What Is "Vitamin B17"?
The name is a marketing construct. Here's what the compound actually is and where the name came from.
Amygdalin — The Natural Form
A cyanogenic glycoside found naturally in the seeds (kernels) of apricots, bitter almonds, apples, peaches, and cherries. First isolated in 1830 by chemists Robiquet and Boutron-Charlard. Plants use it as a defense mechanism; when the seed is crushed or digested, enzymes release hydrogen cyanide — which deters pests.
Laetrile — The Semi-Synthetic Form
A patented semi-synthetic derivative of amygdalin developed by Ernst T. Krebs Jr. in the 1950s. Chemically distinct from pure amygdalin but similarly releases cyanide upon hydrolysis. Marketed as a cancer treatment under various brand names. The terms "laetrile" and "amygdalin" are often used interchangeably by the media but refer to different molecular structures.
"Vitamin B17" — A Marketing Term
The "vitamin" label was coined by Krebs Jr. as a commercial strategy, not a scientific classification. Amygdalin is not a vitamin by any accepted definition: no human deficiency state exists, the body does not require it, and no nutritional authority — including WHO, FDA, or EFSA — recognizes it as a vitamin. The B17 designation was designed to imply essentiality and safety that the evidence does not support.
Chemical Classification
Amygdalin is formally classified as a cyanogenic glycoside with the molecular formula C₂₀H₂₇NO₁₁. On hydrolysis (by beta-glucosidase, stomach acid, or gut microbiota), it breaks down into: glucose, benzaldehyde, and hydrogen cyanide (HCN). The cyanide is the biologically active — and toxic — component. There is no form of amygdalin that circumvents this chemistry.
The Claimed Mechanism vs. What Science Found
Proponents proposed a "selective" anti-cancer mechanism. Here's the theory — and why the evidence doesn't support it.
The Proposed Theory
Krebs Jr. theorized that cancer cells express elevated levels of beta-glucosidase — the enzyme that cleaves amygdalin into HCN. The idea: cancer cells would selectively absorb amygdalin, cleave it into cyanide, and self-destruct. Normal cells were proposed to be protected by rhodanese (an enzyme that detoxifies HCN). This is the "selective toxicity" hypothesis.
Why the Theory Failed
The selective toxicity model was never validated in rigorous human trials. Beta-glucosidase is found throughout the gut microbiome, not uniquely in cancer cells. Rhodanese is present in both healthy and cancerous tissues in similar concentrations. HCN released systemically does not discriminate between cell types — it inhibits cytochrome c oxidase in all cells, disrupting cellular respiration universally. The selectivity claimed was not observed.
What In Vitro Data Shows
Chang et al. (2006) and similar studies do show cytotoxic effects in cancer cell lines in controlled lab settings. However, cytotoxicity in a petri dish does not equal selective anti-cancer activity in a living organism. Bleach is also cytotoxic in vitro. The question is whether the concentration that kills cancer cells in isolation can be safely delivered to a human — and the clinical data says it cannot.
The Evidence Gap
The critical gap between in vitro cytotoxicity and in vivo clinical benefit is where laetrile research collapsed entirely. No dose that produced anti-tumor effects in animal or cell studies could be administered to humans without causing systemic cyanide poisoning. This "therapeutic window" — the gap between effective and toxic doses — essentially does not exist in a usable form for amygdalin.
What the Studies Actually Found
A chronological review of the key human evidence — from the pivotal NEJM trial to the definitive Cochrane Review.
Moertel et al. (1982) — The Definitive Clinical Trial
The most rigorous human trial of laetrile ever conducted, published in the New England Journal of Medicine. 178 cancer patients with a variety of advanced cancers were treated with laetrile plus a metabolic therapy program (vitamins, pancreatic enzymes, diet). The researchers were led by Charles Moertel of the Mayo Clinic — one of the era's most respected oncologists.
Milazzo et al. (2015) — Cochrane Collaboration Review
The gold standard of evidence synthesis. Milazzo and colleagues systematically searched all available databases for randomized controlled trials and controlled clinical trials investigating laetrile or amygdalin for cancer. The review methodology was pre-registered and independent.
Chang et al. (2006) — In Vitro Cytotoxicity
Investigated the effects of amygdalin on bladder cancer cell lines in controlled laboratory conditions. Found cytotoxic effects at certain concentrations. This study is frequently cited by proponents as evidence of anti-cancer activity.
