Metabolic fates in humans of linamarin in cassava flour ingested as stiff porridge

Insufficiently processed products from cassava roots may contain residual a mounts of cyanogenic glucosides, mainly linamarin. The fate of orally inges ted linamarin nos studied following a meal of cassava porridge prepared fro m cassava flour from southern Tanzania with 82 mg cyanide equivalents (3035 mu mol) of linamarin per kg dry weight. Following ingestion of amounts of porridge containing 243-571 mu mol linamarin by 15 healthy adults a mean (r ange) of 21% (1-47%) of the linamarin ingested was excreted in the urine wi thin 24 hours and a mean of 1% in the nest 24 hours. Serum thiocyanate, the main cyanide metabolite, increased in all subjects from a mean (+/- SD) of 31+/-6 to 78 +/- 28 mu mol litre (P < 0.001). In a second group of seven s ubjects we found that the ingestion of porridge with a mean (range) of 431 mu mol (203-669%) of linamarin resulted in a mean linamarin excretion of 12 7 mu mol/litre and an excess thiocyanate excretion of 118 mu mol/litre and that 216 mu mol was un accounted for. We conclude that less than one-half o f orally ingested linamarin is converted to cyanide and hence thiocyanate, about one-quarter is excreted unchanged and another quarter is metabolized into an as yet unknown compound. (C) 1999 Elsevier Science Ltd. All rights reserved.