This page tells you about laetrile (also known as amygdalin or vitamin B17) in people with cancer.  There is information on

What is laetrile?

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.  Some people call laetrile vitamin B17, although it isn’t a vitamin.  It also has the scientific names
  • Mandelonitrile beta-D-gentiobioside and   
  • Mandelonitrile-beta-glucuronide
Manufacturers of laetrile promote it as an alternative cancer treatment.  This means it is used instead of conventional cancer treatment.  The first use of laetrile as a treatment for cancer was in Russia in 1845, but it wasn’t used in the USA until the 1920s.  In the 1950s people began promoting laetrile as a ‘highly active compound’ that can cure cancer.  Unfortunately, this is simply not true – laetrile cannot cure cancer.  The supposed active ‘cancer killing’ ingredient in laetrile is cyanide. Cyanide, as you probably know, is highly poisonous.

Laetrile can cause serious side effects.  We don’t recommend that you replace your conventional cancer treatment with any type of alternative cancer therapy, such as laetrile.  Or that you use laetrile alongside your cancer treatment.


Why do people with cancer use laetrile?

People with cancer use alternative cancer therapies such as laetrile, for various reasons.  They may use it because
  There is no scientific evidence to support any of these reasons for using laetrile.


If your cancer can’t be cured

Your doctor may tell you that there are no further conventional cancer treatments available that could cure your cancer.  But treatments to control your symptoms are still possible.  The news that your cancer can’t be cured is very difficult to accept.  And in this situation, many people consider alternative therapies, including laetrile.

Controlling or curing your cancer

Some people promote alternative therapies such as laetrile to cure or treat cancer.   But there is no scientific evidence to prove that laetrile can do this.

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

The USA’s National Cancer Institute reviews the results of clinical research into the use of laetrile for cancer on its website.  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 studies when given with enzymes.  This is most probably because the enzymes cause the amygdalin to release cyanide, which killed the cancer cells grown in the lab.  One website promoting laetrile includes the quote "When we add laetrile to a cancer culture under the microscope, providing the enzyme glucosidase is also present, we can see the cancer cells dying off like flies."  This isn’t surprising, as the glucosidase makes the laetrile release cyanide, which is a poison.  The difficulty is getting the amygdalin close enough to cancer cells, along with the glucosidase, to cause it to kill them without poisoning surrounding normal tissues or the whole body.
This mirrors the main difficulty in a great deal of cancer research – as many cancer therapies are poisons.  As cancer develops initially from normal body cells, the only way to kill cancer cells would be to use treatments that are poisonous to human cells.  The mainstay of research today is how to get such treatments to the cancer cells without killing or damaging too many normal cells.  Or to develop treatments that are directed at the subtle differences between normal cells and cancer cells – in other words targeted treatments.

Another study claimed that amygdalin might make cancer cells more sensitive to radiation.  Doctors have known for a long time that cancer cells at the centre of tumours have less oxygen than cells nearer the outside of tumours.  This absence of oxygen makes the central cells more resistant to radiotherapy.  Apparently, during this study, amygdalin stopped cells in a laboratory dish from absorbing oxygen.  The researchers then wondered whether preventing the cells on the outside of a tumour from absorbing oxygen with amygdalin, would mean more oxygen getting to the cells in the centre.  But the problem remains of how to get the oxygen into the cells at the centre of the tumour.  A great deal of cancer research has been carried out for many years simply to try to find a way of doing this.  Since this research was first reported in 1978, it has not been confirmed by any other research.

There have only been two published human studies testing the efficacy of laetrile as a treatment for cancer.  They were both sponsored by the American National Cancer Institute in the late 1970s and early 1980s.  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 looked at whether laetrile had any effect on shrinking cancer tumours in 175 patients.  Of these patients, only one 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 randomised controlled clinical trials using laetrile.

A systematic review was published by the Cochrane Library in January 2006 which looked at laetrile treatment for cancer.  It concluded that the claimed benefits of laetrile are not supported by controlled clinical trials.  You can read a plain language summary of this review on the Cochrane website.

What taking laetrile involves

If you take laetrile, you have it
  • As an injection (intravenously)   
  • As tablets
Taking laetrile as tablets has more toxic 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 typically recommend you have daily intravenous injections for 2 and 3 weeks, followed by laetrile tablets for some time.  Laetrile is also used in enemas and lotions that you can apply to your skin. 

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 regime to stick to.

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   
  • Headache   
  • 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
If you do take laetrile as tablets, it is very important that you avoid eating
  • Raw almonds   
  • Crushed fruit stones or pips   
  • Celery   
  • Apricots   
  • Peaches   
  • Beansprouts   
  • Carrots   
  • High doses of vitamin C   
  • Beans  - mung, lima, butter and other pulses   
  • Flax seed   
  • Nuts
All these can increase the risk of cyanide poisoning if you take them with laetrile because they contain low levels of amygdalin.  (These foods are safe when you eat them without laetrile because the levels of amygdalin in them are low.)

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 in the US (FDA) have also banned it.

But some hospitals and clinics in Mexico offer laetrile.  And there are many websites that promote its use.  These websites often encourage people with cancer to travel to the Mexican clinics for treatment.  As well as the considerable cost of the treatment, you also have to come up with money for your airfares and accommodation when you are there. 

Our advice is to be careful if you read any websites that promote the use of laetrile and recommend treatment in overseas clinics.  You may find it useful to read the following information in our about complementary and alternative therapy section on

A word of caution

At the end of the day, only you can decide whether or not to use alternative cancer therapies such as laetrile.  But we don't recommend using any alternative therapies, including laetrile, in place of conventional treatment.  There is often little (if any) scientific or medical evidence to back up the claims made by their promoters.  If you have cancer, using unproven methods instead of conventional medical treatment can seriously affect 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.

Whenever we put up information on alternative treatments that have not been properly tested, we receive angry emails that say we are trying to prevent people with cancer from getting effective treatment. This is not what we want to do.  We are concerned that products are marketed as potential cures, and often sold for a great deal of money, when they lack scientific evidence to prove they help.  It is not in the interests of drug companies or research organisations such as ours to ignore potential new treatments.  Thousands and thousands of compounds are screened every year to try to find those that might be the basis of effective treatments.  If laetrile or amygdalin had any therapeutic benefit, drug companies would have developed it into a potential treatment long ago.

It is understandable that you and your loved ones will want to try anything if you think it might help treat or cure your cancer.  So our message is
  • Be careful   
  • Make sure you look into all the information that is 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.  The complementary therapy organisations and complementary therapy websites may be able to offer more information about laetrile.  There is detailed information on the CAM-cancer website.