apricot kernels

Yes, it's well-known that you can't make a horse drink if he or she doesn't want to, and apparently you can't get a man to stop taking a dangerous supplement — say one that produces cyanide when ingested — even when you tell him that it does so.

Apricot seeds are all over the internet - marketed as cancer fighters. But the seeds contain a chemical compound that, when ingested in high quantities (and by high we mean several seeds), can cause cyanide poisoning.