What is Laetrile?

Laetrile is also known as: Apricot pits, Vitamin B17, mandelonitrile-beta-glucuronide (semi-synthetic), mendelonitrile beta-D-gentiobioside (natural product), laevorotatory and mandelonitrile, purasin, Amygdalina, and nitriloside.

Application and Dosage

Laetrile

Laetrile is propagated as an alternative therapy for cancer. It is administered usually as part of metabolic therapy and is taken either orally as a pill, or by injecting into a vein or muscle. Treatment is usually started intravenously for a period of time (approximately two to three weeks) and then provided orally (maximum of 5 kernels at one time, or 1 gram of Laetrile) as a maintenance therapy. Laetrile can also be used in enema form, or can be applied directly to skin lesions. It is estimated that oral doses of approximately 50 to 60 apricot kernels, or 50 mg of Laetrile can be fatal (ref 1).

Ingredients

Laetrile in the US is not the same thing as Laetrile/Amygdalin used in Mexico. This is because the "Laetrile" used in Mexico may actually be simply crushed apricot kernels, rather than the semi-synthetic form of Laetrile (mandelonitrile-beta-glucuronide) used in the US. Therefore, not all studies of laetrile may have tested the same substance, making conclusions difficult. Incorrect labels have been found and samples tested have been contaminated with bacteria, toxins and other substances (ref 2). Treatment may cost thousands of Euros a week.

The following foods may also contain Laetrile in low and safe amounts as part of a balanced diet: the stones of fruits similar to apricots (eg apples, lemons, limes, cherries, prunes, plums, pears) millet, barley, buckwheat, maize, bamboo shots, clover sorghum, mung beans, lima and butter beans (and other pulses), flax seed, linseed, pecans, cashews, walnuts, raw almonds, celery, bean sprouts, carrots, alfalfa sprouts, watercress and sweet potato).

History

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"Laetrile has had a very long and detailed history. This includes inaccurate theories of how it works, conspiracy theories of unpublished research supporting its use, banning of its use in the US by the FDA, and the jailing of many supporters and suppliers"

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Amygdalin was first identified and isolated by French chemists in 1830 and was used as an anti-cancer agent in 1845 in Russia. By the 1920s Amygdalin had reached the US, but the early pill form was considered to be too toxic and its use was discontinued. In the 1950s an apparently non-toxic, semi-synthetic intravenous form of Amygdalin was developed by Dr. Krebs in the US, and this became known as Laetrile. In the 1970s Laetrile gained popularity either as a single-agent treatment or as part of a metabolic therapy programme (that also included high-dose vitamin supplements and enzymes). The popularity of Laetrile reached its peak in 1978 when it was reported that 70,000 people had been treated with it (ref.3).

Laetrile has had a very long and detailed history. This includes inaccurate theories of how it works, conspiracy theories of unpublished research supporting its use, banning of its use in the US by the Food and Drug Administration (FDA), and the jailing of many supporters and suppliers (including Dr. Krebs himself). The controversy continues with vendors’ internet sites being shut down and injunctions being served. In the UK, according to the Medicines and Healthcare products Regulatory Agency (MHRA), the status of Amygdalin/Laetrile/B17 is that it is a prescription only medicine. It is not a banned substance but it is unlicensed, and as such its availability is restricted through a prescription from a doctor. This means that a doctor can supply it to a patient should he or she consider it an appropriate treatment, however, the doctor does this under their own responsibility. No licensed products contain the Laetrile/Amygdalin/B17 substance.

Theories for mechanism of action

Four different theories have been put forward which aim to explain the anti-cancer activity of Laetrile. These are as follows:

  1. Trophoblastic theory was first put forwards by Beard (ref 4) in 1911. The theory suggests that all cancers arise from special cells which are randomly dispersed in the body during embryonic development (which would normally have become egg or sperm cells). Building on the trophoblast theory, Krebs suggested that the transformation of the rogue egg/sperm cells into a cancerous state could be prevented by ingesting Laetrile (ref 5). Trophoblast cancer cells are thought to have a different balance of enzymes in comparison to normal non-cancerous cells, that is, more beta-glucuronidase and less rhodanese than normal cells. Beta-glucuronidase breaks Laetrile down and produces cyanide (which kills the cell by shutting down aerobic respiration), however, rhodanese can convert cyanide into a relatively harmless compound (thiocyanate). As cancerous cells have less of the beta-glucuronidase enzyme to convert cyanide to a harmless form they are more effected by cyanide than healthy cells. Therefore, it is believed cancerous cells are more likely to be adversely effected by Laetrile, while normal cells are thought to be unaffected. However, there is no experimental evidence to support the idea that normal and malignant cells differ in their concentrations of these two enzymes (ref 6).
  2. Enzyme balance. The second theory of action of Laetrile is similar to the first in suggesting that cancerous cells have a different balance of enzymes. The main difference with this theory is that the trophoblastic explanation for cancer cell development is not used. Rather than beta-glucuronidase as in the previous theory, this second approach states that cancer cells have more beta-glucosidase and less rhodanese enzymes than normal cells, and therefore Laetrile negatively affects only cancerous cells as they are not protected by enough rhodanese. However, no experimental evidence exists to support this theory (ref 6).
  3. "Vitmamin B17" deficiency. The third theory is that cancer is a result of a metabolic disorder caused by a deficiency in so-called "vitamin B17". Dr. Krebs used Vitamin B17 as another name for Laetrile, and it is thought that by restoring this missing "vitamin" in the body, health can be restored. Studies have shown that the vitamin status of an individual can determine the development of cancer (ref 7). However, there is no evidence that B17 or Laetrile is needed for normal metabolism or that it even functions as a vitamin in humans or animals (ref 8).
  4. Theory four suggests that as well as disrupting aerobic respiration, the cyanide released by Laetrile increases the acid content of tumours and leads to the destruction of lysosomes within the tumour cells. The lysosomes release their contents (i.e. enzymes which can break down other cellular molecules) thereby killing the cancer cell(s) and stopping the growth of the tumour. However, this theory is not supported by evidence (ref 9).

References

1. Davignon, JP, Trissel, LA, & Kleinman, LM. Pharmaceutical assessment of amygdalin (Laetrile) products. Cancer Treatment Reports. 1978; 62 (1): 99-104.
2. Chandler, RF, Phillipson, JD & Anderson, LA. Controversial Laetrile. Journal of Pharmacology. 1984; 232: 330-332.
3. Ellison, NM, Byar, DP, & Newell, GR. Special report on Laetrile: the NCI Laetrile Review. Results of the National Cancer Institute's retrospective Laetrile analysis.
New England Journal of Medicine. 1978; 7;299 (10):549-52.
4. Beard J. The Enzyme Treatment of Cancer, 1911. London: Chatto and Windus.
5. Krebs, ET Jr., Krebs, ET Sr., & Beard, HH. The Unitarian or trophoblastic thesis of cancer. Medical Record. 1950; 153 (7): 149-74.
6. Conchie, J, Findlay, J, and Levvy, GA. Mammalian glucosidases: distribution in the body. Biochemical Journal. 1959; 71: 318-25.
7. IARC Handbooks on Cancer Prevention. 2003. Vol. 8 ‘Fruit and Vegetables’ WHO.
8. Vickers A. Alternative cancer cures; "unproven" or “disproven". CA: A Cancer Journal for Clinicians. 2004; 54, 110-8.
9. Greenberg, DM. The case against Laetrile: The fraudulent cancer remedy. Cancer. 1980; 15; 45 (4) :799-807.