Laetrile (amygdalin or vitamin B17)

Laetrile is promoted as an alternative cancer treatment. There is not enough reliable evidence that it works.


  • Laetrile is a man-made form of amygdalin, a plant substance found in some nuts, plants and seeds of fruit.
  • Claims that laetrile or amygdalin can treat cancer are not backed up by research.
  • It contains cyanide, a poison and can cause serious side effects.

What laetrile is

Laetrile is a partly man-made (synthetic) form of the natural substance amygdalin. Amygdalin is a plant substance found in raw nuts, bitter almonds, as well as apricot and cherry seeds. Plants like lima beans, clover and sorghum also contain amygdalin.

Some people call laetrile vitamin B17, although it isn’t a vitamin. 

Why people with cancer use it

Laetrile has been used as an anti cancer agent since the 1800’s. It is used either on its own or as part of a programme. This might include following a particular diet, high dose vitamin supplements and pancreatic enzymes.

When laetrile is processed by the body, it changes to cyanide. Cyanide is a type of poison which is thought to kill cancer cells. There is not enough reliable scientific evidence to say laetrile can treat cancer. 

People who use laetrile believe it might:

  • improve their health, energy levels and wellbeing
  • detoxify and cleanse the body
  • help them to live longer

How you have it

Laetrile is available as:

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

Taking laetrile as tablets has more side effects than having it as an injection. This is because our digestive system breaks down the laetrile and releases cyanide. Cyanide is a type of poison.

Side effects

Laetrile contains cyanide. So the side effects of laetrile are the same as those of cyanide. These include:

  • fever
  • sickness
  • headaches
  • dizziness
  • liver damage
  • drooping eyelids
  • a lack of oxygen to the body tissues
  • a drop in blood pressure
  • nerve damage, causing loss of balance and difficulty walking
  • confusion, coma and eventually death

Avoid eating other foods containing amygdalin if you take laetrile as tablets. This may include foods like:

  • raw almonds
  • carrots
  • celery
  • apricots
  • peaches
  • bean sprouts
  • beans – mung, lima, butter and other pulses
  • nuts
  • flax seed
  • high doses of vitamin C
  • crushed fruit stones or pips

These foods are safe to eat when you’re not taking laetrile because the levels of amygdalin in them are low.

Laetrile may cause further damage to your liver if you have liver problems.

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 scientific evidence that laetrile is an effective treatment for cancer or any other illness.

The Cochrane Library published a systematic review in 2015. This means that a group of experts gather all the evidence about a particular subject and go through it to work out whether there is any evidence to support it.

This review said that the claimed benefits of laetrile are not supported by controlled clinical trials. It also found a risk of serious side effects from cyanide poisoning after laetrile or amygdalin, especially after taking it by mouth.

How much it costs

No one can sell laetrile in the UK or Europe. There is not enough reliable scientific evidence that it works. It also has serious side effects and is banned in the USA by the Food and Drugs Agency (FDA).

A word of caution

It is understandable that you might want to try anything if you think it might help treat or cure your cancer. Only you can decide whether to use an alternative cancer therapy such as laetrile.

You could harm your health if you stop your cancer treatment for an unproven treatment.

Many websites promote laetrile as a cure for cancer. But no reputable scientific cancer organisations support any of these claims. Be cautious about believing this type of information or paying for any alternative cancer therapy over the internet.

  • Laetrile treatment for cancer
    S Milazzo and others
    Cochrane Database of Systematic Reviews 2015, Issue 4.

  • Cyanide and lactate levels in patients during chronic oral amygdalin intake followed by intravenous amygdalin administration
    J. Mani and others
    Complementary therapies in medicine, 2019. Volume 43, Pages 295-299

  • Toxic phytochemicals and their potential risks for human cancer
    Cancer Prevention Research (Philadelphia). 2015, Volume 8, Issue 1, Pages 1–8.
    Ann M. Bode and Zigang Dong

  • CAM-Cancer website
    Accessed September 2022

  • Recent updates and future perspectives about amygdalin as a potential anticancer agent: A review
    J. Shi and others
    Cancer Medicine, 2019. Volume 8, Issue 6, Pages 3004-3011

  • Advanced research on anti-tumor effects of amygdalin
    Journal of Cancer Research and Therapeutics. 2014, Vol 10, Issue 1, Pages 3-7.
    Z Song Z and X Xu

Last reviewed: 
27 Sep 2022
Next review due: 
27 Sep 2025

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