 Suppose you're having a night out with friends. You go to a favorite Chinese food place downtown, order up some family style items, some beer, and catch up on each other's weeks. Suddenly someone flags down the manager and asks, do you use MSG in your food? The manager nods affirmative, and your friend announces that he refuses to eat here. He doesn't want a hole in his brain, he says. Maybe the whole group leaves. Maybe you stay and let your friend leave. If you do the latter, and you start to get a headache, either that day or the one after, what it starts you wondering about the MSG in the food? Maybe it really is bad for you. Maybe you should stop eating Chinese. If you read enough labels, though, you'll find MSG in a wide variety of processed foods, in restaurant cuisines, and in things as diverse as salad dressing, crunchy snacks, and soup. Are the food manufacturers trying to kill us with a poison? Why are people so worried about MSG? MSG, or monosodium glutamate, is a food additive. We'll get to it in a minute, but the story begins with Japanese professor Kadune Akita. He noticed that his wife's soup, her dashi, had a good distinctive flavor that she attributed to dried seaweed called kombu. That flavor he called umami, which roughly translates in Japanese as savoury, or deliciousness. What causes this flavor is glutamic acid, a natural amino acid found in a wide variety of foods naturally. Tomatoes have a high level, parmesan has buckets full, mushrooms, seaweed, meats, eggs, and soy are all abundant sources. This may explain why savoury sauces have a common element of flavor. Soy sauce, dashi, tomato, and parmesan, even the garam, a fermented fish sauce in ancient Roman cuisine, were all essentially abundant sources of umami flavor by virtue of their glutamic acid. Modern MSG is a commercial product that makes glutamic acid from virtually any protein source, including yeast, bacteria, or soy protein isolates. They are combined with common salt to produce a crystalline product that dissolves like salt or sugar, and can be added to canned or packaged food to give it extra flavor lost in processing. So why do some people worry about MSG? In 1968, a New England Journal of Medicine article described an anecdote of Chinese restaurant syndrome, the feeling of hangover and numbness that some people reported feeling after eating Chinese food. This led interested scientists to conduct tests looking for some underlying cause. One scientist, Dr. John Olney, found that if he injected extremely high levels of MSG into mice, there were changes to the nervous system, including erosions of the retina. MSG, it seems, is an excitotoxin. Excitotoxins are substances that cause damage to nerves by forcing them to fire too often, essentially exhausting the cell and causing it to commit cellular suicide called apoptosis. The chemistry of MSG allows it to be absorbed very, very quickly in the gut. Some of it entered parts of the brain, and at very high doses caused neurons to die. Additional studies confirmed that if rats were fed a diet that was 20% MSG by weight, they developed brain lesions and other neurological damage. These kinds of results are scary, no doubt. It will make you look twice if parmesan and tomatoes are your next bowl of dashi. Clearly, the FDA and watchdog groups need to revisit the generally accepted as safe classification it had received. However, some scientists pointed out that the initial studies were at ridiculous dosages. We know that the dose makes the poison. Also all studies had been done on rats, mice, or guinea pigs. What if humans processed MSG differently? Human tests were run, and at very high, but still achievable dietary levels. There were no short-term or long-term toxicities observed. However, it's always dangerous to assume doses, or extrapolate for long-term chronic effects. So, where does this leave us on MSG? Well, I think both sides have fairly legitimate points. Let me lay out the case. 1. MSG is an excited toxin. At very high levels, it can cause brain damage. 2. It levels that would be normal or even high in a diet. Humans don't appear to suffer any brain damage. 3. It's possible that genetic differences between us may influence our tolerance for MSG and other umami agents. 4. Children may have an increased susceptibility due to their brain development. I think it's perfectly legitimate to search labels for your very young children and look for MSG-free or low MSG products just to err on the side of caution. However, for adults, there's not enough evidence to say that MSG poses a serious risk. Websites claiming links to Lou Gehrig disease, MS, autism, or other diseases are not using good research to support their claims. There are two associations that are the subject of active research. One is obesity. In one study of Chinese villagers, obesity was correlated with MSG in diet. I have my doubts about the statistics here, but it bears mentioning. There's another study that suggests high MSG at a young age can be associated with obesity later in life. Other studies both on rats and humans contradict these studies, so I'd say it's still too soon to commit. There's also some evidence that in young mice, exposure to diets of 2% MSG, which again is a very elevated dose, causes various disorders of the eye. This effect can be reversed by certain other nutrients in the diet. For example, vitamin C is very protective. This is partly why I could understand the parent of a very young child having concerns. There have been studies showing MSG is not involved in asthma, autism, and cancer. Anti-testing has repeatedly disproved the wild claims often found on internet sites. So, coming back to Chinese restaurant syndrome, why do some people get it and others don't? Well, one clue comes from a double-blind study. 19 people who reported sensitivity were challenged with both a placebo and a high dose of MSG, 6 grams. They were asked if they felt any reaction. Only two of the 19 responded to the MSG, but not to the placebo. A similar study found that only 22 out of 61 responded to the MSG, but not the placebo. Six responded to both, 16 responded to the placebo only, and 18 responded to neither. This suggests to me that there is a certain psychological component to the effect. When we're sensitized to look for specific symptoms, we're quite likely to find them, a form of confirmation bias. MSG is just one controversial food additive. Another very similar substance is aspartame. Aspartame is an artificial sweetener known by many names in various countries, neutrosweet is a common one. It's also an excitotoxin, and also based on an amino acid, two actually, aspartic acid and phenylalanine instead of glutamic acid. One big difference is that it's not a naturally occurring substance. It's primarily made by the same company that owns the MSG market, Aginomoto. If you've ever seen the Informant with Matt Damon, this is the company involved in price fixing for Lysine with Archer Daniels Midland. So these are definitely big evil corporations, and that always sparks a controversy. Just like MSG, aspartame is toxic at very high levels, but at levels that would represent very heavy consumption, there haven't been any confirmed health effects. I'd still advise caution, don't overdo it, be aware of how much you're getting, and err on the side of caution with young children. So to conclude, there are food additives that at high levels are toxic, are excitotoxins. Attempts to pen down specific health effects have been largely unsuccessful, although the book is not yet closed on some issues. I wouldn't be too upset if we, as a country, decided to revisit these two substances. I don't think we need to stop all consumption, close every Chinese buffet, and ban Parmesan and Diet Coke. But I would feel better if baby food were MSG free. What do they need deliciousness for anyway? They're babies. So if you find yourself at a Chinese restaurant that uses MSG, don't sweat it. And if your friend really objects, suggest you all head to an Italian place. Then after he's eaten a giant pile of tomatoes, mushrooms, chicken and Parmesan, explain to him how he's just eaten more MSG than an entire buffet of Chinese food. It ought to be entertaining. Don't be surprised if your friend develops a sudden headache and hungover feeling. Thanks for watching.