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Laetrile / Amygdalin (Vitamin B17)
Also known as: Laetrile, Amygdalin, Vitamin B17, Apricot Kernels, Apricot Seed Oil, Nitriloside
Amygdalin is a naturally occurring cyanogenic glycoside found in the seeds of stone fruits — apricots, bitter almonds, peaches, plums, and apple seeds. Laetrile is a semi-synthetic, patented derivative of amygdalin. In the 1950s, Ernst Krebs Sr. and Jr. promoted amygdalin as 'Vitamin B17' (it is not a vitamin). It was widely promoted as a cancer cure in Mexico and became hugely popular in the 1970s when thousands of American cancer patients travelled to Mexican clinics. It is still available in Mexico and some other countries where it is sold as 'amigdalina' injections.
What Proponents Claim
Krebs and modern proponents claim cancer cells uniquely contain an enzyme (beta-glucosidase) that cleaves amygdalin, releasing cyanide specifically inside cancer cells — killing them selectively. Healthy cells, they claim, contain a protective enzyme (rhodanese) that detoxifies any released cyanide. They assert it is 'Vitamin B17' and that deficiency causes cancer, and that modern diet's lack of bitter almonds and apricot seeds explains rising cancer rates.
What the Science Actually Shows
Verdict: Potentially Dangerous
The core claim — that beta-glucosidase is uniquely or predominantly in cancer cells — is false. Beta-glucosidase is present throughout the body, including in gut bacteria, intestinal cells, and many normal tissues. Rhodanese (the supposed 'protective' enzyme) is present in cancer cells too. The National Cancer Institute conducted a retrospective analysis of laetrile case reports in the 1970s and found no evidence of anti-cancer activity. Subsequently, the NCI ran the only prospective clinical trial of amygdalin in cancer patients (1982) — no tumour responses were observed and several patients developed cyanide toxicity. Multiple systematic reviews have found no reliable evidence of anti-cancer efficacy. The dangerous reality is that amygdalin does metabolise to cyanide — in both cancer and normal cells — and cyanide poisoning from laetrile/amygdalin is well-documented.
Regulatory Stance
The FDA banned laetrile in 1980 after NCI clinical trials showed no efficacy and documented toxicity. It is illegal to sell laetrile as a cancer treatment in the USA. The Supreme Court upheld the FDA ban in 1979 (US v. Rutherford). Despite the ban, laetrile continues to be available in Mexico, Germany, and several other countries. Many US patients travel to Tijuana clinics for laetrile injections. The European Food Safety Authority has warned against consumption of bitter apricot kernels due to cyanide content — a warning specifically prompted by rising sales of 'Vitamin B17' apricot kernels.
Known Risks
- Cyanide poisoning: amygdalin is metabolised to hydrogen cyanide — symptoms include headache, dizziness, nausea, vomiting, low blood pressure, and potentially fatal cardiovascular collapse
- Vitamin C dramatically increases cyanide release from amygdalin — patients taking high-dose vitamin C supplements alongside laetrile are at significantly elevated risk
- Deaths documented: multiple fatalities from cyanide poisoning following laetrile ingestion reported in medical literature
- Intravenous amygdalin: higher cyanide bioavailability and faster-onset toxicity than oral route
- Bitter apricot kernels: multiple children have been hospitalised after eating apricot kernels sold as health supplements
- Gut bacteria enhance cyanide release from oral amygdalin
- Delay of proven cancer treatment: the primary harm — patients who travel to Mexico for laetrile therapy often forgo curative-intent conventional treatment
- Financial harm: substantial cost of travel, accommodation, and injections at Mexican clinics
Research & Regulatory References
iOnco does not endorse, recommend, or discourage any specific treatment decision. This information is for educational purposes only. If you are a cancer patient, please make treatment decisions in consultation with your oncologist and care team. Evidence-based conventional treatment should not be delayed or foregone based on information on this page.