Q. Does Ajinomoto, or monosodium glutamate, cause any health problems? How is it made?

A. Glutamate is an amino acid found naturally in almost all foods, especially cheese, milk, meat, peas, tomatoes and mushrooms. MSG is produced by fermenting starch, sugar beets, sugar cane or molasses — the same process used to make beer, vinegar, soy sauce and yogurt. Fermentation breaks those things down, producing glutamate, which is then mixed with salt to produce monosodium glutamate.

In 1968, Ho Man Kwok, a Chinese physician, published an article in the New England Journal of Medicine describing symptoms he felt after eating at American-Chinese restaurants.

"The most prominent symptoms," he wrote, "are numbness at the back of the neck, gradually radiating to both arms and the back, general weakness and palpitations ..."

He suggested that MSG could be the cause since it is widely used in Asian foods — Ajinomoto was invented in Japan in 1909 by national hero Kidunae Ikeda — and the tenuous connection became known as Chinese restaurant syndrome.

Several books and television news programs started reporting widespread, and sometimes life-threatening, reactions to MSG.

A problem with the unconfirmed reports is that it's difficult to link the reactions specifically to MSG. Most are cases in which people have had reactions after, but not necessarily because of, eating foods containing MSG. Such reports are not the result of controlled studies done in a scientifically credible manner. For example, the reactions may be caused by ingredients such as shrimp, peanuts or spices.

Many people who believe they are affected by MSG come down with headaches or nausea if they think the food they're eating contains MSG — even when the food is MSG-free.

The proper way to study the issue is to give people foods with or without MSG and not tell them which food they're eating, then see if they indeed have reactions or problems only after eating the MSG-spiked foods. This is what scientists call placebo-controlled trials.

When people claiming to have reactions to MSG were placed in placebo-controlled trials, it was found that they did not have reproducible reactions to MSG-containing foods. Reactions did occur after eating 3 grams or more of MSG on an empty stomach, but a typical serving of food cooked with MSG contains less than half a gram of the flavor booster. And the body produces 50 grams of glutamate a day — it is a building-block of proteins vital for growth and brain function.

There is no evidence that MSG damages nerve cells or causes brain lesions, Alzheimer's disease, hyperactivity or any other chronic disease.

The bottom line: The Chinese Restaurant Syndrome is likely a myth, but there are always rare exceptions. If you find that MSG causes problems, then avoid it.

Dr. Landis Lum is a familypractice physician for Kaiser Permanente and an associate clinical professor at the University of Hawai'i John A. Burns School of Medicine. Send your questions to Prescriptions, Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.