Laetrile (amygdalin, vitamin B17) | Cancer Research UK
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What laetrile is

Laetrile is a partly man made (synthetic) form of the natural substance amygdalin. 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. 

Some people call laetrile vitamin B17, although it isn’t a vitamin. It also has the names

  • Mandelonitrile beta D gentiobioside
  • Mandelonitrile beta glucuronide
  • Laevorotatory
  • Purasin
  • Amygdalina
  • Nitriloside

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. Alternative treatment means that people use it instead of conventional cancer treatments such as cancer drugs or radiotherapy. The first 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. We review the research into laetrile below. 

We recommend that you don't replace your conventional cancer treatment with any type of alternative cancer therapy, such as laetrile. Laetrile can cause serious side effects in some people so we don't recommend that you use laetrile alongside your cancer treatment.


Why people with cancer use laetrile

Although there is no evidence that laetrile can help with cancer, some people take it because they believe it might

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

Some people want to use laetrile if they are told that their cancer can't be cured with conventional cancer treatments. They hope that laetrile will be able to control or cure their cancer. There is no scientific evidence to support any of these reasons for using laetrile.


What taking laetrile involves

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.


Research into laetrile as a cancer treatment

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.

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.

You can read more information about research into laetrile on the CAM-CANCER website.


Side effects of laetrile

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

  • Sickness
  • 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 cost of laetrile

Because of the lack of evidence that laetrile works, and the serious side effects it has, it is not authorised for sale in the European Union. The Food and Drugs Agency (FDA) in the USA have also banned it. An American website estimated the cost of laetrile injections for 21 days to start the treatment at about $336. Then it costs about $160 a month for laetrile tablets.

Some hospitals and clinics in Mexico offer laetrile. They may use a different type of laetrile than the one available from websites. Some websites encourage people with cancer to travel to the Mexican clinics for treatment. Treatment at the clinics may cost thousands of pounds and you also have to pay for your airfares and for your accommodation when you are there.

Our advice is to be careful if you read any websites that promote the use of laetrile or recommend treatment in overseas clinics.


A word of caution

Only you can decide whether or not to use alternative cancer therapies such as laetrile. But we recommend that you don't use any alternative therapies, including laetrile, instead of conventional treatment. If you have cancer, using unproven methods instead of conventional medical treatment can seriously harm your health.

Many internet sites advertise and promote laetrile as a treatment to cure cancer. But no reputable scientific cancer organisations support any of these claims. Our advice is to be very cautious about believing this type of information or paying for any alternative cancer therapy over the internet.

We are concerned that products are marketed as potential cures. They are often sold for a great deal of money, when they lack scientific evidence to prove that they help. And they could also cause harm. 

It is understandable that you and the people close to you will want to try anything if you think it might help treat or cure your cancer. So our message is to

  • Be very careful
  • Make sure that you look into all the information available, and check who provides it
  • Talk to your cancer doctor before you spend money for any therapy, whether it’s conventional, complementary or alternative

Where to find more information

Our section about complementary and alternative therapies is a useful place to start for general information about complementary and alternative therapies in cancer care. 

You may find it useful to read the following information about

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Updated: 30 January 2015