evidence: People have used vitamin B17 as a cancer treatment since the 1800s, either alone or as part of a program of treatments. However, clinical trials on animals and humans have found [...] Vitamin B17, also known as amygdalin and laetrile, is not actually a vitamin. Instead, it is a drug derived from plant substances. People may consider using vitamin B17 to treat cancer, but no evidence supports it as an effective treatment and actually highlights the potentially severe adverse effects of its use. No human studies suggest any benefit of vitamin B17 as a cancer treatment, noting that it can cause cyanide poisoning, especially if a person takes it orally in tablet form. Cyanide poisoning can lead to mild-to-severe side effects and could even be fatal.