ORLANDO, Fla. (AP) _ Certain foods, even if eaten days before surgery, may slow down a person's ability to wake up from anesthetics, a researcher said Tuesday.

Foods such as potatoes, tomatoes and eggplants contain natural insecticides, called solanaceous glycoalkaloids (SGAs). The SGAs inhibit two enzymes in the body from breaking down the anesthetics, said Dr. Jonathan Moss, a University of Chicago anesthesiologist who led the study.

The study, presented Tuesday at the American Society of Anesthesiologists convention, may shed light on why some people wake up faster than others.

The enzyme, butyrlcholinesterase, is found in the blood and breaks down many anesthetic agents. The other enzyme, acetylvcholinesterase, breaks down a chemical vital for healthy nerve and muscle function.

When the enzymes are blocked, the body can't metabolize some anesthetics and muscle relaxants, the study found.

The study is based only on laboratory experiments with the enzymes and SGA.

Clinical tests on humans have yet to be conducted and Moss said people shouldn't let their diet worry them before surgery.

``This is really to help us understand why there is such a difference,'' Moss said. ``We don't want to scare anyone.''