Toxicity
The metabolism of amygdalin produces hydrogen cyanide, a potent toxin. Beta-glucosidase, one of the enzymes that catalyzes the release of cyanide from amygdalin, is present in the human small intestine and in a variety of common foods. This leads to an unpredictable and potentially lethal toxicity when amygdalin or laetrile is taken orally. Ingestion of purified amygdalin or apricot kernels can cause severe toxicity and death due to cyanide poisoning. Numerous case reports in medical literature describe serious cyanide poisoning in patients who ingested laetrile as a cancer treatment. Blood cyanide concentrations may be measured as a means of confirming the diagnosis in hospitalized patients or to assist in the forensic investigation of a fatal overdose.
Some laetrile promoters have claimed that the cyanide generated by laetrile is immediately harmlessly detoxified by the mitochondrial enzyme rhodanese into thiocyanate. However, these claims are false. First, because thiocynate is also toxic, although to a lesser degree. Second, the body only can use the small amount of rhodanese that is present in the blood, regardless of the stores present in kidneys and liver. Third, the limited factor in this conversion are the stores of cystine, cysteine, and other sulfur compounds, which are rapidly depleted in laetrile poisoning. Fourth, blood analysis show undetoxified cyanide in persons poisoned with laetrile or with apricot kernels.
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