CHICAGO--"Nanofoods" now on the market promise everything from mouth-watering bursts of flavor to fresher produce, but speakers at the 2009 AAAS Annual Meeting said very little is known about how tiny particles added to foods and food packaging might affect human health.

There are nearly 800 commercial products that contain nanomaterials--particles so small that 80,000 of them could line up comfortably across the width of a human hair.

So far, nanofoods and food packaging with nanoparticles make up only 10% of this total, but worldwide sales of nanofoods "are expected to reach U.S. $6 billion by 2012," said Qasim Chaudry, a food safety scientist at the Central Science Laboratory in the United Kingdom.

Nanofood manufacturers want to include the particles as flavor boosters, replacements for fats and sugars, delivery systems for vitamins, and in the case of packaging, coverings that keep foods fresher for longer and may someday act as sensors that tell a consumer when their food is starting to spoil.

It's unlikely that nanoparticles would ever be used for "unlimited synthesis of foods assembled from atoms and molecules," Chaudry said, noting that they would take too much energy to manufacture.

But what happens to a nanoparticle once it is eaten? Researchers know that nanomaterials have unique properties as a result of their tiny size, including vastly enhanced surface area and different kinds of chemical reactivity than their bulk counterparts.

Expanded surface area can help a cocoa-dusted nanoparticle taste like a rich mouthful, but it's still unclear what happens to a nanofood after it is swallowed, said Hermann Stamm, a risk assessment researcher at the European Commission's Joint Research Center.

Stamm cautioned that there are "extremely limited studies" on how nanoparticles are absorbed by the body's tissues, and "only a narrow range of effects have been studied" for a few types of particles such as nanosilver.

Without studies showing how these products might affect human health, it can be difficult to devise safety regulations for nanofoods, said Thane Scott Thurmond, a food safety researcher at the U.S. Food and Drug Administration.

Other questions "do exist regarding the regulatory status of these products," Thurmond suggested. For instance, if a substance has already been deemed "generally recognized as safe" by the FDA, would that seal of approval automatically be conferred to nanosized versions of the product?

It's a question that the FDA is reviewing, said Thurmond, who said the agency is expected to issue guidance on the topic by the end of the year.