Acorns are the nuts of oak trees and are edible. Though not a regular part of most people's meals, acorns have been part of the human diet for thousands of years.
Acorns were an important food source for ancient Greeks, the Japanese, the people of ancient Iberia and Native Americans. As of 2014, Koreans still use acorns to make jelly, acorn flour and acorn starch. Inside the acorn is usually one seed, which is surrounded by a hard shell. The nut can be boiled to remove the acorn meat. Acorns are believed to be a good source of fiber and may help lower blood-sugar levels.