Q: Do avocados contain a lot of cholesterol?

A: Cholesterol is found only in animal foods, and therefore avocados have none at all. But unlike other fruits, they do contain oil, which is what makes them relatively high in calories. Just how much oil they hold can vary quite a bit. California avocados, by law, cannot contain less than 8 percent fat. But the seasonal variation is considerable, and the fat content can run as high as 20 percent. Florida, on the other hand, has no such standards for its avocados, which tend to be lower in fat.

On average, three ounces of raw California avocado, or about half of a fruit weighing eight ounces (including pit and skin), would have about 153 calories, 134 of them from fat, and nearly all the rest from carbohydrate. By contrast, the same amount of Florida avocado would contain about 95 calories, 68 of them from fat. Since Florida avocados tend to be much larger, this would be slightly less than 33 percent of a one-pound fruit.

While avocados apparently are native to Mexico, they were not produced commercially in this country -- in Florida -- until the turn of the century.

Q: What can you tell me about a new sweetener discovered recently in Mexico?

A: A systematic search of Mexican ethnobotanical literature led A. Douglas Kinghorn and coworkers at the University of Illinois in Chicago to the discovery of an intensely sweet plant.

In a volume called "Natural History of New Spain," written between 1570 and 1576, the Spanish physican Francisco Hernandez described a remarkably sweet plant known to the Aztec people by the Nahuatl name of Tzonpelic xihuitl, or "sweet herb." It was later classified botanically as Lippia dulcis, Trev.

The investigators named the sweet component of the plant (a colorless oil present mainly in the leaves and flowers) hernandulcin, in honor of Dr. Hernandez.

To date, the chemical structure has been identified, and it has been synthesized in the laboratory. It has been found to be nontoxic to mice and did not produce mutations, or abnormal changes in bacteria. Preliminary studies with human taste panels revealed it to be 1,000 times as sweet as sucrose. But it was evaluated as less pleasant than sucrose and exhibited off-tastes and aftertastes, as well as some bitterness.

Nevertheless, this structurally simple and intensely sweet molecule, which can be synthesized easily in the laboratory, is expected by those who identified it to serve a useful function in increasing our understanding of the relationship between chemical structure and sweetness. Perhaps it may also contribute to the design of a safe and acceptable alternative to sugar. Its potential beyond that remains unclear.