Laetrile

Scientific/ common names

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.

Ingredients

Laetrile is an acronym used to describe a purified, semi-synthetic form of Amygdalin (LAEvorotatory and mandeloniTRILE). Amygdalin is a naturally occurring plant compound that contains sugar and produces cyanide and is found primarily in the kernels of apricots, peaches and bitter almonds and also in plants such as lima beans, clover and sorghum.

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 substances1. Several foods may also contain Laetrile in low and safe amounts as part of a balanced diet.

Application and dosage

Laetrile is usually administered 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.

History

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)2.

Claims of efficacy/mechanism(s) of action/alleged indication

Powerful claims of anti-cancer effects have been made by distributors and hospitals in Mexico where Laetrile is used. Proponents suggest that cyanide is responsible for the anti-cancer action, which is released from the enzymatic degradation of laetrile3. However, none of these claims have been supported by research evidence. Supporters of Laetrile often use anthropological evidence to back up their anti-cancer claims. Such evidence comes from studies of remote cultures who consume high levels of foods rich in nitrisolides (Amygdalin), for instance, the Hunza, aboriginal Eskimo, the Hopi and Navajo Indians4. However, it is important to remember that, even though studies of these populations have reported low incidences of cancer, this must be viewed in context and other unmeasured variables taken into account.

Cyanide released from enzymatic degradation of laetrile or amygdalin is believed to be the ingredient responsible for the alleged anti-cancer action. Proponents claim that malignant cells are specifically vulnerable to cyanogenic glycosides because of two characteristics: a higher level of beta-glucosidases and beta-glucuronidase compared to normal cells, which would lead to a more rapid intracellular release of cyanide from laetrile or amygdalin and a deficiency in rhodanese, an enzyme that converts cyanide into the harmless compound thiocyanate. Another theory claims that cancer develops due to the deficiency of a vitamin, named "vitamin B17", which was the name that the chemist E.T. Krebs gave to laetrile5.

Prevalence of use

The popularity of Laetrile reached its peak in 1978 when it was reported that 70,000 people had been treated with it2. Current prevalence data are not available.

Legal issues

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 considers it an appropriate treatment, however, the doctor does this under their own responsibility. No licensed products contain the Laetrile/Amygdalin/B17 substance.

Cost and expenditures

Laetrile tablets are available via the internet for approximately 100 USD for 100 tablets. Since there are no clear guidelines on dosage and length of treatment, it is not possible to give an overall cost for laetrile treatment.