Laetrile is a partly man made (synthetic) form of the natural substance Amygdalin and has been used as a treatment for people with cancer worldwide. The term “laetrile” comes from 2 words (laevorotatory and mandelonitrile) and is used to describe a purified form of the chemical amygdalin. Amygdalin is a plant compound that contains sugar and produces cyanide. Cyanide is believed to be the active cancer-killing ingredient in laetrile.

Amygdalin is a plant substance found naturally in raw nuts and the pips of many fruits, particularly apricot pips, or kernels. It is also present in plants such as lima beans, clover and sorghum.

Although laetrile is also often called Vitamin B17, it isn’t a vitamin. It is also known as Mandelonitrile beta D gentiobioside; Mandelonitrile beta glucuronide; Laevorotatory; Purasin; Amygdalina, and Nitriloside.

A History of the Medical Use of Laetrile/ Amygdalin

The first known use of laetrile as a treatment for cancer was in Russia in 1845, and it was used in the USA from the 1920s.

In the 1970s, laetrile was widely promoted as an anti-cancer agent either on its own or as part of a programme with a particular diet, high dose vitamin supplements, and pancreatic enzymes.

The early pill form of amygdalin was found to be too toxic, and work with the compound was stopped.

In the 1950s, a reportedly nontoxic, partly synthetic form of amygdalin was made and patented in the United States as Laetrile.

Laetrile gained popularity in the 1970s as a single anticancer agent and as part of a metabolic therapy program that included a special diet, high-dose vitamin supplements, and pancreatic enzymes (a group of proteins that aid in the digestion of food).

By 1978, more than 70,000 people in the United States had reportedly been treated with Laetrile.

In 1980, the U.S. Supreme Court upheld a ban on the shipment of laetrile between states in the United States. It is still used in Mexico and at some clinics in the United States.

Laetrile/ Amygdalin as an Alternative Therapy

There is no scientific evidence to support claims that laetrile or amygdalin can treat cancer or any other illness. Despite this it has been promoted as an alternative cancer treatment. Some individuals take Laetrile/ Amygdalin because they believe it might

  • Improve their health, energy levels and wellbeing
  • Detoxify and cleanse the body
  • Help them to live longer

Cyanide is thought to be the main anti-cancer ingredient in laetrile. Two other breakdown products of amygdalin, prunasin (which is similar in structure to Laetrile) and benzaldehyde, may also be cancer cell blockers.

The following theories have been proposed to support the use of laetrile for cancer:

Amygdalin nuts

Two of the theories state that the balance of certain enzymes in cancer cells allows laetrile to be toxic to the cancer cells. There is some evidence that normal tissues and malignant tissues do have different amounts of these enzymes.

Another theory states that cancer is the result of a vitamin deficiency and that laetrile, or “vitamin B-17,” is the missing vitamin needed by the body to restore health. There is currently no evidence that laetrile is needed by the body or that laetrile can act as a vitamin in animals or humans.

The fourth theory states that the cyanide released by laetrile has a toxic effect that results in killing the cancer cells and stopping them from growing. The theory also states that the damage to the cells causes a boost to the immune system.


Most of the websites or magazines promoting laetrile base their claims on unsupported opinions and anecdotal evidence. There isn’t any evidence that laetrile is an effective treatment for cancer or any other illness.

One animal study claimed that amygdalin slowed the growth of cancer in animals and helped stop tumours spreading to the lungs. But repeated studies couldn’t show similar results, so the treatment remains unproven.

Amygdalin (the active ingredient in laetrile) has shown anti cancer activity in two laboratory studies when given with particular enzymes called glucosidase. This is probably because the enzymes made the amygdalin release cyanide which killed the cancer cells grown in the lab. But in the body the cyanide would also damage healthy cells.

Another study claimed that amygdalin might make cancer cells more sensitive to radiation. Cancer cells at the centre of tumours have less oxygen than cells nearer the outside of tumours. Lack of oxygen makes the central cells more resistant to radiotherapy. Apparently, during one study, amygdalin made cells in a laboratory dish absorb more oxygen. Since this research was first reported in 1978, it has not been confirmed by any other research.

