The mis-measure of manioc (Manihot esculenta,Euphorbiaceae)

The distinction between “bitter” and “sweet” (toxic and non-toxic) varieties of the cyanide-containing food crop manioc (Manihot esculenta, Euphorbiaceae) has a long tradition in the tropical forest areas of South and Central America where it was first cultivated. Yet this distinction has no taxonomic basis. The levels of cyanogenic glucosides found in manioc varieties not only vary widely, but do not correspond with any other known morphological or ecological feature. Nonetheless, these two “varieties” are commonly reported to have distinct geographical and cultural distributions and each is associated with a particular traditional food complex. This paper reviews the literature regarding the nature, distribution, and traditional uses of manioc varieties and concludes that (1) the geographical and cultural distribution of bitter and sweet varieties of manioc may not be as distinct as has been thought; (2) traditional categories of bitter and sweet manioc may stem more from culturally derived belief systems than from actual known levels of toxicity; and (3) the choice of complex and labor intensive processing methods usually associated with bitter manioc may not be required for detoxification but rather for the derived food products, particularly manioc flour.