MSG is slightly more dense than sugar, with a specific gravity of 1.6 and comes in a crystalline form that resembles sugar.
4 grams of sugar is about a teaspoon, and the same can be expected of MSG. They can easily dump half a teaspoon of the stuff into your soup or sauce in a restaurant, treating it like salt or sugar.
This amazing paper is valuable not just for its work on rats, but for its references.
It's also noteworthy that the researcher basically considers it a settled question that MSG causes headaches.
In this work, she isn't trying to answer the question "do rats get a headache from MSG".
You'd have to be crazy to add 2.5 grams worth of MSG to a single meal. Accent calls for using like 1/10th that amount in soup. That's no different than using 10x as much salt as a recipe calls for, it's not going to turn out so great.
Depending on the size of the pot that might be about right. The problem I have with the studies referenced is that they wildly overestimated MSG intake and their threshold effect was at a level similar to eating one of those heaping tablespoons of MSG by itself with no food. I'm sure MSG produces some noticeable effect at some point but those studies make it seem like the threshold they found was consistent with the amount you could plausibly eat in a normal meal seasoned with MSG.
That's something like 40 to 50 grams. Say it's an 8 liter pot, serving 16. That's like 2.5g to 3.1g per person, ouch! Then there is glutamate in that pot already from natural sources as well as possibly ingredients like processed meats and whatnot.
No, it's actually more like 24g to ~30g depending on how "heaping" the tablespoons were, you might be thinking of the specific gravity and using that to estimate the weight but an important consideration is that it's in a small crystalline form. 1/4 tsp of MSG is 1.0g which puts a tbsp at 12g. An estimate of only 16 servings is probably a bit on the low side as well. Even assuming all of that, that still only amounts to 24 mg/kg for a 70kg person whereas the paper you referenced indicated there was a threshold effect and used doses of 150 mg/kg.
> might be thinking of the specific gravity and using that to estimate the weight but an important consideration is that it's in a small crystalline form
I'm relying on the density of MSG being similar to that of sugar, and both being in crystalline form, then working from information around the web about the mass of heaped tablespoons of sugar.
(I know that not all crystals are of the same shape and not all pack the same. Something with needle-like crystals will end up fairly fluffy, unless mechanically crushed.)
In the paper I cited there is a reference to another one by Shimada, et al. 2013. Those researchers estimate the daily intake of MSG in industrialized countries to be between 50 mg/kg and 200 mg/kg. (That reference is given in section 2.4.1, p. 76).
So you're saying that MSG doesn't cause headaches, because nobody would be crazy enough to put 2.5 grams of it into the meal consumed by a 50 kg person? Or what is the logic here?
The paper cites at least two other studies which found that 150 mg/kg daily doses caused headaches: to 100% of the subjects in one of the studies, and more than 50% in the other.
The paper you cited references three other papers. The first paper just throws out an estimate with no source or data for it, just a figure. That figure is also not in mg/kg just total dietary intake. Honestly the figure itself is believable as it claims 0.3g to 1.0g per day which works out to 4.3mg/kg to 14.3 mg/kg for a 70 kg person.
The second paper isn't listing MSG or even just free glutamate, it's listing all glutamate content which as you pointed out in another comment, is not comparable.
The third paper cited appears to be where they got their wildly wrong claim of 50 mg/kg to 200 mg/kg from but this literally just cites the first two papers. I'm assuming they just converted the glutamate figures in the second paper and assumed all of that was MSG.
Either way the claim that average daily intake of MSG is between 50 mg/kg and 200 mg/kg is just flat out unfounded and wrong. The very first source they cite lists a figure less than 1/10th that amount and obviously does not support their claim. And keep in mind, a 150 mg/kg dose for an average person is 10.5 g, that's over 20x the recommended serving size.
If it truly is a settled question that MSG causes headaches in humans, when the MSG is ingested (not injected) in amounts humans normally eat, then it should be easy to find studies in reputable journals to this effect. Do you have a link to such studies?
The injection/ingestion distinction is important, because when one ingests something, the entire quantity is not instantly dumped in to the bloodstream as it is when injected. The food MSG is ingested with might also have an effect on its rate of absorption and its effects. It might also undergo some changes in the digestive tract before it gets in to the blood stream.
Because this particular researcher is looking for very specific effects, that she's trying to measure accurately. She's shaved an area of the rat's skulls down to a thin window through which she's able to observe blood flow changes.
> Do you have a link to such studies?
This paper has a bunch of these types of references; for that alone it's useful. See section 2.4.
By the way, injection would be a good way to double-blind an MSG experiment with humans properly: you can't taste an injection. Nobody can tell whether they are being injected saline or MSG.
And nobody is claiming that the effects of MSG are not dose-dependent; that there is no consumption threshold below which sufferers feel no ill effects. Those who believe that any amount of MSG, no matter how miniscule, can cause them discomfort are deranged. If it were so, they would get these effects from all sorts of common foods that naturally contain glutamate.
MSG is slightly more dense than sugar, with a specific gravity of 1.6 and comes in a crystalline form that resembles sugar.
4 grams of sugar is about a teaspoon, and the same can be expected of MSG. They can easily dump half a teaspoon of the stuff into your soup or sauce in a restaurant, treating it like salt or sugar.
This amazing paper is valuable not just for its work on rats, but for its references.
It's also noteworthy that the researcher basically considers it a settled question that MSG causes headaches.
In this work, she isn't trying to answer the question "do rats get a headache from MSG".