Re: Does sodium glutamate (an ingredient in Doritos) kill brain cells.

Dear Jose,

Monosodium glutamate (or MSG) is an extremely common food additive. In the food industry it is often referred to as a "flavor enhancer," because of a perception that it doesn't have a very distinctive taste of its own but rather acts to make other flavors in a given food item taste better. In fact, monosodium glutamate is even sold as a salt substitute. In the U.S. it is marketed under names such as Accent®.

Monosodium glutamate is the salt of glutamic acid, a simple amino acid. In the brain of all mammalian species, glutamic acid (known as glutamate in it's unprotonated or ionized form) is used as the most common excitatory neurotransmitter. Several years ago it was found that this neurotransmitter can kill neurons when it is present in excess. Currently, the role of glutamate in the damage and death of neurons after a stroke is an extremely hot topic of scientific investigation. However, glutamate does not cross the blood-brain barrier. Thus, no matter how much MSG you ate, it would never, ever kill any brain cells. Nevertheless, I suspect that a myth has grown up around the possibility that eating foods containing MSG could somehow harm your brain. This is simply untrue.

On the other hand, excess MSG has been shown to cause something like an allergic reaction that includes sweating and flushing of the face in susceptible people. This reaction is commonly known as "Chinese restaurant syndrome" because MSG is widely used in Chinese cooking. Some people can't really tolerate high levels of MSG in their food because of the uncomfortable feeling of heat and flushing when they eat a large Chinese meal. So these people either avoid Chinese restaurants, or ask to have their food prepared without MSG. This solves the problem, and apparently doesn't really affect the taste of the food negatively. Some Asian restaurants now even advertise that they don't use MSG at all.

I am not really aware of any other names that MSG can go under on an ingredient label, although there may be some. My bet would be that something like "natural and artificial flavor enhancers" would probably include MSG. But since it doesn't kill brain cells, there really isn't any reason to avoid it anyway.

As for pork meat, it also does not directly affect the brain, but over decades of eating meat products one can accumulate high levels of cholesterol, which increases your risk for heart attacks and strokes. So indirectly I guess you could say that pork is at least potentially harmful to brain cells. But it definitely won't do anything in the short term.

Hope this answers all your questions!

Joe Simpson
MD/PhD student, Neurosciences
School of Medicine
St. Louis, MO, USA

Addendum 3/24/99: It has been brought to my attention that MSG is in fact likely to be toxic to certain brain cells which are not adequately protected by the blood-brain barrier, such as the medial basal nucleus of the hypothalamus and the area postrema. There is a good deal of research suggesting the potentially harmful effects of MSG, but so far the FDA has not taken any action to restrict its use or the use of aspartame (Nutrasweet®, Equal®, etc.), which breaks down in the body to aspartate, an amino acid that has similar effects to those of glutamate.
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