Yams of the Dioscorea genus have many distinct compounds within the yam that makes it toxic to humans. These compounds consist of but not limited to: dioscorine, other alkaloids, flavonoids, phenols, phenolic acids, tannins, and oxalates. To remove these toxins, which can induce fatal paralysis, the Igbo people developed a “curing” technique.
- First the yam is boiled for a very long period often exceeding three hours depending on the heat intensity (many of the toxins above exhibit dipole and/or hydrogen bonding which allows for it to be water soluble). Boiling takes place in a pot lined at the top and bottom with leaves in such a way that the yam sits on a cushion of leaves (most likely to ensure that the toxins do not get left out)
- Boiling takes place usually in the evenings and the yam is left overnight and is never eaten hot or the day it is boiled.
- It requires special sauce (Nchá) which contains a lot of potash and plenty of palm oil. Lauric acid and tocotrienol (found in palm oil) both have positive benefits to the nervous system, perhaps reducing the risk of fatal paralysis caused by alkaloids found in yams.
- Consumers usually call the yam by its name before consumption, especially if they are not quite sure of the age of the tubers. They simply say “Nkóhū” (the name for bitter yam that has not been harvested the previous year) and proceed with the meal. It is believed that “calling” the yam by its name removes the possibility of dying after consumption as a result of a toxic reaction.
This elaborate preparation is still adopted by the more traditional Igbo in the heartland but the name nkóhū is not often pronounced before consumption.
Uzozie, Levi Chukwuemeka. “Tradition and Change in IGBO Food Crop Production Systems: A Geographical Appraisal.” University of London, ProQuest LLC, 2017, pp. 1–465.
Obidiegwu, Jude E, et al. Review of The Dioscorea Genus (Yam)—An Appraisal of Nutritional and Therapeutic Potentials, Foods, 16 Sept. 2020, pp. 1–45.
Osuagwu CG. Forest West African Indigenous Diet and Modernization Diseases. Functional Foods in Health and Disease 2019; 9(12): 772-787. DOI: 10.31989/ffhd.v9i12.673
Written by: Jonathan