopment. However, these findings stem from doses far exceeding typical human dietary exposure, highlighting the need for further research.
MSG and Neurotoxicity
High-dose animal studies have raised concerns about MSG’s neurotoxic potential. Preclinical findings link excessive MSG exposure to brain lesions, cognitive impairment, and increased beta-amyloid levels in rodent models. Importantly, these studies often used injection methods or dosages that do not reflect normal dietary consumption, limiting their relevance to humans.
The Umami taste and MSG
The umami flavor profile provided by MSG not only enhances the savory quality of foods but also offers potential clinical benefits. Umami stimulation increases salivary secretion, which could aid elderly individuals experiencing dry mouth. Interestingly, umami perception may also interact with sweet taste receptors, potentially opening avenues for culinary and therapeutic innovations.
Production and sustainability
Initially produced through hydrolysis of vegetable proteins, MSG production evolved to include direct chemical synthesis and fermentation. Today, fermentation—introduced in 1956—is the predominant method, yielding a more cost-effective and environmentally friendly process. The global annual production of MSG is approximately 2 million tonnes, with the sugar industry exploring its potential as a diversification opportunity.
Mitigating the effects of MSG
Some research suggests that vitamins A, C, D, and E, as well as compounds like quercetin and curcumin, may mitigate certain adverse effects of MSG. For example, curcumin has shown promise in alleviating cognitive impairments associated with high MSG intake in animal studies.
What our expert in the subject matter thinks
Despite decades of controversy, regulatory bodies worldwide agree that MSG is safe when consumed within normal dietary levels. Many reported adverse effects stem from studies using excessive doses or experimental conditions that do not reflect typical human consumption. While ongoing research is warranted, particularly concerning pain and fetal development, the evidence largely supports MSG’s safety as a flavor enhancer. Understanding the science behind MSG can help dispel myths and foster a more nuanced perspective on this widely used food additive.
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