Laetrile



Laetrile, or laevomandelonitrile, is a trade name used for a synthetic form of amygdalin, a cyanogen compound found in the seeds of stone fruits of the Prunus genus (particularly apricots) that has been sold as a cancer cure for many years by quacks. In the last few years, it's often misrepresented as vitamin B17 (even though it's not a vitamin).

Laetrile can refer to two different substances: amygdalin, which occurs naturally in apricot and peach pits and in minuscule amounts in some foods (bitter almonds, brewer's yeast, buckwheat, sorghum, apple seeds, etc.), and synthetic Laetrile, a distinct but chemically related substance. The "laetrile" obtained in Mexico is usually in fact amygdalin. Laetrile treatment is generally associated with the expat altie community in Mexico, and is not approved for use in the United States due to a lack of evidence that it produces any effect other than cyanide poisoning in the patient. In the State of Indiana, a physician may prescribe "amygdalin (laetrile)" for use as a "dietary supplement".

Proposed mechanism and the sad truth
The cancer-killing effect of amygdalin is attributed to the hydrogen cyanide ions, or cyanides, formed as a result of its decomposition. In addition to this, amigdalin decomposes into compounds that are not important, including benzoaldehyde and glucose. Cyanide ions block the action of cytochrome oxidase in the respiratory chain, or simply cause cell death by asphyxiation. So, in order for the ions to work, the cell must use cytochromes for its respiration and hence must use the respiratory chain. In most healthy cells, this is the case, as cellular respiration consists of three steps: glycolysis, the Krebs cycle and the respiratory chain. However, cancer cells are far more dependent on glycolysis than the latter two. This means that the effect of cyanide on most cancer cells is very limited.

Proponents of the use of leatril to treat cancer believe that cancer cells contain an enzyme that breaks down amigdalin to cyanide ions, which are thought to damage the cell, while healthy cells contain another enzyme  that converts cyanide ions to rhodanides (thiocyanates) excreted in the urine with much less toxicity. However, cancer cells have been found to contain rhodanese in amounts comparable to that of liver and kidney. Some cancer cells have also been found to contain only trace amounts of β-D-glucosidase.

Laetrile fans often cite anecdotal evidence of individual cases where laetrile appeared to work, but in every case where a sufficiently large sample size was studied, laetrile has not been shown to be effective (i.e., no statistically significant results). In spite of all this, laetrile is still presented as a "suppressed" treatment by many conspiratorially-minded quacks.

Then there is the fact that eating tons of fruit seeds is a common suicide practice because it allows for a quick death due to overdose of cyanide. Numerous cases of cyanide poisoning after taking amygdalin have been reported. There really is nothing holding you back from dying via those seeds: fruit is not a.

Literature

 * Braico KT. Humbert JR. Terplan KL, et al.: Laetrile intoxication: report of a fatal case. New Engl. J. Med. 238 240,1979
 * Milazzo, S. et al. (2006): Laetrile for cancer: a systematic review of the clinical evidence. Supportive Care in Cancer. 15(6), p. 583–595.
 * Herbert, V. (1979): Laetrile: the cult of cyanide. Promoting poison for profit. Am. J. Clin. Nutr. Bd. 32, S. 1121-58. PMID 219680 PDF
 * 'Unproven Methods of Cancer Management. Laetrile. In: 1991, CA Cancer J. Clin. Bd. 41, p. 187-192. PMID 1902140 PDF
 * Moertel, C.G., et al. (1982): A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N. Engl. J. Med. Bd. 306, p. 201-206. PMID 7033783
 * Brant J, Graceffa J: Rutherford, Priviteria, and Chad Green: Laetrile's setbacks in the courts. Am. J. Law Med. 1980 Summer;6(2):151-71
 * Irving J. Lerner: Laetrile: A Lesson in Cancer Quackery. CA Cancer J. Clin. 1981; 31:91-95. doi: 10.3322