Amygdalin peaches

The USA’s National Cancer Institute (NCI) reviews the research into the use of laetrile for cancer in humans on its website. Two published studies were sponsored by the NCI in the late 1970s and early 1980s. The studies tested whether laetrile works as a treatment for cancer in humans.

The first study was a phase I clinical trial looking at safe levels of laetrile, and involved only 6 patients. It tested the dosage and different ways of giving laetrile. Although the researchers reported very few side effects, 2 patients developed symptoms of cyanide poisoning because they ate raw almonds while taking amygdalin.

The second study in 1982 looked at whether laetrile could shrink cancer tumours in 175 patients. Of these patients, only 1 person had any apparent response to laetrile and this only lasted for 10 weeks. Seven months after the study, all the patients’ cancers had continued to grow. There haven’t been any large well designed clinical trials using laetrile.

The Cochrane Library published a systematic review in 2011 which looked at laetrile treatment for cancer. It stated that the claimed benefits of laetrile are not supported by controlled clinical trials. It also found that there is a risk of serious adverse effects from cyanide poisoning after laetrile or amygdalin, especially after taking it by mouth. You can read a summary of the Cochrane review about laetrile on the Cochrane website.

How is Laetrile/ Amygdalin Administered?

Laetrile is given by mouth (orally) as a pill. It can also be given by injection into a vein (intravenously) or muscle. Laetrile is commonly given intravenously over a period of time and then orally as maintenance therapy (treatment given to help extend the benefit of previous therapy).

Amigdalin Solucion Injectable-Big

Laetrile is available

  • As an injection (intravenously)
  • As tablets
  • As skin lotions
  • As a liquid to put into the back passage (rectum)

Taking laetrile as tablets has more side effects than having it as an injection.

Our digestive bacteria, and the enzymes in the food we eat, break down the laetrile and release cyanide.

Laetrile’s promoters usually recommend that you have daily injections into a vein for 2 or 3 weeks, followed by laetrile tablets for some time.

Laetrile is also used in lotions to apply to your skin. It is used in enemas that are inserted into the back passage (rectum).

People who promote laetrile usually also suggest that you also

  • Take high doses of vitamins
  • Follow a special diet

So it can be quite a rigid and complex treatment to stick to.

Side Effects or Risks

Laetrile can cause serious side effects in some people so we don’t recommend that you use laetrile alongside your cancer treatment.

Laetrile contains cyanide, which is a type of poison. So the side effects of laetrile are the same as those of cyanide. These include

  • Nausea and vomiting
  • Headaches
  • Dizziness
  • Liver damage
  • A lack of oxygen to the body tissues
  • A drop in blood pressure
  • Drooping eyelids
  • Fever
  • Nerve damage, causing loss of balance and difficulty walking
  • Confusion, coma and eventually death

It is estimated that eating approximately 50 to 60 apricot kernels, or 50g of laetrile, can cause death.

If you take laetrile as tablets, it is very important that you avoid eating other foods that contain amygdalin such as

  • Raw almonds
  • Crushed fruit stones or pips
  • Celery
  • Apricots
  • Peaches
  • Bean sprouts
  • Carrots
  • High doses of vitamin C
  • Beans – mung, lima, butter and other pulses
  • Flax seed
  • Nuts

These foods are safe when you eat them without laetrile because the levels of amygdalin in them are low. It is also important for anyone with liver problems to know that laetrile may cause further damage to their liver.

The side effects of laetrile appear to depend on the way it is given. Side effects are more severe when laetrile is given by mouth than when it is given by injection. These side effects may be increased by:

  1. Eating raw almonds or crushed fruit pits.
  2. Eating certain types of fruits and vegetables, including celery, peaches, bean sprouts, and carrots.
  3. Taking high doses of vitamin C.


Please note that the Little Fighters Cancer Trust shares information regarding various types of cancer treatments on this blog merely for informational use.

LFCT does not endorse or promote any specific cancer treatments – we believe that the public should be informed but that the option is theirs to take as to what treatments are to be used.

Always consult your medical practitioner prior to taking any other medication, natural or otherwise.