Er is veel verwarring over de namen Laetrile, amygdaline en vitamine B17. Amygdaline is een natuurlijke stof die onder andere uit bittere amandelen wordt bereid, maar laetrile is chemisch. Laetrile wordt gefabriceerd door scheikundige behandelingen van amygdaline. Laetrile en vitamine B17 zijn hetzelfde en dat betekent dat B17 geen vitamine is. In praktijk worden alle drie namen door elkaar gebruikt. Dat veroorzaakt veel verwarring.
Geschiedenis
Amygdaline werd in 1830 uit bittere amandelen geïsoleerd door de chemici Robiquet en Boutron Charlard. Daarna probeerden Duitse wetenschappers amygdaline in 1892 uit als medicijn voor kanker. Het resultaat: geen verbetering van de kanker, wel cyanidevergiftiging. Te gevaarlijk! Dat leek het einde van het verhaal te zijn.
Maar dat was het niet. De naam laetrile dook meer dan een halve eeuw later voor het eerst op. In 1950 bedacht Ernst Krebs Jr. de naam voor het door hem en zijn vader ontwikkelde “veredelde” analogon (verschillende chemische verbindingen met identieke werking) van amygdaline. Laetrile was gewoon amygdaline dat een scheikundige bewerking had ondergaan.
Laetrile is daarom geen natuurproduct. Vader en zoon Krebs wisten er een octrooi op te krijgen. Er werd beweerd dat laetrile wel een veilig middel tegen kanker zou zijn, maar bewijzen daarvoor hadden ze niet. Ze zijn er overigens nog steeds niet. Er zijn intussen wel verscheidene analoga van laetrile gemaakt. In 1958 werd een poging gedaan om laetrile onder de naam “vitamine B17” erkend te krijgen. Laetrile heeft echter niet de eigenschappen die voor vitamines vereist zijn, al was het maar omdat het geen natuurlijke stof is. Bovendien is het niet onmisbaar voor het lichaam. Vitamine B17 is als het ware een synoniem voor laetrile. Niettemin noemt Ernst Krebs Jr. jaren later B17 een natuurlijke vitamine.
Wetenschappelijk onderzoek naar de werkzaamheid en de veiligheid van laetrile is door vader en zoon Krebs en andere verdedigers van het gebruik van laetrile overigens niet gedaan. Maar ze klaagden wel over het gebrek van belangstelling van de kant van de reguliere geneeskunde! Dat de Amerikaanse autoriteiten in de vorm van rechtspersoon FDA (Food and Drug Administration) weigerden laetrile als een geneesmiddel te registreren was niet, zoals laetrile-aanhangers beweren, omdat het een natuurlijk middel is. Dat is het in de verste verte niet. De FDA weigerde registratie omdat er geen bewijs van werkzaamheid en veiligheid was.
Vanaf 1972 hebben enkele topziekenhuizen in de VS een gedegen onderzoek uit naar de werking van zowel laetrile als amygdaline uitgevoerd. In een onderzoek met 178 patiënten met kanker werd laetrile vergeleken met een placebo. Het resultaat was hetzelfde als bijna 100 jaar eerder: geen verbetering van de kanker; er waren wel gevallen van cyanidevergiftiging.
In 2011 zijn alle bekende studies met laetrile en amygdaline verzameld door de internationale Cochrane-society. De conclusie luidde dat er geen bewijs van de werkzaamheid is van laetrile of amygdaline tegen kanker is, maar wel bewijs dat deze stoffen gevaarlijk zijn. Laetrile noch amygdaline mogen worden aanbevolen tegen kanker, concluderen de Cochrane-onderzoekers.
Het voornaamste bijverschijnsel van laetrile, vitamine B17 en ook van amygdaline, is cyanidevergiftiging. De vergiftiging openbaart zich als misselijkheid, hoofdpijn, duizeligheid, beschadiging van de lever, gebrek aan zuurstof, verlaging van de bloeddruk, koorts, verlies van het evenwicht en moeite met wandelen, verwarring, coma en uiteindelijk overlijden. Vergiftiging is voornamelijk het gevolg van het slikken van laetrile zowel als van amygdaline, zoals in 1892 voor amygdaline al is aangetoond. Bij injecties komt vergiftiging nauwelijks voor.
