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Cassava Culture

The cassava plant is the world's third most important crop. Although it originated in Brazil (where it is called manioc), it was brought to Africa by Portuguese colonists, and it is now an important crop there and in Indonesia and Southeast Asia. It is the principal source of nutrition for about 500 million people. Its leaves are edible but the prize is its starchy root, rich in protein, minerals and vitamins A, B and C.

Cassava enters the North American diet also - we make it into tapioca.

Surprising for an important edible plant, it is quite poisonous without proper preparation. The toxin in cassava is called linamarin. It is chemically similar to sugar but with a CN ion attached. When eaten raw, the human digestive system will convert this to cyanide poison. Even two cassava roots contain a fatal dose of poison.

To prepare cassava, it is peeled and grated and soaked in warm water for several days. This allows the cassava's own natural enzymes to convert the linamarin to sugar and cyanide gas, and the gas disperses harmlessly. What remains can be boiled and eaten, or more usually, dried and ground into flour.

Improperly prepared cassava was the cause of a mysterious disease called konzo, first discovered in Africa in the 1930s. It is really chronic low-level cyanide poisoning.