Vitamin B17 is primarily used as an anti-cancer agent due to its cytotoxic properties. This vitamin is more commonly known as amygdalin and is extracted from the seed of the apricot fruit, according to WebMD.
When vitamin B17 enters the body, it is converted by the stomach into cyanide, which is a highly toxic chemical. Thus, if ingested in high enough amounts, vitamin B17 can have severe heath effects, including loss of breath, seizure, coma, cardiac arrest and death, according to Wikipedia. In cancer treatment, these toxic effects are used to reduce the proliferation of cancer cells, as cyanide kills off rogue cells at a lower dosage than would kill the patient.
Researchers had first hoped that vitamin B17 remains undigested in the patient's body and would only convert to cyanide within tumor cells. If this were so, vitamin B17 would have been a wonder drug, as its toxic effects would not harm the patient. However, this has proven to be false through various studies, according to WebMD. Cyanide prevents the utilization of oxygen by cells, described as histotoxic hypoxia. Cyanide prevents the action of the enzyme cytochrome c oxidase, which plays a critical role in the electron transport chain by using oxygen to produce water, according to Wikipedia.