My friend believes MSG is harmful and on our discussion I sent him a video ted ed has made on the topic. To which he sent a research paper clearly saying MSG is not healthy. Link to the paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239414/
So, is MSG harmful or what?
No, MSG is not toxic - here are some sources on the matter:
https://www.sciencedirect.com/science/article/pii/S0195666310003089
https://ift.onlinelibrary.wiley.com/doi/10.1111/1541-4337.12448
https://www.sciencedirect.com/science/article/pii/S092846801730072X
https://www.sciencedirect.com/science/article/pii/S221226722100068X
https://www.andeal.org/vault/2440/web/Umami_Science_and_Lore_of_Health_Eating_201708.pdf
As for the article you linked:
> The average intake of MSG in UK was 0.58 g/day (6), 10.0 g in Germany (7)
This 10g/day figure seemed very high to me, so I tracked down the original paper that the claim comes from and it’s talking about 10g/day of L-glutamate (aka glutamic acid), which is an amino acid so is found in protein-rich foods and other foods such as tomatoes and cheese - only 0.3-0.5 g/day was added glutamate such as MSG.
Not really relevant to the question of safety, but it does allow me to
> Although the Food and Drug Administration (FDA) stated that MSG is a safe substance, several studies in animals have indicated negative effects after chronic consumption of MSG. These adverse effects have been shown in different organs such as thymus (9), brain (10), pancreas (11), testis (12), liver and kidney (13), and have been linked with several diseases including obesity, hypertension, headaches, asthma exacerbation, neurotoxic effects and detrimental effects on the reproductive organs (14).
Animal studies don’t necessarily translate to effects on humans - in fact, more often then not they don’t.
> It was suggested that uncontrolled use of food additives such as MSG can cause obesity (32). MSG has been used in several experimental models for inducing obesity which causes diabetes. Dietary MSG consumption is associated with obesity and overweight in healthy adults (33).
The only human study linked here is this one on 752 adults in China. I don’t know what the balance of evidence on the link between MSG and obesity is - certainly there are trials finding adding MSG to a meal decreases calorie intake, but these are limited and I don’t know of any others off the top of my head.
But even if the association is true, it’s not really surprising - the whole reason MSG is used is to make things highly palatable and encourage you to eat a lot of them. MSG does not appear to be inherently fattening, nor does this link make it toxic.
The rest of the linked studies regarding obesity and diabetes are on animals, with doses such as “Injection of MSG (2 mg/g body weight)” - this is equivalent to 150g of MSG for a 75 kg human, i.e. far, far more than anyone would be getting from their diet (which previously they discuss as being less than 1 g/day). As with any discussion of toxicity, the dose make the poison (and in this case the route; I get the feeling most people aren’t shooting up on MSG).
All studies on oxidative stress and hepatotoxicity (liver damage) are on rodents, as are the studies on neurotoxicity, genotoxicity, and reproductive toxicity (with the odd in vitro study thrown in). None of these results mean that it is toxic in humans.
To sum up, then, their entire thesis of MSG being toxic is supported exclusively by studies done in rodents or in a test tube, the only exception being as single human study that associates MSG with obesity which as I discussed above is not really surprising and does not make MSG toxic.
The balance of evidence shows MSG to be safe in sensible amounts in humans - if anything, there may be positive effects since I know of a couple of trials (1, 2) that showed using MSG in place of regular salt can reduce sodium intake - and [excess sodium intake is linked to millions of deaths each year](https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19\)30041-8/fulltext).
It’s safe! Some older and low quality studies said it wasn’t. However newer and better quality studies show it’s safe and even that people who claim to be sensitive to it are not. Since I learned this I’ve been cooking with it multiple times a week and it has caused zero issues for anyone.
The paper doesn’t clearly say MSG is not healthy. Chronic high doses in rats can have detrimental effects though.
A paper, especially in an obscure journal, doesn’t mean much. Look at the totally if the evidence. Almost everything out there shows MSG is safe. We all eat quite a lot of it, largely from natural sources, and the amount you need to reach toxicity is very high. Just look at some meta analyses. It’s incredible that this is still a topic of discussion.