“A half-truth is the most cowardly of lies.” – Mark Twain
Story so far
Monosodium glutamate or MSG or Aginomoto is a very commonly used food additive that makes our Pringles® so irresistible, our Chinese food so delicious and our parmesan so savoury. This indescribable taste is called “umami” or the 5th basic taste sense.1 By labeling MSG as a new taste in itself, the food industry has legitimized its use despite the toxicity concerns that emerged in the 1900s. The manufacture of MSG was patented in 1908 by the Aginomoto Company in Japan.2 In the 1960s, concerns were raised regarding the toxicity of MSG in light of various animal studies in the past. In response to these allegations, the International Glutamate Technical Committee (IGTC) was formed to represent the interests of glutamate industry. Soon after, many organizations emerged in different parts of the world to support the glutamate trade. Thus began an era of lies, deceit, wrongful research methodologies and blatant denials to keep afloat this multi-billion dollar industry.
MSG is a sodium salt of glutamic acid (GA).
GA is a non-essential because it can be synthesized in the body from other substrates.
Interestingly, natural glutamate (from fruits, vegetables and meat) is a Levo-isomer and is bound to other proteins and peptides in food. Bound glutamate is slowly released during digestion and absorbed according the body’s requirements.3 Synthetic Glutamates, like MSG, are free (unbound) and are usually a mixture of D and L isomers, pyroglutamic acid and other contaminants, depending on the manufacturing process. Though our bodies are capable of metabolizing the
L-glutamic acid, the D-isomer is known to cause neuronal toxicity.
Half truth 1: A Cochrane review reports no link between MSG and Asthma
This Cochrane review is limited to only 2 cross-over studies which demonstrated no link between MSG and asthma, while largely excluding other study designs that report such a link.4
A challenge study with MSG in subjects with asthma concluded that there is a dose dependent asthmatic reaction. In one group the asthmatic reaction was delayed up to 12 hours making causal-link highly difficult for the patients and the treating physicians.5
Although MSG does not induce asthma in non-asthmatic people,6 it definitely acts as a trigger for asthmatic ones.7
Half truth 2: Reviews show that MSG is not “statistically” associated with adverse reactions.
Statistical significance is inherently very deceptive unless one delves deep into the specifics. In the literature, “Chinese restaurant syndrome” or CRS is the term referred to a constellation of symptoms that happen after consumption of Chinese food.2 Subsequently, MSG was recognized as the culprit. However, these symptoms are not consistent in occurrence in a set population. In-effect, for some it triggers asthma, some show numbness, tingling and nervous reactions, while the rest may show neuro-excitatory effects leading to migraines etc. While some reactions are included in these studies, some other reactions like arrhythmia, tachycardia, depression and anxiety attacks are largely ignored as end-points.2
Another major decisive factor in placebo-controlled studies is the placebo itself. In many earlier studies, aspartamine, carrageenan, gelatin or other enzymes were used as placebos which had similar effect to free glutamine. Thus, statistical difference between test and control groups can be eliminated.2
A multi-center, double blind, place-controlled, multiple challenge evaluation study at Harvard tested the effect of MSG after 8 hours of fasting in 130 participants.8 The responses were reported as being inconsistent. But if you dig deeper into the study the following facts are revealed:
Only 10 symptoms were mentioned on the questionnaire.
In the first round, the MSG group reported significantly higher symptoms than the placebo group. Not just that, symptoms other than those 10, was also significantly higher in MSG group.
In the subsequent challenges, the statistical significance disappeared and this could be attributed to various reasons. Firstly, the number of participants in each challenge progressively decreased with only 12 participants in the last one. This in itself reduces the statistical credibility. Secondly, since the mechanism of toxicity of MSG is still under debate, there is possibility that an individual had different set of symptoms at each challenge. Thus, though this study seems to be decisive, it still has many open questions regarding the expression of toxicity of MSG.
Half truth 3: Lack of data means MSG is safe.
There is a dearth of data when it comes to associating MSG with headaches, migraines, neuro-muscular pains etc.
MSG interferes with acetylcholine receptors in the brain triggering migraine attacks. This assertion needs clinical evidence but that doesn’t keep MSG in the clear because in-vitro results are convincing.9
Another study demonstrated that vitamin B6 reduces MSG induced symptoms which also indicates that MSG does induce some neuronal aberrations which are corrected by vitamin B6 supplementation.10
Half truth 4: MSG has been deemed safe in animal studies
A study on mouse cortical neurons has shown that there is dose-dependent swelling and death of mature neurons with MSG. The toxicity doesn’t reduce with boiling but reduces with addition of vitamin C (probably because of anti-oxidant effect).11
A study on effects of isomers of Glutamic acid on chicks concluded that, they tolerated 15% of L-isomer without growth retardation where as 3.75% of the D-isomer was enough to elicit severe growth retardation which could not be reversed using additional vitamin or amino acid supplements.12
In fact, studies as early as 1969 have reported brain lesions in lab animals exposed to MSG.13 This study was subsequently also replicated by many neuroscientists.2
Half truth 5: Glutamate from natural foods is same as the food additive
Toxicology studies have shown that the plasma GA concentration peaks higher when MSG is administered directly rather than if it is offered as a mixture of other proteins and peptides.14
Also, as previously mentioned, food additives are D-isomers as compared to the natural form which is the L-isomer.
Natural glutamate is bound to proteins in the food and is absorbed in the intestine and later metabolized in the liver (first pass metabolism).Free glutamate is absorbed directly in the stomach increasing the plasma free glutamine levels. Increased free glutamine levels have been associated with Parkinson’s disease, growth retardation and brain inflammation. This is especially important in children because the blood-brain-barrier is not tight enough to prevent the free glutamine from reaching the neurons.15
So….Is MSG safe to consume?
