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Laetrile (amygdalin or vitamin B17)

Laetrile is promoted as an alternative cancer treatment but there is no evidence that it works.

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 and the pips of many fruits, particularly apricot pips or kernels. It is also found in plants like lima beans, clover and sorghum.

Some people call laetrile vitamin B17, although it isn’t a vitamin. Its other names are:

  • mandelonitrile beta D gentiobioside
  • mandelonitrile beta glucuronide
  • laevorotatory
  • purasin
  • amygdalina
  • nitriloside

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. But there is no scientific evidence that laetrile or amygdalin can treat cancer or any other illness. Despite this, it is still promoted as an alternative cancer treatment.

Alternative treatment means that people use it instead of conventional cancer treatments such as cancer drugs or radiotherapy. We do not recommend that you 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 also do not recommend that you use laetrile alongside your cancer treatment.

Why people with cancer use laetrile

There is no evidence that laetrile can help with cancer, but some people use it because they believe it might:

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

What taking laetrile involves

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 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. 

They usually also suggest that you take high doses of vitamins and follow a special diet. So it can be quite a rigid and complex treatment to stick to.

Side effects

Laetrile contains cyanide, which is a type of poison. 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

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
  • 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 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.

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.

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.

In two laboratory studies, amygdalin has shown anti cancer activity 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. 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. This research was first reported in 1978 and 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 people on its website. They sponsored two published studies in the late 1970s and early 1980s.

The first study involved only 6 people and was to test what levels of laetrile were safe. The researchers reported very few side effects but 2 people 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 in 175 people. Only 1 person had any apparent response to laetrile and this only lasted for 10 weeks. Seven months after the study, all the 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 2015. It 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 is allowed to sell laetrile in the European Union because there is no evidence that it works, and because of its serious side effects. It is also banned in the USA by the Food and Drugs Agency (FDA).

A US website estimated that laetrile injections for 21 days to start the treatment costs 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 airfare and accommodation.

Be careful when reading any websites that promote the use of laetrile or recommend treatment in overseas clinics.

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 or not to use an alternative cancer therapy such as laetrile.

But stopping cancer treatment such as chemotherapy or radiotherapy for an unproven treatment could be very harmful to your health. We do not recommend that you replace your conventional cancer treatment with any type of alternative cancer therapy.

Many websites promote laetrile as a cure for 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.

Last reviewed: 
30 Jan 2015
  • Complete Guide to Complementary and Alternative Cancer Therapies
    American Cancer Society, 2009

  • A clinical trial of amygdalin (laetrile) in the treatment of human cancer
    CG Moertel and others
    New England Journal of Medicine, 1982. Volume 306, Issue 2

  • A pharmacologic and toxicological study of amygdalin
    CG Moertel and others
    JAMA, 1981. Volume 245, Issue 6

  • Controversial laetrile
    RF Chandler and others
    Journal of Pharmacology, 1984. Volume 232

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