Supplement analysis backed by scientific evidence · PT

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Limited evidenceGeneral health

Vitamin B17 (Laetrile/Amygdalin)

Laetrile is not a vitamin and does not treat cancer. Every controlled evaluation, including a Cochrane review and a large NCI-sponsored clinical trial, found no anticancer benefit and documented cyanide toxicity — including deaths. Do not take it.

What the science says

  • Treats or cures cancer Limited evidence

    A Cochrane systematic review found no randomized controlled trial showing any benefit of laetrile or amygdalin in cancer, and concluded the risk-benefit balance is unambiguously unfavorable. In the NCI-sponsored clinical trial of 178 patients treated with amygdalin plus a metabolic therapy regimen, no substantive tumor response was seen, disease progressed in essentially all patients within months, and several developed blood cyanide levels approaching the lethal range.

  • B17 is a vitamin whose deficiency causes cancer Limited evidence

    Amygdalin is a plant cyanogenic glycoside found in apricot and bitter almond kernels. It has no known human requirement, no deficiency syndrome, and no vitamin function. The 'vitamin B17' name was coined promotionally in the 1950s and has never been recognized by any nutrition authority.

  • Selectively kills cancer cells because tumors lack rhodanese Limited evidence

    The proposed mechanism — that beta-glucosidase in tumors releases cyanide while healthy tissue detoxifies it — does not hold up: human tumors do not reliably express more beta-glucosidase, and the enzyme most responsible for releasing cyanide from amygdalin is gut bacterial, which is why oral dosing is far more toxic than intravenous. That detail explains the poisonings rather than any selectivity.

Dosage & safety

Studied doseNo safe or effective dose exists and none should be sought. For context on the toxicity: historical regimens used 500 mg oral tablets several times daily or intravenous infusions of 4.5–9 g, and the severe poisonings reported in the literature involved oral amygdalin plus apricot kernels. Bitter apricot kernels contain roughly 0.5–3 mg of cyanide-equivalent each; European food safety guidance warns that a small handful can exceed acute reference doses in adults, and far fewer in children.
SafetyAmygdalin releases hydrogen cyanide when metabolized by gut bacteria. Documented effects include headache, nausea, vomiting, dizziness, bluish skin, liver damage, drop in blood pressure, coma and death; a published case describes severe cyanide poisoning in a 4-year-old given amygdalin and apricot kernels as an alternative treatment. Risk rises sharply with oral dosing, with concurrent high-dose vitamin C (which increases cyanide release), and with raw almonds, crushed fruit kernels or other beta-glucosidase-containing foods. Laetrile is not approved by the FDA, cannot be legally sold or imported into the US for cancer treatment, and is banned or restricted in the EU and Australia. The most serious harm is often indirect: patients who choose it in place of effective oncology treatment lose the window in which their cancer was treatable.

Scientific references

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