Ambrosia was the legendary food of the gods which granted them immortality. It was also the food eaten by the Centaurs, and Satyrs.
Amanita Muscaria and Panaeolus Papilionaceus, two mushrooms which grow in Greece, have hallucinogenic properties. They also induce violence, deep spiritual visions, increased sexual energy, and considerably augment physical strength. This goes far in explaining the myths that convey the Centaurs as a violent race, and also helps to explain their mystic nature that seemingly conflicts with their penchant for violence. These same mushrooms are believed to have been utilized by the Norse Berserkers to augment their strength in battle. The image of this mushroom appears on some art depicting centaurs, including vases and other decorated clay medium.
As the cult of Dionysus grew its followers were sworn to secrecy about what went on at the ceremonies. They often had visions and believed that they were promised immortality.
The Masatec Indians have a god named Tlaloc, the mushroom god. His worship entails eating a hallucinogenic mushroom closely related to the one present in Greece. An eerie parallel is present between the Masatec and early Greek religion. Both Tlaloc and Dionysus were born of lightening, and in both cultures it is believed that mushrooms came from lightning. Both the Greek ambrosia and the Masatec ritual mushroom are reffered to as "Food of the Gods." It seems very likely that these "Magic Mushrooms" have been responsible for concepts of Heaven and Hell in both Europe and the Americas.
Graves, Robert. The Greek Myths. London: Folio. 2002.