Cassava / Manihot esculenta
Family: Euphorbiaceae
Cassava is a perennial shrub that grows to 8 feet.1 It has big fleshy roots, woody stems, large palm-like leaves, and green flowers.2 Native to Central and South America, cassava is currently grown throughout Western and Central Africa, in an area commonly referred to as the ¡§cassava belt¡¨.2,3 Large-scale production of the plant is currently underway throughout South America, China, Indonesia, Vietnam, and Africa.3 There are two varieties of cassava, the bitter and the sweet, but in both cases, it is the root of the plant that is used for its nutritional and medicinal value.1,2,3
History and Cultural Significance
Cassava roots have been used traditionally in South America as a food source, primarily for starch. Researchers estimate that cassava may have the maximum concentration of starch, about 30%, on a per weight basis, more than any other food source.4 Tapioca is the traditional Brazilian name for cassava.2
Some cassava roots contain a potentially fatal concentration of toxic substances that, if eaten raw, can result in vomiting, sweating, and difficulty breathing.3,4,5 These toxins can be removed from the root by slicing, pressing, and washing the root or by cooking root pieces and discarding the resulting wash water.1,2,3,4 Other varieties of cassava have a much lower concentration of the toxins and can be safely eaten raw. Due to difficulty discriminating between the varieties, many native cultures who rely on this plant as a source of food prepare all cassava in the same manner.1,3
Traditionally, the native people of Columbia employed the toxic water resulting from the washing of the bitter root as a fish poison.2 The flour was made into a paste and used to treat blisters and sores and as a component of a Chinese medicinal product to draw out pus from skin infections.2 The juice of the bitter root, after being boiled and allowed to ferment in the sun, was used as a preservative for meat.1
Currently, cassava is primarily a food source and provides basic sustenance in poorer areas.3 The roots are peeled and baked, boiled and fried.4 They are also sliced, washed, dried, and ground into a flour which is used for making flatbread1,4 or as a thickening agent in cooking.2,3 The flour is also used as an animal feed.2,3
Modern Research
Currently no clinical studies are available on the internal or external use of cassava. Future studies may build upon recent in vitro research examining the antioxidant properties of cassava.6
Future Outlook
There are a variety of native pests that threaten the cassava plant including African grasshoppers, hornworms, whiteflies, and the root-feeding burrower bug.3 It was thought that toxins contained in the bitter cassava plant and root were a natural deterrent for insects and animals, but this is currently considered speculative.3 Research has shown that African grasshoppers and root-feeding burrower bugs prefer the plants that have a lower concentration of the cyanogenic glycosides, but other pests like hornworms and whiteflies feed on bitter and sweet cassava.3
Despite the resilience of natural predators and lack of education among small independent producers of cassava in poorer areas, the world production of cassava grew 2.2% to almost 173 million metric tons in 2000 compared to a little over 169 metric tons in 1999.3,7 The largest producers of cassava are Nigeria (18.9%), Brazil (13.3%), and Thailand (10.7%).7 The price of tapioca in 2003 of $94 per metric ton was still lower than the 10 year average of $118 per metric ton, but consistently higher than the two previous years. Despite the fact that cassava is considered the fourth most important source of carbohydrates for the tropics behind rice, sugar, and maize, the world market for cassava starch and meal is limited because of abundant substitutes. This may explain why world exports of tapioca fell to 3.6 million metric tons in 2002 from 5.1 million in 2001.3,4,7
References
1 Grieve M. A Modern Herbal. Vol 1. New York: Dover Publications Inc.; 1971.
2 Chevallier A. The Encyclopedia of Medicinal Plants. London: Dorling Kindersley Ltd.; 1996.
3 Bellotti AC, Smith L, Lapointe SL. Recent Advances in Cassava Pest Management. Annu Rev Entomol. 1999;44:343-370.
4 O¡¦Hair SK. New Crop FactSheet: Cassava. Tropical Research and Education Center. Homestead, FL: The University of Florida; 1998. Available at: http://www.hort.purdue.edu/newcrop/CropFactSheets/cassava.html. Accessed April 25, 2005.
5 Epstein H. Crippling Harvest. Natural History. July 1996:12-15.
6 Rahamat A, Kumar V, Fong LM, Endrini S, Sani HA. Determination of total antioxidant activity in three types of local vegetable shoots and the cytotoxic effect of their ethanolic extracts against different cancer cell lines. Asia Pacific J Clin Nutr. 2003;12(3):292-295.
7 Cassava. CRB Fundamentals-2004 Commodity Articles. The Commodity Research Bureau web site. Available at: http://www.crbtrader.com/fund/articles/cassava.asp. Accessed April 20, 2005.