Lack of context: In the body, amygdalin is broken down into cyanide, a potentially deadly poison that has caused multiple cases of cyanide poisoning among people using amygdalin for therapeutic purposes.
FULL CLAIM: Vitamin B17 “was banned by the US because of its cancer-killing properties”
Social media platforms have become a major source of unproven cancer cures and alternative treatments. Some of these alleged remedies might be toxic or reduce the effectiveness of proven medical treatments. But even those that aren’t harmful per se still pose a genuine threat to cancer patients, as they might lead some patients to delay or reject clinically proven treatments, which is associated with lower chances of surviving[2,3].
On 1 March 2023, a Facebook reel with more than 1.6 million views claimed that “Vitamin B17”, a compound present in apricot kernels, “was banned by the U.S. because of its cancer-killing properties”.
“Vitamin B17” is the name that some people use to refer to amygdalin, a compound present in some plants like clover and notably in the seeds of fruits from the Rosaceae family, such as bitter almonds, apricots, plums, and cherries.
But amygdalin isn’t a vitamin and the reel’s claim that the U.S. Food and Drug Administration (FDA) banned the sale of products containing amygdalin to cover up an effective cancer treatment is also false. Instead, the ban is because there’s no evidence that amygdalin offers health benefits and it has the potential to cause harm. Below, this review explains in detail the state of the scientific evidence on amygdalin’s alleged cancer-fighting properties.
Amygdalin isn’t a vitamin
The U.S. National Cancer Institute defines vitamins as “nutrients that the body needs in small amounts to function and stay healthy”. Known vitamins include A, C, D, E, and K, and the B vitamins B1, B2, B3, B5, B6, B7, B9, and B12 but not amygdalin.
Vitamins are proven essential for correct body function up to the point that a deficiency in any of them can lead to health problems. Contrary to claims that cancer arises from a “vitamin B17 deficiency”, there is no evidence suggesting that amygdalin carries any essential function in the body, or that the lack of amygdalin results in poorer health. In fact, consuming amygdalin can lead to potentially serious toxicity.
Amygdalin can cause cyanide poisoning
One well-known characteristic of amygdalin is its capacity to release hydrogen cyanide when it breaks down in the intestine. Hydrogen cyanide is known as a potentially deadly poison that interferes with cells’ ability to use oxygen. This mode of action of cyanide directly contradicts the mechanism proposed by the Facebook user, who claimed that B17 kills cancer cells because it “put[s] oxygen and hydrogenate[s] cells again”.
Most cells preferentially obtain their energy through aerobic respiration, a process that requires oxygen. By depriving the cells of oxygen, cyanide forces them to produce energy through a much less efficient process called anaerobic respiration or anaerobic glycolysis which involves burning glucose. This process produces lactic acid, which due to cyanide blockage of respiration, accumulates rapidly in the body up to levels causing metabolic acidosis. This condition impairs organ functions and can ultimately lead to death.
Even low doses of hydrogen cyanide can cause symptoms of cyanide poisoning, including chest pain, changes in the rate of heart beating and breathing, confusion, nausea, and weakness. Upon high levels of exposure, cyanide can be fatal or lead to serious problems such as loss of consciousness, seizures, and coma.
Regularly consuming extracts from apricot kernels, as the Facebook reel recommended, exposes the person to dangerous cyanide levels. According to the European Food Safety Authority, “Eating more than three small raw apricot kernels, or less than half of one large kernel, in a serving can exceed safe [cyanide] levels”. The safety threshold is even lower for toddlers, for whom consuming even one small apricot kernel can pose a health risk. Like the FDA, the European Union doesn’t permit the sale of amygdalin-containing products.
The use of amygdalin for treating cancer has been disproven
Based on its capacity for releasing cyanide, amygdalin was proposed as a cancer treatment in the mid-1800s. However, this use was quickly abandoned after initial studies revealed amygdalin as ineffective and toxic.
Around 1950, physician Ernst T. Krebs and his son Ernst Krebs, Jr. started producing and promoting a chemically modified form of amygdalin called laetrile (laevo-mandelonitrile-beta-glucuronoside). Krebs and his son claimed that laetrile selectively killed cancer cells because the enzyme beta-gluconoridase that broke down the compound into cyanide accumulated in tumors but not in healthy cells.
An increasing use of laetrile by general practitioners in California led the Cancer Commission of the California Medical Association to fund in 1953 a multicentric study to investigate the effects of this compound as a cancer treatment. The research concluded that amygdalin didn’t show any therapeutic effects in experimental animals and cancer patients.
