Critics charge that MSG causes diabetes, headaches, or obesity. But are these claims true?
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This is the second in a two-part article on monosodium glutamate, or MSG. As I discussed last week, MSG is an ingredient made of salt and the amino acid glutamate that’s used to enhance the flavor of foods. The reason it has this effect is that your tongue has special flavor receptors that respond specifically to glutamate. Glutamate is found naturally in foods like parmesan cheese and tomato juice and has several important functions in the body—including acting as a neurotransmitter in the brain.
The U.S. Food and Drug Administration, as well as various international food safety and health agencies, consider MSG to be perfectly safe when used as a food additive or flavor enhancer. In fact, adding a little MSG can help manufacturers reduce the sodium in processed foods without sacrificing flavor.
However, a lot of people charge that MSG is not harmless—causing headaches, flushing, and other temporary but unpleasant reactions in people who are sensitive to it. There are also concerns that it may cause neurological damage, diabetes, or even be linked to the obesity epidemic. Today, I want to take a closer look at the evidence used to support these charges.
Does MSG Cause Neurological Damage?
Concerns about the effects of MSG on the brain appear to stem from an early experiment in which researchers injected newborn mice with very large amounts of MSG. The mice developed brain lesions. That’s never a good sign. Of course, the experiment was not repeated on humans but based on this preliminary data, I feel very comfortable concluding that we should not inject huge doses of MSG into babies—or adults for that matter.
However, when MSG is consumed as part of the diet—even at levels hundreds of times above normal consumption patterns—it does not appear to cause brain lesions or any other neurological changes in mice or any other animals that they’ve tried it on, including humans.
Because glutamate acts as a neurotransmitter, it might seem logical that eating large amounts of it could flood your brain with too much of a good thing. However, your brain is protected from this and other indiscretions by something known as the “blood-brain barrier,” a sort of filter that prevents compounds in your blood (such as glutamate) from crossing into your brain.
In other words, the levels of glutamate in your brain stay fairly constant regardless of how much or how little glutamate or MSG you consume. That’s why it’s unlikely that dietary MSG would have any direct effect on brain function.