laetrile

(lā'ĭ-trĭl', -trəl)

[lae(vorotatory) (variant of LEVOROTATORY) + (NI)TRILE.]

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Name given to an extract of apricot kernels, amygdalin. Claimed as a cancer cure, although there is no supporting evidence, and sometimes called vitamin B₁₇, although there is no evidence that it is a dietary essential or has any metabolic function.

A water-soluble compound first extracted from apricot kernels in the 1950s. Its full scientific name is laevo-mandelonitrile-beta-glucuronoside but it is also known as amygdalin. It is often present in foods with vitamin B complex. This has led to laetrile being marketed by some producers as vitamin B₁₇, but it is not a vitamin and has no known function in the body.

Laetrile is a source of organic cyanide. Cancer cells are believed to convert this into inorganic cyanide that destroys the cells. Consequently, laetrile has been used in cancer therapy. However, its use is very controversial. Excess laetrile is toxic to normal cells and causes cold sweats, headaches, nausea, lethargy, breathlessness, and low blood pressure. Consequently, the sale of laetrile has been restricted in some countries due to its potential toxicity. In the UK it is available only on prescription. Its use in the USA is illegal because of its toxicity, and because there is not enough convincing evidence that it is beneficial.

A water-soluble compound often found with members of the vitamin B complex. It is sometimes marketed as a vitamin, but it is not a true vitamin.