Is there a correlation between vitamin B17 (amygdalin/laetrile) and cancer?

Vitamin B17 (Amygdalin/Laetrile) and Cancer: No Proven Benefit, Significant Risk

There is no credible evidence that vitamin B17 (amygdalin/laetrile) provides any anticancer benefit, and its use carries a considerable risk of serious cyanide poisoning—you should strongly advise patients against using this substance for cancer treatment or prevention.

The Evidence Against Vitamin B17

The most definitive evidence comes from a Cochrane systematic review that evaluated all available data on laetrile/amygdalin for cancer treatment 1. Despite examining over 200 references, not a single randomized controlled trial or quasi-RCT met inclusion criteria for demonstrating efficacy. The review's conclusion is unambiguous: claims of beneficial effects are not supported by sound clinical data, and the risk-benefit balance is "unambiguously negative" 1.

Clinical Trial Data

The two clinical studies that actually tested amygdalin in cancer patients (conducted approximately 40 years ago) found no therapeutic benefit in 178 cancer patients who received the compound either orally or intravenously 2. These remain the only formal clinical trials, and both were negative.

The Toxicity Problem

Amygdalin is metabolized in the human body into hydrogen cyanide, which is the purported "active" component 3, 2. This creates an inherent and dangerous toxicity profile:

• The New South Wales Poisons Information Centre received 120 exposure calls between 2015-2022, with 32% requiring hospital referral or already involving hospitalized patients 4
• The FDA has not approved amygdalin/laetrile due to safety concerns related to cyanide poisoning 3
• Multiple case reports document serious adverse effects from cyanide toxicity, particularly after oral ingestion 1

Critical Pitfall to Avoid

Oral ingestion carries especially high risk because intestinal β-glucosidase enzymes activate the compound and release hydrogen cyanide 3. Patients may not realize that "natural" or "vitamin" labeling does not equate to safety.

The Disconnect Between Laboratory and Clinical Reality

While recent in vitro studies show that amygdalin can affect cancer cell lines through various mechanisms (apoptosis induction, cell cycle arrest, effects on COX-2 and nitric oxide synthase) 5, 2, 6, this laboratory activity has not translated to clinical benefit:

• In vivo animal studies show no or low treatment efficiency 2
• The gap between petri dish results and human outcomes is vast and unbridged
• Case reports describing anti-tumor effects exist but have never been confirmed in controlled clinical trials 2

Why Patients Seek This Treatment

Despite the lack of evidence and known toxicity, amygdalin emerged as an alternative therapy in the 1970s and continues to attract patient interest 3. Understanding this helps frame your counseling:

• Patients are often desperate for additional treatment options
• Marketing as "vitamin B17" creates a false sense of safety and legitimacy
• Online availability makes access easy despite regulatory restrictions
• Up to 68% of physicians are unaware when their cancer patients use supplements 7, creating a communication gap

Your Clinical Approach

When a patient asks about or discloses vitamin B17 use:

1. Directly state there is no evidence it works against cancer and it can cause cyanide poisoning
2. Quantify the risk: Explain that 32% of poison center calls required hospital-level care 4
3. Address the underlying need: Explore what the patient hopes to achieve (symptom control, disease modification, sense of control)
4. Redirect to evidence-based options: The National Cancer Institute strongly urges cancer patients to avoid vitamin and mineral supplements during treatment or use them only under physician guidance 7

Document the Discussion

Given the toxicity risk and prevalence of use, explicitly document that you counseled against vitamin B17 use and explained the cyanide poisoning risk. This protects both the patient and your practice.

Future Research Considerations

Nanoparticle formulations are being investigated to potentially reduce toxicity while maintaining any theoretical anticancer effects 5, 8, but this remains entirely experimental. These theoretical future developments should not influence current clinical recommendations—the compound remains dangerous and ineffective as currently available.

The evidence is clear: vitamin B17 has no place in cancer treatment or prevention outside of controlled research settings, and patients should be actively counseled against its use due to serious safety concerns without any demonstrated benefit to mortality, morbidity, or quality of life.