Het eten van pitten van vruchten die rijk zijn aan amygdaline moet ook worden afgeraden. Het betreft pitten van met name abrikozen en perziken. Let wel, pitten, niet het gewone vruchtvlees. Voor abrikozenpitten bestaat inmiddels een waarschuwing van de VWA (nu de NVWA). Ze kunnen ruim 800 tot 3000 milligram blauwzuur (cyanide) per kilogram vrij maken. Dertig gram abrikozenpitkernen kunnen al dodelijk zijn. Voor kinderen geldt naar gelang het lichaamsgewicht een kleinere hoeveelheid. Het Bureau Risicobeoordeling van de VWA noemde dit in januari 2007 een hoog risico. Maatregelen om het risico te beperken zijn er echter nog steeds niet genomen.
Support Care Cancer. 2007 Jun;15(6):583-95. Epub 2006 Nov 15.Laetrile for cancer: a systematic review of the clinical evidence. Milazzo S1, Lejeune S, Ernst E.
Many cancer patients treated with conventional therapies also try 'alternative' cancer treatments. Laetrile is one such 'alternative' that is claimed to be effective by many alternative therapists. Laetrile is also sometimes referred to as amygdalin, although the two are not the same.
OBJECTIVE:
The aim of this review is to summarize all types of clinical data related to the effectiveness or safety of laetrile interventions as a treatment of any type of cancer.
MATERIALS AND METHODS:
All types of clinical studies containing original clinical data of laetrile interventions were included. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1951), EMBASE (from 1980), Allied and Complementary Medicine (AMED), Scirus, CancerLit, Cumulative Index to Nursing and Allied Health (CINAHL; all from 1982), CAMbase (from 1998), the MetaRegister, the National Research Register, and our own files. For reports on the safety of laetrile, we also searched the Uppsala database. No language restrictions were imposed.
RESULTS:
Thirty six reports met our inclusion criteria. No controlled clinical trials were found. Three articles were nonconsecutive case series, 2 were consecutive case series, 6 were best case series, and 25 were case reports. None of these publications proved the effectiveness of laetrile.
CONCLUSION:
Therefore, the claim that laetrile has beneficial effects for cancer patients is not supported by sound clinical data.
Other common name(s): amygdalin, vitamin B17, Amigdalina B-17
Scientific/medical name(s): mandelonitrile beta-D-gentiobioside (the form found most often in Mexican clinics), mandelonitrile-beta-glucuronide (this is the patented drug Laetrile)
Laetrile is a chemically modified form of amygdalin, a naturally-occurring substance found mainly in the kernels of apricots, peaches, and almonds. However, the terms amygdalin and Laetrile are often used interchangeably. The name Laetrile is also used to describe a closely related and partly man-made substance. Laetrile and amygdalin are promoted as alternative cancer treatments.
Overview
Available scientific evidence does not support claims that Laetrile or amygdalin is effective in treating cancer or any other disease. Both contain a small amount of a substance that can be converted to cyanide in the body, and several cases of cyanide poisoning have been linked to the use of Laetrile. The U.S. Food and Drug Administration (FDA) has not approved Laetrile as a medical treatment in the United States.
How is it promoted for use?
Supporters once called Laetrile "the perfect chemotherapeutic agent," as it was said to kill cancer cells while being non-toxic to normal cells. Promoters claim that societies with diets rich in amygdalin, such as the Hunza and the Karakorum (of the region bordering Pakistan, India, and China), are "cancer-free peoples." Supporters also say that Laetrile can prevent cancer and can help patients stay in remission. It is also promoted to provide pain relief to people with cancer. Other reported uses for Laetrile have been in the prevention and treatment of high blood pressure and arthritis.
