By Dr. Sylvia Baluka
Plant research is critical in identifying diets of plant origin without toxic substances so as to promote optimal human health and longevity.
Majority of food plants have potential toxicity, can provide precursors and activators of otherwise innocuous substances that can be modified into target organ toxins.
Some plants harbour more than one category of noxious agents e.g. the common vetch (Vicia sativa) contains a convulsant (beta-cyanoalanine) and cyanide liberating glycosides (vicianin and prunasin.
Toxic substances in plant foods can potentially be formed during post-harvest treatment, food processing, in the gastrointestinal tract of the consumer, during metabolism or in cells of the target organ itself.
Many plants contain toxic agents but communities that consume them have developed some local technologies that may be tedious, laborious and time consuming for processing and detoxifying these foodstuffs before they consume them.
The development of simple methods to detoxify cyanide-rich plant products has enabled their use as important food sources. For instance, Cassava is a major source of dietary carbohydrate for millions of people in Africa and South America.
The cyanide levels in unprocessed cassava are high enough to produce serious effects of cyanide poisoning including nervous signs such as mental confusion, muscular paralysis, and respiratory distress that are associated with chronic consumption. Detoxification of cassava is traditionally a multistep process that includes chopping, grinding or washing that help to remove the toxic chemicals.
Fermentation and boiling processes are also used among traditional procedures for production of cassava flour. Inspite having processing procedures that can greatly reduce the levels of hydrogen cyanide from cassava products, the hazard of chronic cyanide poisoning from cassava remains significant in some communities.
Thiocyanate toxicity from prolonged cassava consumption plus the combined effect of iodine and Selenium deficiency, is considered a contributory factor in goiter and endemic cretinism observed in parts of Africa.
Disadvantaged populations in developing countries including Uganda are more vulnerable to toxicity from plant foodstuffs because of their tendency to rely on monotonous diets derived from cheap environmentally tolerant and often potentially toxic plants.
For instance, in some communities or households it is possible to eat cassava prepared in different forms for breakfast, lunch and supper.
Disasters such as drought, floods and civil disturbances or war tend to escalate the over dependency on a single toxic drought resistant staple food crop such as cassava (Manihot esculenta) whose root tuber and leaves contain cyanogenic glycosides that are responsible for cyanide toxicity with consequences on the consumers’ health.
Plant toxicity varies with the maturity of the plant, soil characteristics and environmental conditions thus many communities have guidelines that they follow to reduce cassava toxicity; some potentially toxic cassava varieties are considered safe after staying for a certain number of years and therefore farmers are advised not to consume them before the recommended period so as to safe guard people and communities who live in areas with environmental conditions that favor plant toxicity.
However, for lack of alternatives, some households are compelled to consume cassava before the recommended period.
Noteworthy, variety in diet limits negative effects of potentially toxic foodstuffs such as Cassava.
As we promote cassava as a staple, we must ensure sustainable production of a variety of plant foodstuffs and animal products so that the human population can access and afford to eat a variety of plant foodstuffs and animal proteins in a single meal so as to minimize the toxic effects of cassava for Ugandans of the next generation.
Sustainability though difficult to achieve, is possible for plant foodstuffs if all the actors i.e. farmers, consumers, industrialists work together with environmentalists to minimize destruction of mother nature at a time when the world population is growing rapidly and the world is threatened to move several centuries backwards to a time when many countries and continents around the world experienced severe hunger and feminine.
Although many plants contain toxic agents, even more plants contain chemicals with medicinal properties that support homeostasis and act as antidotes to potentially toxic metabolites produced by the human body’s physiological activities thus ensuring optimal health and longevity for the human race.
That is why in Uganda we believe that our ancestors lived much longer and healthier lives despite not having access to health services because they survived on a natural diet.
It is incumbent upon scientists and researchers to show the way to the industry by utilizing the increasing knowledge and technology to tame nature to ensure sustainable food production across the world so that households and communities don’t have to depend on a single monotonous diet like cassava.
In addition they should use the wealth of the available knowledge to change the soil characteristics to ensure production of plant foodstuffs with minimal toxicity that will not be harmful to the consumers.
The ongoing research efforts to increase cassava growing and production should be matched by food safety research that promotes production and consumption of adequately processed and safe cassava products.
Dr. Sylvia Baluka is a lecturer at Makerere University
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