Does Laetrile (Vitamin B17) Cure Cancer?

Often it is a bag of bitter apricot seeds; sometimes it is a bottle labeled "vitamin B17." A simple substance from fruit pits kills cancer cells and spares healthy ones, the pitch goes, and drug companies buried it because nobody can patent a seed. All you have to do is take it.

It is a good story, almost every part of it is wrong, and some of the wrong parts can hurt you.

Amygdalin is a real compound, found in the pits of apricots and peaches, in bitter almonds, and in other plants. Laetrile is a partly man-made version of it. The two names get used as though they mean the same thing, and in everyday conversation they mostly do.

The name "vitamin B17" was invented by a promoter, E.T. Krebs Jr. The committee that officially names vitamins never accepted it. The National Cancer Institute is blunt about this. There is no evidence that laetrile is needed for normal body chemistry, and no evidence that it acts as a vitamin in animals or in people.

Calling it a vitamin was marketing, not science, and that label did enormous work. A vitamin sounds both safe and necessary. A cyanide-releasing plant compound does not.

When amygdalin breaks down it releases hydrogen cyanide. This is ordinary chemistry, not rhetoric. An enzyme called beta-glucosidase splits the molecule into cyanide, benzaldehyde, and sugar.

The original theory was tidy. Tumors were said to be loaded with beta-glucosidase and short of rhodanese, the enzyme that clears cyanide, so the poison would fire inside the tumor and be mopped up everywhere else. It did not survive testing.

How you take it changes the danger considerably. Swallowed laetrile is far more likely to poison you, because bacteria in your gut carry the enzyme that frees the cyanide, while injected laetrile releases much less. Animal work shows this directly. Rats raised germ-free had no ill effects and normal blood cyanide, while ordinary rats given the same compound became sluggish and had seizures.

Some everyday foods make it worse. NCI specifically names raw almonds, certain fruits and vegetables, and high-dose vitamin C. In an early NCI study, two patients who ate raw almonds while taking laetrile by mouth developed signs of cyanide poisoning.

The reported harms are not minor. NCI's list runs from nausea, vomiting, headache and dizziness through dangerously low blood pressure, liver damage, nerve damage that makes walking difficult, fever, confusion, coma, and death.

This is the part the suppression story leaves out. Laetrile was not ignored; it was studied with public money, by the very agency accused of hiding it.

NCI ran animal studies across many tumor types. None of the solid tumors or leukemias responded at any dose tested, and survival did not improve in any treated group.

NCI then went looking at the testimonials themselves, reviewing 67 case reports from laetrile users. Two looked like complete responses and four showed tumors shrinking. That was thin, but it was not nothing, so NCI funded a human trial.

Charles Moertel and colleagues published it in 1982, using the routine laetrile practitioners actually followed: amygdalin by vein for 21 days, then pills, plus vitamins, pancreatic enzymes, and a set diet. There were 175 patients assessed, most with breast, colon, or lung cancer.

One patient had a partial response, and it lasted ten weeks. By the end of the intravenous course, 54 percent already had cancer that was measurably growing, and seven months after treatment ended every patient's cancer had grown. About one in five reported feeling better for a while, though for most that feeling did not hold. Blood cyanide levels rose during the oral phase.

That is not a buried result. That is a result.

The FDA has never approved laetrile for cancer. An application to study it as a new drug was accepted in 1970 and then rejected, court fights followed, and more than 20 states legalized it anyway. In 1980 the Supreme Court upheld the federal ban on shipping it between states. It cannot legally be sold in the UK or Europe either.

It never went away. Most of it is now manufactured in Mexico, outside FDA oversight, and that has consequences you cannot see in a capsule. Labels have been documented as wrong, and samples have been found contaminated with bacteria and other substances. You do not really know your dose, which matters enormously for something that releases a poison.

The FDA still acts against sellers. In 2021 it warned a company selling bitter apricot seeds, amygdalin extract and a product called Laetrile B17, over claims that B17 kills harmful cells and controls cancer.

Because the appeal is real, and it is not foolish.

Cancer strips away control, and laetrile hands some back. It is cheap, and you can buy it yourself today without anyone's permission. The story even explains why your doctor says no, which converts that "no" into proof rather than a warning. And it usually arrives from someone who is frightened for you and desperate to do something useful. That is not a bad motive.

Testimonials feel like evidence because they are about actual people, but a story cannot separate the remedy from everything else going on. Most people who take laetrile also had surgery, chemotherapy, or radiation; some cancers move slowly; a few behave strangely on their own. Trials exist precisely because a story cannot sort that out.

Cyanide poisoning is the obvious risk, and it is not the biggest one.

The biggest harm is time. Treatments that work often work best early, so weeks spent on apricot seeds are weeks a treatable cancer keeps growing. This harm is silent. Nobody feels it happening, and it shows up later, on a scan.

You can say that to a relative without starting a fight. Begin with "I know you are trying to help," then hand them something real to do — a ride, a meal, a seat beside you during infusion.

Three questions do most of the work.

Was it ever actually tested? Search the name plus "PDQ" at cancer.gov, where NCI keeps summaries on alternative cancer treatments, including the ones that failed.

Does the cover-up story survive a look at the dates? Laetrile's own history breaks it, because the agency accused of hiding the cure is the one that paid for the trial.

Who profits? FDA warning letters are public, so search the product name at fda.gov. The sentences quoted back at a company are often the exact ones that first convinced you.

If you are already taking it, tell your oncologist — not to ask permission. They need to know, because cyanide affects lab results and can interact with other things you take.

• Laetrile/Amygdalin (PDQ) Health Professional Version — National Cancer Institute
• Laetrile/Amygdalin (PDQ) Patient Version — National Cancer Institute
• Laetrile (amygdalin or vitamin B17) — Cancer Research UK
• Illegally Sold Cancer Treatments — US Food and Drug Administration
• Warning Letter: Richardson Nutritional Center — US Food and Drug Administration