Beating the MSG clock.

Beating the MSG clock

Monosodium glutamate (MSG), the flavor-enhancer used in Chinese restaurants and elsewhere, is a well-known neurotoxin capable of inducing convulsions when injected into a test animal's abdominal cavity, or peritoneum.

MSG's convulsive effects on rats are well studied, and the doses needed to get those effects are remarkably predictable, depending on the rat's age, weight and pedigree. Irma De la Rosa, Alfredo Feria-Velasco and their colleagues at the Unidad de Investigacion Biomedica de Occidente in Guadalajara, Mexico, suspected another variable might affect MSG toxicity: time of day.

The researchers injected standardized doses of MSG into rats' abdominal cavities at 7 a.m., 3 p.m. and 11 p.m., then kept track of the number and severity of seizures. They recorded no differences in the total number of seizures in each group, but convulsions were far more severe in the 7 a.m. group. Indeed, nearly 70 percent of the MSG-for-breakfast group died of epileptic seizures, suggesting a critical interaction between MSG and one or more of the many chemicals in the body whose concentrations vary with time of day. There were no deaths in the other two groups, and control rats injected with equivalent solutions of table salt had no seizures.

While it's tempting to rule out Chinese food for breakfast, extrapolation to humans is difficult because experimental doses were more than 50 times those one might expect from a meal, and because MSG -- when not injected -- is largely detoxified in the digestive tract.