In addition, the Commission found that “the total amount of beta-glucuronidase present in normal tissues in almost any cancer patient considerably exceeds that which is present in neoplastic tissue”. In other words, the enzyme was more abundant in healthy tissue than in abnormally grown (neoplastic) tissue, which meant that laetrile’s proposed mechanism of action of selectively killing only cancer cells and leaving healthy cells alone was implausible.
Despite the evidence showing that laetrile was ineffective against cancer, the compound continued to be heavily promoted as an alternative cancer therapy in Europe and the U.S. in the 1960s and 1970s. During that time, multiple researchers re-evaluated its effects, obtaining mostly negative results in experimental animals[5-8].
In 1978, the National Cancer Institute carried out a review of cancer cases that U.S. practitioners had reported to successfully treat with laetrile (the review can be read in full here). Among the 67 records submitted, the National Cancer Institute could find evidence of a response to the treatment in only six of them.
In 1982, the New England Journal of Medicine published the results of the first clinical trial on laetrile involving 178 cancer patients, although the trial lacked a control group. All the participants received laetrile combined with a “metabolic therapy” commonly used with laetrile at that time and involving dietary changes restricting the use of caffeine, sugar, meats, dairy products, eggs, and alcohol, enzyme, and vitamin supplements. The researchers evaluated whether the treatment improved the disease course and found no benefits of laetrile. However, some participants developed cyanide toxicity that the researchers defined as “approaching the lethal range”.
Later research kept showing no benefit of laetrile or amygdalin extracted from apricot seeds in cancer patients. In 2015, a Cochrane systematic review that evaluated all previous studies on these compounds concluded:
“The claims that laetrile or amygdalin have beneficial effects for cancer patients are not currently supported by sound clinical data. There is a considerable risk of serious adverse effects from cyanide poisoning after laetrile or amygdalin, especially after oral ingestion. The risk-benefit balance of laetrile or amygdalin as a treatment for cancer is therefore unambiguously negative” [emphasis added].
In short, apart from a few anecdotal reports, the evidence clearly indicates that laetrile and amygdalin are not only ineffective at treating cancer but they can also poison you.
The use of laetrile in cancer patients has been described in the scientific literature as “remunerative” quackery. But after many years of quiescence, the compound was resuscitated in the 2000s, rebranded as “vitamin B17”, likely as a way to get around FDA regulations.
Websites illegally selling “vitamin B17” and apricot kernels as an alternative cancer therapy continued to proliferate online, many appealing to the naturalness of this product as supposed evidence that it is good and safe. However, natural doesn’t necessarily mean safe, something that becomes evident in the case of a compound that can break down in your body into an actual poison such as cyanide.
- 1 – Johnson et al. (2022) Cancer Misinformation and Harmful Information on Facebook and Other Social Media: A Brief Report. Journal of the National Cancer Institute.
- 2 – Johnson et al. (2018) Complementary Medicine, Refusal of Conventional Cancer Therapy, and Survival Among Patients With Curable Cancers. JAMA Oncology.
- 3 – Johnson et al. (2018) Use of Alternative Medicine for Cancer and Its Impact on Survival. Journal of the National Cancer Institute.
- 4 – Haisman & Knight (1967) The enzymic hydrolysis of amygdalin. Biochemical Journal.
- 5 – Wodinsky & Swiniarski (1975) Antitumor activity of amygdalin MF (NSC-15780) as a single agent and with beta-glucosidase (NSC-128056) on a spectrum of transplantable rodent tumors. Cancer Chemotherapy Reports.
- 6 – Laster & Schabel (1975) Experimental studies of the antitumor activity of amygdalin MF (NSC-15780) alone and in combination with beta-glucosidase (NSC-128056). Cancer Chemotherapy Reports.
- 7 – Hill et al. (1976) Failure of amygdalin to arrest B16 melanoma and BW5147 AKR leukemia. Cancer Research.
- 8 – Chester et al. (1978) Antitumor tests of amygdalin in spontaneous animal tumor systems. Journal of Surgical Oncology.
- 9 – Ellison et al. (1978) Special Report on Laetrile: The NCI Laetrile Review — Results of the National Cancer Institute’s Retrospective Laetrile Analysis. New England Journal of Medicine.
- 10 – Moertel et al. (1982) A Clinical Trial of Amygdalin (Laetrile) in the Treatment of Human Cancer. New England Journal of Medicine.
- 11 – Hauser (1993) Unproven methods in cancer treatment. Current Opinion in Oncology.
- 12 – Milazzo et al. (2015) Laetrile treatment for cancer. Cochrane Database of Systematic Reviews.
- 13 – Cmorej et al. (2021) Life-Threatening Cyanide Intoxication after Ingestion of Amygdalin in Prehospital Care. Prehospital Emergency Care.
- 14 – Lerner (1981) Laetrile: A Lesson in Cancer Quackery. Ca-A Cancer Journal for Clinicians.