evidence: ALSO KNOWN AS: Laetrile, "vitamin B17," mandelonitrile-beta-glucuronide (semisynthetic), mandelonitrile beta-D-gentiobioside (natural product), laevorotatory and mandelonitrile, prunasin. [...] RESEARCH: Amygdalin is metabolized by the enzyme betaglucosidase into benzaldehyde, glucose, and cyanide.[1] Claims of its anticancer activity rely on the theory, now proven false, that cancer cells contain elevated amounts of the betaglucosidase compared to normal cells. The cyanide resulting from the hydrolysis of amygdalin is believed to be cytotoxic.[2] It was further postulated that normal cells convert the cyanide to benign thiocyanate. However, there is no convincing evidence for this selective effect on neoplastic cells. It has also been claimed by some promoters that amygdalin is a vitamin (B17) and that cancer develops due to deficiencies in B17, but no data substantiate this idea. Laboratory studies suggest that amygdalin has anticancer properties,[3] but a 1982 clinical trial conducted by the National Cancer Institute failed to find any effectiveness. Moreover, several study patients had symptoms of mild cyanide toxicity or significant levels of cyanide.[4] A systematic review of 36 case series and case reports concluded that amygdalin is ineffective.[5]