There are several explanations for how Laetrile is proposed to work. Supporters claim that cancer cells contain more of a certain enzyme that splits the Laetrile molecule and releases the cyanide within it. The cancer cell then is supposed to die from cyanide poisoning. Normal cells supposedly do not have as much of this enzyme and instead contain an enzyme that renders the Laetrile harmless. Supporters claim that normal cells are not affected for this reason.
Another popular theory is that cancer is really a "vitamin deficiency" and that Laetrile is the missing "vitamin B17." Laetrile does not meet the widely accepted scientific definition of a vitamin, in that it has not been proven to be essential to achieving or maintaining good health.
What does it involve?
Amygdalin is most commonly extracted from apricot pits. Laetrile is a related substance, which has a slightly different chemical structure. Laetrile (or amygdalin) is often taken as part of a metabolic therapy that includes a specific diet with high doses of vitamins (see Metabolic Therapy). Although no standard treatment plan exists, a typical treatment consists of injecting Laetrile or amygdalin into a vein each day for 2 to 3 weeks, followed by taking tablets by mouth as a maintenance therapy.
Laetrile and amygdalin are also used in enemas and in solutions applied directly to diseased areas on the skin. Chemical analyses of products sold as Laetrile showed that the actual ingredient is often amygdalin rather than Laetrile. For this reason, and because the terms are often used as synonyms, both substances are called Laetrile in the remainder of this document unless otherwise noted.
Laetrile treatments may cost thousands of dollars per week. Laetrile is commonly used in some hospitals and clinics in northern Mexico because it is difficult to get in the United States.
What is the history behind it?
"Bitter almonds" have been used as a medical remedy for thousands of years by cultures as diverse as the ancient Egyptians, Chinese, and Pueblo Indians. In 1802, a chemist discovered that distilling the water from bitter almonds released hydrocyanic acid. In the 1830s, the source of this hydrocyanic acid was purified and called amygdalin. It was thought to be the active ingredient in bitter almonds.
According to a 1991 review, the current use of Laetrile can be directly attributed to the theories of Ernst T. Krebs, Sr., MD, which were first proposed in the 1920s. Krebs tested an extract from apricot pits to treat cancer, but the pills proved too toxic for human use.
Around 1952, his son, Ernst T. Krebs, Jr., changed the process of extracting amygdalin and created a chemically modified version, which he named Laetrile. He claimed that the new substance was more potent as an anti-cancer drug than naturally-occurring amygdalin. Despite this chemical distinction, both proponents and skeptics commonly refer to both substances as Laetrile. Adding to this confusion is the fact that many products sold as Laetrile consist mostly of amygdalin. It is also the form most often used by Mexican cancer clinics.
The same 1991 review notes that, beginning in 1957, Laetrile was repeatedly tested against tumor cells implanted in animals. At least a dozen separate sets of experiments were done at seven institutions. Targets included several different types of cancer. The conclusion was that Laetrile did not have any anti-tumor activity.
The FDA placed sanctions against the sale of Laetrile. In 1977, the FDA commissioner stated that there was no evidence for the safety or effectiveness of Laetrile. Because of the risk of cyanide poisoning, the government has banned the transport of Laetrile into the United States or across state lines, as well as the use of Laetrile in states without laws specifically allowing it. Since 2000, there have been several instances of prosecution because of Laetrile transport across state lines. Nonetheless, products advertised as Laetrile and amygdalin can still be purchased via many websites.
What is the evidence?
From the 1950s through the 1970s, Laetrile grew in popularity in the United States as an alternative treatment for cancer. For this reason, and despite the lack of scientific evidence that Laetrile was effective, the National Cancer Institute (NCI) studied it in 1978 through a retrospective case review (a study that looks back at cases from the past). The NCI sent letters to more than 400,000 doctors and other practitioners, asking them to submit positive results from cases involving Laetrile. While an estimated 75,000 people in the United States had taken Laetrile, only 93 "positive" cases were submitted, and in only 6 of those was there evidence of significant tumor shrinkage.
