MSG: Understanding the key to Ultimate Umami

Think of the last time you had some fried rice, maybe a stir fry, or a really good bowl of pho. Did you get a headache after or feel a little uncomfortable? Based on what you’ve heard from friends or within the media, you might have attributed the symptoms mentioned above to “Chinese Restaurant Syndrome” due to the presence of MSG in your food, but have you ever considered that these claims may be far from the truth?

Before considering MSG on a molecular and biological level, it is important to understand how it came to be popularized in food preparation. Discovered in 1908 by Japanese scientist, Kikunae Ikeda, MSG or Monosodium Glutamate (C5H8NNaO4) is an organic, odorless and freely soluble compound in water composed of a sodium ion bonded to a glutamate ion [1].

Figure 1: The three forms of glutamate. Although they have slightly different forms, they have the same purpose within the body

Ikeda extracted MSG from seaweed and quickly realized that it was a unique flavor enhancer, bringing out the natural flavors of meats, seafood, salty snacks and stews [1]. Following this discovery,  the fifth flavor, which humans tend to associate with the aforementioned foods, umami, was identified [1]. However, in 1968, Dr. Robert Ho Man Kwok, a Chinese immigrant living in the US, sent a letter to the New England Journal of Medicine [2].          

He outlined a syndrome with symptoms appearing shortly after consuming chinese food at American Chinese restaurants [2]. Symptoms include numbness in the back of the neck, general weakness, palpitation and headaches. Although being widely used in East-Asian cuisine, the belief that MSG causes adverse symptoms rapidly became popularized and the term  “Chinese Restaurant Syndrome” was coined [2]. Despite MSG having been used in many different cuisines throughout North America for at least 20 years prior to these incidents, in 1972, several studies were published in medical journals discussing a direct correlation between the consumption of MSG and the neurological symptoms of Chinese Restaurant Syndrome [2]. Even today, the stigma surrounding the detrimental effects of MSG on health is still highly prevalent despite MSG being composed of sodium and glutamic acid, which are commonly consumed compounds [3].

The amino acid in MSG, glutamic acid, occurs naturally in many foods, including protein-rich meats and cheeses, and is safe for consumption [1]. In fact, according to the FDA, the average American acquires 13 grams of glutamate from food proteins and only 0.55 grams of glutamate from MSG everyday [4]. Not only can glutamate be metabolized by the human body for energy, it is also a primary component in proteins and peptides in the body [5]. Humans naturally produce glutamate —glutamic acid without a hydrogen—within the body, as it is a vital excitatory neurotransmitter aiding in the transmission of action potentials between neurons [5]. In fact, glutamate is the most abundant neurotransmitter in the nervous system and is believed to be involved in cognitive functions such as learning and memory [5]. When consumed, the human body cannot distinguish between the artificially added glutamate within foods and that which is naturally occurring in meats and some vegetables, resulting in both being processed the same way

Figure 2: Examples of food containing glutamate.

[4]. Further analysis demonstrated that glutamate consumption cannot cause brain damage, a popular misconception. Glutamate concentrations are especially low in the extracellular fluid of the brain. This is partially maintained by the blood-brain barrier, a selective barrier that separates the bloodstream and brain tissue, blocking the passage of certain substances. Under normal conditions, glutamate concentrations in the brain are stable with few large fluctuations as the blood-brain barrier is impermeable to a net movement of glutamate into the brain [5]. Shortly after the widespread panic regarding MSG consumption, numerous studies using the double blind placebo-controlled experiments, have repeatedly shown that regular and moderate consumption of MSG has no adverse effects.  Double-blind placebo-controlled studies minimize bias from the researcher or the patient because the subjects and researcher do not know whether it is the substance being tested or if it is a placebo that has been administered. This ensures that the participant’s personal beliefs and the researcher’s expectations will not influence the results, thus preserving the validity of the study. From 1972 to 1980, Dr. Richard Kenney of George Washington University administered high concentrations of MSG to a cohort of over 200 subjects and found that the sensations reported were not reproducible from day to day . Further testing with only 60 subjects was done using various beverages such as coffee, juice and flavored milk, including one beverage containing a 2% MSG solution. Only two subjects had a response to the MSG solution whereas twelve participants responded to the other beverages, demonstrating that the reported symptoms of Chinese Restaurant Syndrome are not unique to the consumption of MSG. Finally, Kenney conducted a double-blind placebo-controlled study in 1986 on individuals who believed they had adverse reactions to MSG. Over a period of four days, the subjects were randomly given two soft drinks containing MSG and two soft drinks that did not. Two of the six subjects reacted to both types of solution while the rest did not react to either showing no correlation between MSG consumption and any adverse reactions [4]. Since then, numerous other studies have been conducted which have all continued to show that MSG is safe for human consumption.

