A white powder with little taste of its own, monosodium glutamate is one of the world's most common food additives.

Chemically speaking, MSG is a sodium (salt) derived from glutamic acid (an amino acid, or protein). Commercially speaking, it's a powerful flavor enhancer used in everything from canned soup to takeout chicken.

MSG began its ascent to ubiquity in 1908, when a Japanese chemist found it produced a savory flavor, distinct from the sweet, sour, salty and bitter tastes recognized by gourmands of the time. He dubbed the flavor umami, Japanese for "delicious."

He noted that a sea vegetable that Japanese cooks had used for centuries was particularly rich in the stuff. Bam! Scientists went to work to extract it, and a multinational industry was born.

Though the Food and Drug Administration maintains that MSG is safe when consumed at typical levels, opponents blame it for maladies ranging from attention-deficit hyperactivity disorder to Alzheimer's. Avoiding it practically requires a Ph.D. in chemistry: MSG is a major component in a long list of additives with such names as hydrolyzed protein and autolyzed yeast.

Interestingly, the health risks of MSG came to light only after major food processors found ways to extract it cheaply. Japanese cooks had used sea vegetables for years with no apparent health problems, and one of the first published reports of "Chinese restaurant syndrome" came from a Chinese immigrant who first experienced symptoms after moving to the United States.

THAI PEANUT SAUCE

Do you love Thai food but hate the MSG headache?

Make your own creamy peanut sauce to serve with grilled chicken or pork, as a dip for cucumber slices, or tossed with a tangle of noodles. Add as much or as little crushed red pepper as you like.

4 teaspoons peanut oil

2/3 cup minced shallots

4 garlic cloves, minced

1/2 teaspoon crushed red pepper

6 tablespoons creamy peanut butter

2 tablespoons hoisin sauce

2 teaspoons dark brown sugar

3/4 cup water

1 tablespoon fresh lime juice

Heat oil in a heavy saucepan. Add shallots, garlic and crushed red pepper; cook over low heat until fragrant and just beginning to color, about 3 minutes.

Whisk in peanut butter, hoisin, brown sugar and water. Bring to a boil, reduce heat and simmer 1 minute.

Stir in lime juice.

Serve warm or at room temperature. Makes 11/2 cups.

-- Recipe by Laraine Perri

NUTRITION PER SERVING (2 tablespoons): 80 calories, 6 grams fat, 0 cholesterol, 2 grams protein, 6 grams carbohydrates, 1 gram fiber and 130 milligrams sodium.

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