There is dearth of unbiased research to associated MSG with Chinese syndrome. However, available animal studies, in-vitro testing and limited in-vivo studies have shown some alarming results. What is even more alarming is the fact that without proper safety data, MSG in its various forms is used liberally in processed food. Our body can process small amounts of toxins but the cumulative effect of eating it every day could be potentially detrimental to our health.
Today’s verdict: Avoid obvious MSG intake because you might be eating some anyway!
The following is a list of foods containing MSG (or its end product free glutamate). These are sources for free glutamate which cause a sudden spike in blood glutamine levels as opposed to bound glutamate which is metabolized efficiently by the body.16
Taco Bell® – seasoned meat – contains autolyzed yeast – which contains free glutamate
Other menu items that contain soy sauce, natural flavors, autolyzed yeast or hydrolyzed protein which can contain up to 20% free glutamic acid – the active part of MSG.
Hamburger Helper Microwave Singles® (targeted towards children)
Campbell’s® soups – all of them – based on their commitment to add “umami” (read – MSG) to their products
Pringles® (the flavored varieties)
Boar’s Head® cold cuts and most of their hotdogs
Progresso® Soups – all of them
Lipton® Noodles and Sauce
Lipton® Instant soup mix
Unilever or Knorr® products – often used in homemade Veggie dips.
Kraft® products nearly all contain some free glutamate
Cup-a-soup® or Cup-o-Noodles®
Planters® salted nuts – most of them
Accent® -this is nearly pure MSG
Braggs® Liquid Aminos – sold at Whole Foods
Hodgson Mill Kentucky Kernel Seasoned Flour®
Tangle extract (seaweed extract) – found in sushi rolls (even at Whole Foods) Seaweed is what MSG was first isolated from.
Fish extract – made from decomposed fish protein – used now in Japanese sushi dishes – very high in free glutamate.
sausages – most supermarkets add MSG to theirs
processed cheese spread
supermarket poultry or turkeys that are injected or “self-basting”
restaurant gravy from food service cans
flavored ramen noodles
boullion – any kind
instant soup mixes
many salad dressings
most salty, powdered dry food mixes – read labels
flavored potato chips
restaurant soups made from food service soup base or with added MSG
hydrolyzed vegetable protein (found in many processed AMERICAN foods, like canned tuna and even hot dogs)
hydrolyzed plant protein (found in many processed AMERICAN foods, like canned tuna and even hot dogs)
autolyzed yeast (found in many processed AMERICAN foods, read labels)
beet juice – it is used as a coloring, but MSG is manufactured from beets and the extract may contain free glutamic acid – Yo Baby – organic baby yogurt has just changed the formula to include beet extract
yeast food or nutrient
soy protein isolate
dry milk and whey powder
“natural flavors” – may contain up to 20% MSG
malted barley flour – found in many supermarket breads and all-purpose flours including: King Arthur, Heckers, and Gold Medal flour
body builder drink powders containing protein
Parmesan cheese – naturally high in free glutamate
over-ripe tomatoes – naturally high in free glutamate
mushrooms – naturally high in free glutamate
Medications in gelcaps – contain free glutamic acid in the gelatin
Cosmetics and shampoos – some now contain glutamic acid
Fresh produce sprayed with Auxigro in the field. (Yes the EPA approved this. It appalled us too.)
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2 Samuels A. The toxicity/ safety of processed free glutamic acid (MSG): A study in suppression of information, accountability in research. Policies and Quality Assurance (1999); 6: 259-310.
4 Zhou Y et al. Monosodium glutamate avoidance for chronic asthma in adults and children. Cochrane Database Systematic Review (2012); 6: CD004357.
5 Allen DH et al. Monosodium L-glutamate-induced asthma. Journal of Allergy and Clinical Immunology (1987). 80: 530-537.
6 Shi Z et al. Monosodium glutamate intake, dietary patterns and asthma in Chinese adults. PLoS One (2012); 7: e51567.
7 Moneret-Vautrin DA. Monosodium glutamate-induced asthma: study of the potential risk of 30 asthmatics and review of the literature. Allergy and Immunology (Paris) (1987); 19: 29-35.
8 Geha RS et al. Multicenter, double-blind, placebocontrolled, multiple-challenge evaluation of reported reactions to monosodium glutamate. Journal of Allergy and Clinical Immunology (2000); 106: 973-980.
9 Leira, R., & Rodrı´guez, R. (1995). Dieta y migrana. Revista de Neurologıa, 24, 534–538.
10 Folkers K et al. The biochemistry of vitamin B6 is basic to the cause of the Chinese restaurant syndrome. Hoppe Seylers Z Physiol Chem (1984); 365: 405-414.
11 Xiong JS. Deciphering the MSG controversy. Int J Clin Exp Med. (2009); 2: 329–336.
12 Maruyama K et al. Effects of D-, DL-and L-glutamic acid on chicks. Journal of Nutrition (1975); 105: 1012-10019.
13 Olney JW. Brain lesions, obesity, and other disturbances in mice treated with monosodium glutamate. Science (1969); 164: 719-721.
14 Marrs TC et al. The absorption by human volunteers of glutamic acid from monosodium glutamate and from a partial enzymic hydrolysate of casein. Toxicology (1978); 11: 101-107.
15 Douglas GB & Stoll B. Metabolic fate and function of dietary glutamate in the gut. The American Journal of Clinical Nutrition (2009); 90(suppl): 850S-856S.