EFSA (2016) — Apricot Kernel Consumer Safety Opinion
The European Food Safety Authority conducted a formal risk assessment on bitter apricot kernels sold as food products, in response to growing popularity. The assessment modeled HCN release from realistic consumption scenarios.
The FDA Ban: A Timeline
The regulatory history of laetrile is long, contested, and ultimately resolved in favor of the ban. Here's how it unfolded.
Early Promotion
Amygdalin was used sporadically as a cancer remedy in Europe and the US. Ernst T. Krebs Jr. develops and patents "laetrile" in the 1950s, marketing it as Vitamin B17 and claiming it is non-toxic and selectively anti-cancerous. No supporting clinical data existed.
First FDA Action
The FDA declares laetrile a "new drug" requiring proof of safety and efficacy before sale. Manufacturers had no data to submit. Interstate shipment is blocked, though individual states began passing laws to permit its use within state lines.
Peak Popularity & Legal Battles
Laetrile reaches peak popularity — an estimated 70,000 Americans per year are using it. 27 states legalize it for in-state use. Proponents argue it is a "natural" substance and a matter of personal freedom. Court battles proliferate as patients seek access through emergency injunctions.
U.S. Supreme Court Rules
United States v. Rutherford: The Supreme Court unanimously rules that terminally ill patients do not have a constitutional right to unapproved cancer treatments. The FDA's authority to regulate laetrile is upheld. This eliminates the primary legal avenue used to circumvent the ban.
Federal Ban Formalized
Following the Rutherford ruling and in the absence of any clinical evidence of efficacy, the FDA formally bans the interstate sale of laetrile. State laws permitting intrastate use become largely moot as supply chains are cut. The ban remains in effect today.
NEJM Trial Closes the Chapter
Moertel et al. publish the definitive Phase II trial results. No benefit. Documented toxicity. The scientific case for laetrile is effectively closed. Remaining proponents retreat to anecdotes and alternative media.
Ongoing Enforcement & "Medical Tourism"
Laetrile clinics continue to operate in Mexico and other countries, marketing to US patients. The FDA actively warns consumers and intercepts illegal imports. The compound is banned in Australia, UK, and throughout the EU as well. Deaths continue to be reported in medical literature.
Toxicity & Risk Profile
This is the most important section on this page. The safety data is unambiguous.
⚠️ Clinical Symptoms of Amygdalin/Cyanide Toxicity
Symptoms typically appear within 30–60 minutes of oral ingestion. Severity depends on dose, individual body weight, gut microbiome composition, and whether Vitamin C or vitamin B12 co-ingestion reduces/potentiates effects.
📊 Oral vs. Intravenous Risk Comparison
| Factor | Oral Route | Intravenous Route |
|---|---|---|
| HCN Release | Amplified by gut bacteria (beta-glucosidase) | Less enhancement from gut microbiome |
| Onset of Toxicity | 30–60 min (unpredictable) | More immediate, more predictable |
| Documented Fatal Cases | Multiple in literature | Fewer, but documented |
| Vitamin C Interaction | Increases HCN release | Also increases HCN release |
| Legal Status (US) | Illegal / FDA banned | Illegal / FDA banned |
🚨 Emergency Information
If you or someone you know has ingested bitter apricot kernels, amygdalin, or laetrile and is showing symptoms of poisoning, call emergency services immediately (911 in the US, 999 in UK, 112 in EU). Inform them of amygdalin/cyanide exposure. Time-critical antidotes (hydroxocobalamin, sodium nitrite/thiosulfate) are available in emergency settings. Do not attempt to induce vomiting without medical guidance.
Supporting Liver Function
Amygdalin toxicity causes documented liver enzyme elevation and hepatotoxicity. If you are researching alternative health approaches, these liver-support supplements have an actual evidence base.
Evidence-Based Liver Support Options
Unlike amygdalin, the following compounds have meaningful clinical or mechanistic evidence supporting liver health. These are not replacements for medical care.
Common Questions Answered
Straightforward answers to the questions we see most often.
Want the Complete Protocol Guide?
Dosing schedules, interaction warnings, and cycle protocols for 50+ compounds — all in one place.
Get the Guide →