Cassava contains more than one type of cyanide. Unless it's prepared properly, or if consumed in great quantities, this shrub can paralyze or even cause death.
Cyanogenic Glycosides
Cyanogenic Glycosides
Cyanogenic glycosides are a group of chemical compounds which occur naturally in over 2 000 plant species. There are at least 25 cyanogenic glycosides known to be found in the edible parts of plants. Cyanogenic glycosides alone are relatively non-toxic. However, as a result of enzymatic hydrolysis by beta-glucosidase following maceration of plant tissues as they are eaten, or by the gut microflora, cyanogenic glycosides are broken down to release hydrogen cyanide which is toxic to both animals and humans. The potential toxicity of a cyanogenic plant depends primarily on its capacity to produce hydrogen cyanide.
Symptoms of Cyanide Poisoning
In humans, the clinical signs of acute cyanide intoxication include rapid respiration, drop in blood pressure, rapid pulse, dizziness, headache, stomach pain, vomiting, diarrhoea, mental confusion, twitching and convulsions. Death due to cyanide poisoning can occur when the cyanide level exceeds the limit an individual is able to detoxify. The acute lethal dose of hydrogen cyanide for humans is reported to be 0.5 to 3.5 mg per kilogram of body weight. Children are particularly at risk because of their smaller body size.
Cassava contains more than one form of cyanogenic glycosides. Different varieties of cassava are generally classified into two main types: sweet cassava and bitter cassava. Sweet cassava roots contain less than 50 mg per kilogram hydrogen cyanide on fresh weight basis, whereas that of the bitter variety may contain up to 400 mg per kilogram. 
Chronic cyanide intoxication may lead to the development of certain conditions including disturbance of thyroid function and neurological disorders. It tends to affect those individuals who have regular long-term consumption of cassava with poor nutrition status.
Better Be Safe
Cassava contains more than one form of cyanogenic glycosides. Different varieties of cassava are generally classified into two main types: sweet cassava and bitter cassava. Sweet cassava roots contain less than 50 mg per kilogram hydrogen cyanide on fresh weight basis, whereas that of the bitter variety may contain up to 400 mg per kilogram. Sweet cassava roots can generally be made safe to eat by peeling and thorough cooking. However, bitter cassava roots require more extensive processing. One of the traditional ways to prepare bitter cassava roots is by first peeling and grating the roots, and then prolonged soaking of the gratings in water to allow leaching and fermentation to take place, followed by thorough cooking to release the volatile hydrogen cyanide gas. Cutting the roots into small pieces, followed by soaking and boiling in water is particularly effective in reducing the cyanide content in cassava. Whilst fresh cassava requires traditional methods to reduce its toxicity, adequately processed cassava flour and cassava-based products have very low cyanide contents and are considered safe to use.
Other Edible Plants Contain Cyanogenic Glycosides
Bamboo shoot is a popular food item among Asian population. The cyanogenic glycoside present in bamboo shoot is decomposed quickly in boiling water. Other edible plants containing cyanogenic glycosides include kernels within the pits of some stone fruits (e.g. bitter apricot kernels), lima beans, etc.
