The Safety of MSG
I’ve had many questions about MSG over the years and so I have put this article together examining its safety.
Monosodium glutamate (MSG) is the salt of the amino acid, glutamic acid. The salt is the crystalline (not dissolved in water) form of glutamic acid. Salts of acids often end in “-ate.” Glutamic acid is a non-essential amino acid, which means our bodies can normally make all we need of it.
Although the name is very similar, glutamic acid should not be confused with glutamine, which is another nonessential amino acid that can become conditionally essential in trauma. Supplements of glutamine are used in injury healing and also promoted to bodybuilders.
The sodium portion of MSG is not the important component because as soon as MSG becomes dissolved in the aqueous medium of the body, the sodium molecule separates from the glutamate. Most glutamate that humans ingest is in the form of protein, which then gets broken down into free glutamate in the digestive tract. Beyreuther et al. report that Europeans ingest about 1 g of free glutamate on average (not including additives like MSG):
In addition to bound GLU [glutamate], some products like fresh fruits, vegetables and cheese contain various amounts of free GLU (unprocessed potatoes: 50–80 mg/100 g, tomatoes: 200– 300 mg/100 g, tomato products: up to 630 mg/100 g, long matured cheese like Parmesan: up to 1200 mg/100 g). Based on a mixed diet, intake of free GLU can be presently estimated to 1 g/day. (1)
Considering the above information, people are basically eating glutamate on a daily basis, and cannot realistically avoid doing so.
MSG has been thought to produce a reaction in some people who are sensitive to it. The reaction can include burning, tingling, numbness, facial pressure or tightness, chest pain, headaches, nausea, palpitations, asthma reactions, drowsiness, weakness, and allergic reactions.
In 2009, A.M. Williams and K.M. Woessner wrote a review on MSG (2). Willams and Woessner are with the Division of Allergy, Asthma, and Immunology at Scripps Clinic in San Diego, CA. Scripps is a nonprofit, community-based health care delivery network. I point this out because it would seem unlikely that they would be influenced by MSG manufacturers; additionally, neither researcher is listed as having industry ties at the Integrity in Science Database.
According to Williams and Woessner, hydrolyzed vegetable protein, hydrolyzed plant protein, hydrolyzed soy protein, and autolysed yeast extract are other sources of free glutamate. They also say that the majority (up to 95%) of dietary glutamate is used as energy by intestinal cells.
Williams and Woessner reviewed the studies looking at MSG and MSG Symptom Complex, which includes burning sensations, chest pain, headache, nausea, palpitations, drowsiness, weakness, and bronchospasms in people with asthma. They conclude:
Taken together, these studies suggest that there may be a small number of people at risk for developing symptoms consistent with the ‘Monosodium glutamate symptom complex’ when consuming large amounts of MSG on an empty stomach without accompanying food. Importantly, the overall incidence of ‘Monosodium glutamate symptom complex’ appears to be low, even in self-identified MSG-sensitive patients [emphasis added]. Furthermore, current evidence does not suggest that this entity is associated with persistent or serious effects.
Williams and Woessner review the published studies on MSG and asthma and conclude:
To summarize, the bulk of the studies examining the potential role for MSG as a trigger of attacks of bronchospasm in asthmatics have failed to demonstrate an association. To date, no DBPC [double-blinded placebo-controlled] challenge-confirmed MSG-sensitive asthmatic has been reported.
As for uticaria (skin rash) and angio-oedema (swelling beneath skin surface), they conclude (2):
In contrast to the case for MSG as a cause of asthmatic bronchospasm, there does appear to be some evidence to suggest that MSG may be a rare cause of urticaria, and possibly angio-oedema.
Regarding rhinitis (inflammation of the nasal passages), there have been case reports of three people who, upon rigorous testing, appeared to get rhinitis from MSG. Not much more than that is known (2).
A more recent Cochrane Database System Review found no evidence that people with chronic asthma can benefit from avoiding MSG in amounts up to 5 g (3).
I spent some time trying to figure out how much MSG is typically in Chinese food and in nutritional yeast (as a reader asked about), but didn’t find anything.
In conclusion, MSG is not some sort of highly synthesized chemical – it’s just an amino acid that we are ingesting regularly from plant foods and probably nothing for most people to worry about in moderate amounts. In rare cases someone might have an allergic reaction to MSG.
I have 2 other posts on MSG which can be seen in the MSG Archive.
References
1. Beyreuther K, Biesalski HK, Fernstrom JD, Grimm P, Hammes WP, Heinemann U, Kempski O, Stehle P, Steinhart H, Walker R. Consensus meeting: monosodium glutamate – an update. Eur J Clin Nutr. 2007 Mar;61(3):304-13. Review. Erratum in: Eur J Clin Nutr. 2007 Jul;61(7):928. | link
2. Williams AN, Woessner KM. Monosodium glutamate ‘allergy’: menace or myth? Clin Exp Allergy. 2009 May;39(5):640-6. Epub 2009 Apr 6. | link
3. Zhou Y, Yang M, Dong BR. Monosodium glutamate avoidance for chronic asthma in adults and children. Cochrane Database Syst Rev. 2012 Jun 13;6:CD004357. Review. | link
November 16th, 2012 at 6:12 pm
Thanks for the detailed review! I’ve never been too concerned about MSG myself, but now I have some studies I can point my friends to if anyone ever raises concerns about it.
P.S. I’ve been following this blog for some months now and I appreciate your advice on a variety of topics.
November 16th, 2012 at 6:29 pm
Not only is it natural but it’s also a great addition to cooking. I recommend stir frying some greens with garlic, salt, and a dash of MSG. Delicious!
The MSG adds a sort of meaty flavor (yay, umami) that really improves the dish. I like to do this with spinach or the rape plant (worst name ever). You can buy rape plant greens at East Asian groceries along with MSG. It’s called “You Cai” in Mandarin and “Yau Choy” in Cantonese, so look for one of those names.
November 21st, 2012 at 1:06 am
Hello Jack. I eat too little iron. I read that dried thyme containes great amount of iron. Can I eat 10-15 gram of dried thyme daily? Is it healthy?
November 21st, 2012 at 11:05 am
Spinacz,
Dried, ground thyme has 5 mg of iron per tablespoon:
http://peacounter.com/foods_pub.php?ndb=2042
Adding some thyme to your diet seems like it wouldn’t be a bad idea, but 2-3 tablespoons a day should be unnecessary unless you have a very strange diet. If you are vegan, you should be getting plenty of iron in whole grains, leafy greens, and legumes. Adding vitamin C to your meals (like a small glass of orange juice) will significantly increase the absorption of plant iron. Here is more on iron:
http://veganhealth.org/articles/iron
November 22nd, 2012 at 10:13 am
I know it. I know what is good source of iron, what inhibits iron absorption and what strengthens this absorption. I eat a lot of legumes and whole grains, my daily iron intake is about 20-30 g. I don’t drink coffee and tea and I always eat good source of vitamin C, mainly red pepper, during meals which are rich of iron. Nonetheless, I have low level of iron. Last time when I checked my iron level I had normal but low level. (Norm was 50-150, I had 70). I have dark circles under the eyes and my hair are falling out. After I checked my iron level, I started taking iron suplement but this didn’t help. Maybe I have some metabolic problems. I don’t know.
November 23rd, 2012 at 10:24 am
Spinacz,
An iron level of 70 (and I assume you mean serum ferritin) shouldn’t cause you such problems. You might look into thyroid issues.