Despite this record of minimal response, a clinical trial in humans was conducted in 1981. It did not show any anti-cancer effect of Laetrile. This study of Laetrile on humans was performed between 1979 and 1981 at medical centers around the country. About 175 patients with different types of cancer were treated with a commonly used regimen of Laetrile plus metabolic therapy (see Metabolic Therapy). Published in 1982, it reported that one patient had major tumor shrinkage (a partial response) at first. Of the patients, 91% of their cancers had progressed (worsened) after 3 months, and median survival was less than 5 months. In all patients, their cancer grew within 8 months of starting treatment.
A 1991 NCI review of the evidence of Laetrile’s effectiveness stated that “scientific studies were conducted for more than 20 years, starting in the mid-1950s, looking for evidence of antitumor efficacy by Laetrile. In no instance was evidence found that treatment with Laetrile results in any benefit against tumors in animals.”
In contrast to the NCI findings, one of the leading proponents of Laetrile claims to have treated nearly 30,000 cancer patients in several studies of the drug with promising results. However, these results have not been reviewed or repeated by the scientific medical community. Available published information from credible sources does not support the reports of good results and cures from Laetrile treatment.
As for the healthy Hunza and Karakorum people, there are many factors in these isolated mountain communities that differ markedly from Western habits, which could affect their cancer rates. For example, the Hunza people have long eaten home-grown fruits, nuts, vegetables, and whole grains and gotten plenty of exercise. Their traditional diet includes modest amounts of meat, but not refined or processed foods. Traditionally, they don’t smoke, overeat, or drink too much alcohol. These habits are very much in line with the American Cancer Society guidelines for cancer prevention. Unfortunately, the healthy traditions of these cultures may be changing as the outside world encroaches.
The consensus of available scientific evidence does not support claims that laetrile is an effective anti-cancer treatment, either in animal studies or in human clinical trials. Cancer cells do not seem to be more susceptible to the effects of laetrile than normal cells. The successes claimed by its supporters are based on individual reports, testimonials, and publicity issued by promoters.
Are there any possible problems or complications?
This substance has not been thoroughly tested to find out how it interacts with medicines, foods, herbs, or dietary supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.
The use of Laetrile has been linked to cyanide toxicity and death in a few cases, especially when it was being taken by mouth. Although drug interactions are unknown, at least one case report suggests that vitamin C can increase the amount of cyanide released from Laetrile in the body. This can further raise the risk of cyanide poisoning. This risk is also likely to be increased if the person also eats raw almonds or crushed fruit pits while taking Laetrile. Eating fruits and vegetables that contain beta-glucosidase (such as celery, peaches, bean sprouts, and carrots) may increase the risk of cyanide poisoning. The symptoms of cyanide poisoning include weakness, confusion, and shortness of breath, sometimes with headache, dizziness, or sleepiness. The skin, mouth, and other mucous membranes may look very pink or red. Seizures and coma can result, and breathing may stop. Emergency help is needed for cyanide poisoning. Always tell your doctor, pharmacist, and other health professionals about any supplements or herbs you are taking.
This treatment should be avoided by children, and by women who are pregnant or breast-feeding. Relying on this type of treatment alone, and avoiding or delaying conventional medical care for cancer, may have serious health consequences.
References
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Memorial Sloan-Kettering Cancer Center. About herbs: Amygdalin. 2011. Accessed at www.mskcc.org/mskcc/html/69118.cfm on July 17, 2012.
Milazzo S, Ernst E, Lejeune S, et al. Laetrile treatment for cancer. Cochrane Database Syst Rev. 2011 Nov 9;11:CD005476.
Milazzo S, Lejeune S, Ernst E. Laetrile for cancer: a systematic review of the clinical evidence. Support Care Cancer. 2006.
Moertel CG, Fleming TR, Rubin J, et al. A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. N Engl J Med. 1982;306:201-206.
National Cancer Institute Physician Data Query (PDQ). Laetrile/Amygdalin. 2012. Accessed at www.cancer.gov/cancertopics/pdq/cam/laetrile/healthprofessional on July 17, 2012.
Wilson B. The rise and fall of laetrile. Rev 2012. Accessed at www.quackwatch.org/01QuackeryRelatedTopics/Cancer/laetrile.html on July 17, 2012.
Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.