Can people eat acorns the way squirrels do?

Above, the question addressed by C. Claiborne Ray in her "Q&A" column last Tuesday in the New York Times Science section.

Brief answer briefer: Yes — and no.

The full story follows.

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Mighty Acorns

Acorns can be eaten by humans, but not raw, the way squirrels do, said Dr. Rui Hai Liu, a physician and an associate professor of food science at Cornell. Because of the tannins they contain, they can be very bitter and astringent.

Acorns were part of the diet of many Native Americans, Dr. Liu said, and were also sometimes eaten as a last resort by Chinese and Koreans, especially in springtime, when other foodstuffs were scarce.

“They are not a poison, but they are not suitable to be eaten raw,” Dr. Liu said. “Ideally, the tannins should be removed by soaking and cooking in water.”

Tannins, chemicals classified as polyphenols, precipitate proteins and interfere with their digestion. They may cause constipation or diarrhea in susceptible people, Dr. Liu said. Squirrels and deer eat acorns, but horses cannot, he said.

Different species of oak have acorns with different levels of tannin, with the North American white oaks generally considered to have sweeter acorns and the red oaks considered to have more bitter acorns.

Southwestern tribes still relish the sweeter acorns of species like Quercus arizonica, which they eat with minimal processing, sometimes as a stew. Acorns are rich in nutritious oils, which some tribes extract by boiling.