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Discussion of the cancer-fighting properties of a chemical (variously referred to as amygdalin, laetrile, or vitamin B17) has been a fixture of the so-called alternative medicine movement for decades. Despite an exhaustive body of research demonstrating that its use is both ineffective and potentially dangerous, these claims still make their way onto the internet’s most popular natural health blogs and continue to fuel anti-government conspiracies. The story of B17 deficiency has the two key qualities of a classic snake oil campaign: a simple, easy cure for all cancer provided by Mother Nature herself, and a purported widespread conspiracy to prevent the public from knowing about it. This string of loosely connected words from a viral September 2016 post is representative of the way this issue is frequently framed: Before digging into this reassuring bit of nonsense, we have to be clear on one key point: The notion of vitamin B17 was essentially made up by a man named Ernst Krebs, Jr., inventor of a partially synthetic chemical called laetrile that was at one point rebranded as a vitamin in an effort to get around FDA new drug regulations. No official pharmacopoeia lists it as a vitamin, and it does not possess any of the required characteristics of a vitamin. In a hearing about an 1976 injunction demanding that a company cease selling supplements with this compound, a federal court described the vitamin defense as a patently absurd and transparent attempt to avoid the drug labeling provisions of the Federal Food, Drug, and Cosmetic Act. Amygdalin is a naturally occurring compound that can be found in a variety of foods, most notably bitter almonds and the pits of apricots and other fruits. Claims that it is a potential cancer therapy can be credited to the father and son team of Ernst Krebs Sr. (a doctor and pharmacist with a long history of promoting fringe folk remedies) and Ernst Krebs Jr. (who was not a doctor nor even the recipient of any degree in science, save an honorary doctorate from a now-defunct university). Their work is described in a 1981 review on the topic: One of the tell-tale warning signs of a pseudoscientific remedy is that the explanation for how it works (or even what it does, and in this case even what it is) changes every time someone points out that a previous explanation was demonstrably unworkable, without acknowledgement of the previous lack of veracity. There have been at least four explanations for why laetrile might work. As summarized by a National Institutes of Health Physician Data Query report, most invoke the fact that laetrile is toxic to cancer cells (which is almost certainly related to the fact that it metabolizes into cyanide) but not other cells: In fact, the rationale for laetrile’s efficacy is not the only thing that has shifted over the course of its promotion; what conditions or health problems it is meant to ameliorate have also jumped around, as discussed in a 1977 FDA report: The definition of what chemically constitutes both laetrile and vitamin B17 has been equally fluid. Though classically defined by Krebs Jr. as a specific compound named laevo-mandelonitrile-beta-glucuronoside, numerous tests have shown that this product is not what is found in most laetrile or B17 products. In many studies, amygdalin and laevo-mandelonitrile-beta-glucuronoside are taken to be the same thing, despite the fact that they are not (recall that the reason a synthetic version of amygdalin was needed was rooted in Kreb Sr.’s conclusion that the natural version was too toxic for human use). Other claims suggest an even broader definition, which includes an entire class of structurally related compounds variously named nitrilosides or laetrile. Overshadowing this unceasing onslaught quacktastic red flags are two hard truths: 1) there is effectively no evidence that laetrile, amygdalin, B17, etc., have any efficacy as a cancer treatment for humans and 2) there is plenty of evidence to suggest that amygdalin and related compounds are extremely toxic to humans, a problem compounded by the fact that several studies have shown that amygdalin supplements vary wildly in the accuracy of their concentrations and are completely unregulated. In response to pressure from pro-laetrile groups during its heyday in the 1970s, the National Cancer Institute conducted a retrospective review, published in 1976 of people who had been treated with laetrile for cancer. They did this by soliciting information by mail from 385,000 physicians and 70,000 other health professionals known to treat patients with laetrile, as well as by soliciting information directly from members of pro-Laetrile groups. Of the 70,000 cases estimated to have been treated with the chemical at the time, only 93 were submitted for review. A further 26 were eliminated due to insufficient data, revealing, ultimately, only six that could be described as producing a response: In a followup to this report, a 1982 human trial that treated 78 cancer patients with amygdalin, published the New England Journal of Medicine, concluded: A 2015 review of over 200 citations related to amygdalin, laetrile, and cancer concluded: These results are not to say that amygdalin and related compounds do not do anything. In that same 1982 human trial, researchers documented both the aforementioned lack of efficacy, as well its potentially fatal toxicity: This, too, was echoed in the previously cited 2015 evidence review, which stated: The weight of this evidence has not deterred natural health evangelists like Joseph Mercola (who was recently ordered by the FTC to pay back over five million dollars in money generated from selling his own brand of indoor tanning beds that, in his words, slash your risk of cancer) from suggesting that the weight of scientific evidence is on their side. Mercola, in a 2014 post that appears on many other websites, lists five studies which he says demonstrates the effectiveness of laetrile. None of these studies were based on human trials or data generated by the compound’s actual clinical use (unlike the large scale clinical trials and retrospective reviews and meta-reviews mentioned above); they were either cell line studies or studies based on laboratory animals. That promotion of vitamin B17 is still a viable business model online is thanks, in large part, to the efforts of individuals with political or financial motives, but whose medical background might best be described as non-existent. That movement got a huge lift in 1973 when a public relations officer at Sloan Kettering Hospital, which was given the task by the NIH of performing a series of laetrile trials, alleged a cover up of, and leaked, data that claimed potential for laetrile as an anti-cancer agent. Despite the fact that no scientist could reproduce those results in a series of followups, the view of a government cover-up created a media sensation, and has left a mark on its research that still resonates today. That former public relations writer, Dr. Ralph W. Moss (who has a Ph.D in classics, not science) is now one of the leading advocates for laetrile. For the low price of $297.00, he will provide you with a personalized Moss Report about your cancer diagnosis. He even provides one hour phone consultations to discuss treatment options. The legally required disclaimer on his website reads nothing Ralph W. Moss, PhD, says in your telephone consultation constitutes medical advice. Perhaps the most prominent force keeping the laetrile myth alive is the book World Without Cancer: The Story of Vitamin B17 (which was very positively reviewed by Dr. Ernst Krebs Jr himself!) by G. Edward Griffith, a libertarian activist with no medical training. Despite his book being basis for many pro-laetrile arguments, Griffith himself seems to be less enthused by that notion these days, as evidenced by this fairly convoluted introduction on his web site VitaminB17.org: The scientific view, however, has not shifted much at all. This 1981 assessment is still the opinion held by the scientific community today:
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