Acute Cycas seed poisoning in Taiwan

J Toxicol Clin Toxicol. 2004;42(1):49-54. doi: 10.1081/clt-120028744.


Objective: The seeds of cycads contain cycasin and neocycasin, which belong to the family of cyanogenic glycosides. These glycosides of cycads are considered pseudocyanogenic with little potential to liberate hydrogen cyanide as other cyanogenic glycosides do. This study investigated the clinical spectrum of Cycas seed poisoning and its cyanogenic potential.

Methods: This was a retrospective chart review conducted at the Poison Control Center in Taiwan (PCC-Taiwan) from 1990 to 2001.

Results: Twenty-one cases of Cycas seed poisoning were identified. The reasons for seed ingestion were misuse as an edible food (70%), health promotion (10%), cancer prevention (10%), cosmetic use (5%), and gastrointestinal discomfort (5%). All patients had eaten the seeds after washing and cooking them. The time from ingestion to the onset of symptoms ranged from 30 min to 7 h (mean 2.8 h); patients had ingested between 1 to 30 seeds. Respiratory depression did not occur. Severe vomiting was the most striking symptom. All patients except one presented with gastrointestinal disturbance, and 90% sought medical care at the emergency department. Within 24 h, all patients had recovered. Six patients had blood cyanide or thiocyanate levels measured. Although the levels were higher than normal, they did not reach the toxic range.

Conclusions: The cyanogenic potential of Cycas seeds is documented in our cases. The gastrointestinal symptoms were severe enough that most patients sought medical attention but recovery was quick and complete.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Cyanides / blood
  • Cycas / poisoning*
  • Female
  • Glycosides / chemistry
  • Glycosides / poisoning
  • Humans
  • Hydrogen Cyanide / chemistry
  • Male
  • Middle Aged
  • Poison Control Centers
  • Poisoning / blood
  • Poisoning / physiopathology*
  • Poisoning / therapy
  • Retrospective Studies
  • Seeds*
  • Taiwan
  • Thiocyanates / blood


  • Cyanides
  • Glycosides
  • Thiocyanates
  • Hydrogen Cyanide
  • thiocyanate