What is MSG?
MSG is short for monosodium glutamate. It is a common food additive-electronic number E621-used to enhance flavor. MSG is derived from the amino acid glutamic acid or glutamic acid, which is one of the most abundant amino acids in nature. Glutamate is a non-essential amino acid, which means your body can produce it. It performs various functions in your body and is found in almost all foods. Chemically speaking, MSG is a white crystalline powder, similar to salt or sugar. It combines sodium and glutamic acid and is called sodium salt.
The glutamic acid in MSG is fermented from starch, but there is no chemical difference between the glutamic acid in MSG and the glutamic acid in natural foods. However, the glutamate in MSG may be easier to absorb because it will not be trapped in the large protein molecules that the body needs to break down.
MSG enhances the salty and meaty taste of food. Umami is the fifth basic taste, as well as salty, sour, bitter and sweet. This additive is very popular in Asian cooking and is used in various processed foods in the West. The average daily MSG intake in the United States and the United Kingdom is 0.55-0.58 grams, and in Japan and South Korea is 1.2-1.7 grams.
Why do people think it is harmful?
Glutamate acts as a neurotransmitter in your brain. It is an excitatory neurotransmitter, which means that it stimulates nerve cells to transmit its signals. Some people claim that MSG can cause too much glutamate in the brain and overstimulate nerve cells. For this reason, MSG is labeled as an excitotoxin. The fear of MSG can be traced back to 1969, when a study found that injecting large doses of MSG into newborn mice caused harmful neurological effects. Since then, books such as Russell Blaylock's "Excitatory Toxin: Deadly Taste" have kept this fear of MSG alive.
Indeed, the increased activity of glutamate in the brain can cause harm-and large doses of MSG can increase the level of glutamate in the blood. In one study, a large dose of MSG increased the concentration in the blood by 556%. However, dietary glutamate has little effect on your brain because it cannot cross the blood-brain barrier in large quantities. 6 trusted sources).
Overall, there is no convincing evidence that MSG produces excitotoxins when consumed normally.
Some people may be sensitive
Some people may experience adverse reactions due to consumption of MSG. This condition is called MSG symptom complex.
In one study, people who self-reported that they were sensitive to MSG consumed 5 grams of MSG or a placebo—36.1% of people reported a response to MSG, compared with 24.6% of placebo. Symptoms include headache, muscle tightness, numbness, tingling, weakness, and flushing.
The threshold dose to cause symptoms seems to be around 3 grams per meal. However, keep in mind that 3 grams is a very high dose—about six times the average daily intake in the United States. It is not clear why this happens, but some researchers speculate that such a large dose of MSG allows trace amounts of glutamate to cross the blood-brain barrier and interact with neurons, causing brain swelling and damage.
Some people claim that MSG can also cause asthma attacks in susceptible people. In a 32-person study, 40% of participants had asthma attacks due to high-dose monosodium glutamate. However, other similar studies have not found any relationship between MSG intake and asthma.
Impact on flavor and calorie intake
Certain foods are more full than others. Eating filling foods should reduce your calorie intake, which may help to lose weight. Some evidence suggests that MSG may help you feel full.
Studies have shown that people who consume MSG flavored soup consume fewer calories in subsequent meals. The umami taste of MSG may stimulate receptors in the tongue and digestive tract, triggering the release of appetite regulating hormones. In other words, other studies have shown that MSG will increase—not decrease—calorie intake. Therefore, it is best not to rely on MSG to help you feel full.
Effects on obesity and metabolic disorders
Some people associate MSG with weight gain. In animal studies, injecting high-dose monosodium glutamate into the brains of rats and mice can cause them to become obese. However, this has little to do with the human dietary intake of MSG (if any). In other words, several human studies have linked MSG consumption to weight gain and obesity.
In China, the increase in MSG intake is related to weight gain-the average daily intake is between 0.33-2.2 grams. However, among Vietnamese adults, an average daily intake of 2.2 grams has nothing to do with being overweight.
Another study linked increased MSG intake in Thailand to weight gain and metabolic syndrome-but it has been criticized for methodological flaws.
In a human controlled trial, MSG increased blood pressure and increased the frequency of headaches and nausea. However, this study used unrealistically high doses.
More human studies are needed before the link between MSG and obesity or metabolic disorders can be fully stated.
Depending on who you are asking, MSG is either completely safe or a dangerous neurotoxin. The truth is somewhere in between.
There is evidence that the right amount of MSG is safe. However, large doses may cause harm. If you have an adverse reaction to MSG, you should not consume it. That is, if you do not experience side effects, there is no compelling reason to avoid it.
Remember, MSG is usually found in processed low-quality foods-you should avoid or limit these foods anyway.
If you have eaten a balanced diet with a lot of whole foods, you don't have to worry about high MSG intake.