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Lima Beans and Other Cyanide-rich Plants

Many kinds of plants employ cyanide-forming chemicals as protectants. Typical ‘cyanogenic’ chemicals taste very bitter, although the extent of bitterness is not a good indicator of toxicity. Animals that disregard the initial warning from bitterness are in danger of both acute and chronic cyanide poisoning. Let’s first consider the sorts of foods that can contain significant levels of cyanide. Then we’ll look at the differences between acute high-dose injury compared to chronic low-dose effects.

Lima beans

Lima beans can have dangerous levels of cyanide. However, the lima bean varieties that we can buy at the grocery have been specially selected for low-cyanide, so even improper cooking won’t result in poisoning.

It’s a different story in less developed areas where warm, humid conditions encourage the growth of seed-eating pests and where man- made pest-control chemicals are not used. There the local varieties of lima beans can contain twenty to thirty times higher concentrations of cyanogens . . .

Cyanide from Apples, Peaches and Almonds

Apple pips contain enough cyanide-forming chemicals to poison an occasional child. This seems to be a very rare occurrence. Stalks of maize and sorghum can contain high doses of cyanide, but this is mainly a problem for farmers feeding their cattle on residues left over after seed harvest. A sorghum-based pancake syrup produced in some country areas will be safe because the cyanide is lost during the lengthy boiling process.

On the other hand, there are genuinely hazardous cyanide levels in the kernels of apricots and peaches. Wise cooks are careful to pit these fruits before making jam. Some recipes, however, seem to call for intentional addition of tiny amounts of almond kernels. (I’m genetically a non-taster of cyanide, so cannot comment on any possible difference this makes to the final jam. No one with my genes would have survived under the Borgias.)