Cyanogenic glycosides are naturally occurring compounds found in various plants. While not inherently toxic, they can release hydrogen cyanide, a poisonous gas, under specific conditions. Understanding these compounds is important for safely handling and consuming foods that contain them. This article explains their presence in common foods, how toxicity occurs, the health effects of cyanide exposure, and methods to minimize risk.
Where Cyanogenic Glycosides Are Found
Many common food sources naturally contain cyanogenic glycosides, with concentrations varying significantly. Cassava, also known as yuca or tapioca, is a widely consumed root vegetable containing linamarin and lotaustralin. Bitter almonds have high amygdalin levels, distinguishing them from sweet almonds.
Other fruits with stone pits, like cherries, apricots, peaches, and plums, also contain these compounds within their kernels. Flaxseed is another source, containing linamarin, linustatin, lotaustralin, and neolinustatin. Bamboo shoots, often used in Asian cuisine, contain taxiphyllin.
How Toxicity Occurs
Toxicity arises when plant tissue is damaged, allowing specific enzymes to interact with cyanogenic glycosides. When foods containing these glycosides are crushed, chewed, or digested, beta-glucosidase contacts the glycoside. This enzymatic reaction breaks down the glycoside, releasing a cyanohydrin.
The cyanohydrin then decomposes to produce hydrogen cyanide (HCN), the compound responsible for toxic effects. HCN release can also occur in the gut through intestinal bacteria, even if plant enzymes were inactivated by stomach acid.
Health Effects of Cyanide Poisoning
Exposure to hydrogen cyanide leads to a range of symptoms, with severity depending on dose and individual factors. Mild symptoms include headache, dizziness, nausea, and vomiting. Individuals might also experience confusion, anxiety, or a rapid heart rate.
More severe exposure can result in difficulty breathing, seizures, and loss of consciousness. In extreme cases, cyanide poisoning can lead to cardiac arrest and be fatal. Symptoms typically appear rapidly, from seconds to minutes after exposure. Long-term, chronic exposure to lower levels, such as from consuming improperly processed cassava, can lead to neurological issues like numbness, poor muscle control, and vision or hearing loss.
Reducing Your Risk
Several methods can significantly reduce cyanogenic glycoside content in foods. Peeling the outer layer of plants like cassava helps, as glycosides are often more concentrated there. Soaking foods in water for several hours or overnight allows water-soluble glycosides to leach out; discarding the soaking water further minimizes cyanide.
Thorough cooking methods, such as boiling, baking, or roasting, are effective. Heat inactivates the beta-glucosidase enzyme, causing released hydrogen cyanide gas to volatilize and dissipate.
Fermentation, particularly for foods like cassava, involves microorganisms that break down glycosides into less toxic compounds. Avoid consuming raw or unprocessed bitter almonds and large quantities of certain fruit pits, as these contain high concentrations of cyanogenic glycosides that pose a greater risk.