evidence: The third theory suggests that cancer is caused by a deficiency in vitamin B17 (amygdalin). [...] Laetrile is often wrongly called vitamin B17. It is actually a patented drug that was invented by Dr. Ernst T. Krebs, Jr. in 1952. [...] He likely labeled laetrile as vitamin B17 so that it would be classified as a nutritional supplement, rather than a medicine. This is likely because the tough federal laws that apply to marketing drugs do not apply to supplements.