Hard to say, easy to eat
Alright, the MSG questions just keep on coming so it’s time we put them to rest! Here’s what you need to know about consuming MSG, as a human.
While it's a commonly consumed ingredient, there are many claims about its potential negative impact on our health so I thought it would be helpful to discuss the background and clarify what's important to understand and what we can ignore.
What is it?
MSG is a combination of sodium and glutamate - the most common amino acid found in protein-containing foods. Since proteins are made up of various amino acids, it's no surprise that we're already exposed to glutamate if we consume protein. MSG provides a strong umami flavour, which is one of the five flavours and gives food a deep, savoury-style taste.
Although MSG occurs naturally in many foods, such as parmesan cheese, Vegemite, oyster, soy sauce, mushrooms, and tomato, the addition of higher doses or artificially created MSG added to food can start to make people worry.
The average intake of MSG in Western countries is about 0.3 to 2 grams a day, while in Eastern countries, its around 1.5 to 3 grams per day (from both natural and "unnatural" sources). These figures are essential when considering the claims made about MSG (see below)
Digestion and absorption
It's vital to understand how glutamate and MSG are metabolised, digested, and absorbed in the human body. Glutamate is metabolised and digested rapidly in the small intestine, so nothing typically passes beyond that point. If we consume a much larger dose of MSG, some may be metabolised by the liver, but nothing will escape the gastrointestinal system. Because of this, it's crucial to only consider studies where people orally consume MSG. There are a number of studies that inject MSG directly into the bloodstream or conduct tests on animals, which is in no way reflective of how we ACTUALLY consume it.
The use of rodent studies as "proof" is particularly frustrating, as mice metabolise MSG differently to primates (that’s you). Mice absorb more MSG into the bloodstream when they orally consume it since their gastrointestinal system doesn't digest and absorb it as effectively as ours does. Additionally, the blood-brain barrier - the barrier of cells surrounding our brain - is different between rodents and primates. The blood-brain barrier only allows "good things" to be transported across into our brain, and our blood-brain barrier is more effective than rodent blood-brain barriers. Therefore, claims made about MSG's impact on the brain based on studies conducted on rodents are often irrelevant to you, a non-rat.
Finally, dosages in these studies are often... intense. Remember how I said the high end of average daily intake is 3g per day? These studies typically use much, much higher dosages. One study gave rats a dosage of 500mg/kg of body weight. Speaking for myself, that's the equivalent of roughly 45g of MSG. A day. Let's ignore the fact that most humans feel sick at around the 60mg/kg of body weight mark, and again recall that we're consuming it ORALLY, meaning our stomach, small intestine and liver all get involved in the digestion and breakdown of the MSG. Madness.
Should I be worried?
If you're injecting in excess of 30g of MSG a day, possibly.
If you're consuming MSG through food, and not feeling sick, the only thing you're at risk of is an increase in the deliciousness of your food.
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