If MSG is safe to consume, why do some individuals feel negative symptoms, such as headaches and irregular heartbeats, after consuming foods that may contain MSG? The real culprit may be an increase in histamine, tyramine or phenylethylamine levels, all of which are amino acids commonly found in cheeses, fermented foods, beans, meats and seafood [6]. Adverse symptoms related to high levels of these amino acids are similar to that of Chinese restaurant syndrome and thus symptoms may have been mistakenly associated with the wrong molecular cause [7].

Along with the weight of numerous biochemical toxicology and medical studies, MSG has been approved by the US FDA since 1958 and is generally recognized as a safe ingredient along with many other common ingredients in the kitchen, such as salt and baking soda [4]. Few ingredients have been questioned as heavily as MSG even though the general consensus among the scientific community is that it is safe for consumption and may even have several benefits in cooking. The greatest benefit is its ability to reduce sodium used in cooking by 30-40% when used in conjunction with salt [4]. MSG contains around one third the sodium found in table salt and can enhance natural flavors better than other seasonings [4]. Therefore, it is ideal for fat or sodium-reduced dishes, allowing chefs to use lighter seasoning without compromising flavor.

Finally, after over forty years of study, there is no evidence to suggest MSG is unsafe for human consumption. In fact, it is a common additive today in many of the everyday processed foods we eat, such as potato chips, and is an essential ingredient in many cultural cuisines. Although stigma against MSG use still exists, next time you browse the grocery store shelves or eat east East-Asian cuisine, you can have more assurance that what you’re consuming is unlikely to harm you.

Written by Angela Yang

Mentored by Milena Cioana

 

References

  1. Appaiah KM. Monosodium Glutamate in Foods and its Biological Effects. Ensuring Global Food Safety. Academic Press; 2010. 217–26.
  2. Germain T. A Racist Little Hat: The MSG Debate and American Culture [Internet].  2017 [cited 2018Dec4]. Available from: https://curj.columbia.edu/article/a-racist-little-hat-the-msg-debate-and-american-culture/
  3. PubChem Compound Database. Glutamic acid [Internet]. 2004 [cited 2018Dec4]. Available from: https://pubchem.ncbi.nlm.nih.gov/compound/L-glutamic_acid#section=Top
  4. International Food Information Council Foundation. Glutamate and Monosodium Glutamate: Examining the Myths [Internet]. 2009 [cited 2018Dec4]. Available from: https://www.foodinsight.org/Content/76/Glutamate-and-Monosodium-Glutamate.pdf.
  5. Hawkins RA, Viña JR. How glutamate is managed by the blood–brain barrier. Biology. 2016;5(4):37. Available from: 10.3390/biology5040037.
  6. Wöber C, Wöber-Bingöl Ç. Triggers of migraine and tension-type headache. Handbook of clinical neurology. 2010;97:161-72). Available from: 10.1016/S0072-9752(10)97012-7.
  7. Chin K, Garriga M, Metcalfe D. The histamine content of oriental foods. Food and Chemical Toxicology. 1989;27(5):283–7. Available from: doi.org/10.1016/0278-6915(89)90129-4.

 

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