Amygdalin, often marketed as “vitamin B17,” is found mainly in the seeds and kernels of stone fruits like apricots, peaches, plums, and cherries, as well as in bitter almonds and apple seeds. It is not actually a vitamin, and eating these foods in their usual forms (the fruit flesh, not the seeds) poses no risk. The safety concern kicks in when people deliberately eat the seeds or kernels, or take concentrated amygdalin supplements, because the compound breaks down into hydrogen cyanide inside the body. That process, and how much of these foods it takes to cause harm, is where the story gets more complicated than most wellness blogs suggest.
Which Foods Contain Amygdalin
Amygdalin is a cyanogenic glycoside, meaning it belongs to a family of plant compounds that can release cyanide when broken down. It occurs naturally in the seeds of many plants in the Rosaceae family, which includes most stone fruits and pome fruits.1PubMed Central. Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds The fruit flesh you eat when you bite into a peach or plum is fine. The amygdalin lives in the seed inside the pit, or in the kernel you would have to crack the pit open to reach.
The richest dietary source, by a wide margin, is bitter apricot kernels. Laboratory analysis of commercially available products found that bitter apricot kernel products contained amygdalin at concentrations between about 5,500 and 24,000 micrograms per gram. Sweet apricot kernel products, by contrast, contained only 31 to 296 micrograms per gram.2Journal of AOAC INTERNATIONAL. Determination of Amygdalin in Apricot Kernels and Almonds Using LC-MS/MS That is a difference of roughly two orders of magnitude, so the distinction between bitter and sweet varieties matters enormously.
A UK-based survey of seeds, kernels, and food products found that Rosaceae species in general contained relatively high amounts of amygdalin, ranging from about 0.1 to 17.5 milligrams per gram of seed, while non-Rosaceae seeds measured far lower, in the range of 0.01 to 0.2 milligrams per gram.3PubMed. Amygdalin content of seeds, kernels and food products commercially-available in the UK Apple and plum seeds also contain cyanogenic glycosides, though their edible fruit flesh does not pose a concern.4PubMed. Dynamics of cyanogenic glycosides in apple and plum fruits, products, and byproducts: A concise review
Here is a rough ranking of common foods by their amygdalin content in the seed or kernel:
- Bitter apricot kernels: by far the highest, up to 24 mg/g
- Bitter almonds: high, typically in the same general range as bitter apricot kernels
- Peach, plum, and cherry pits: moderate to high, within the broader Rosaceae range
- Apple seeds: present but at lower concentrations per seed, and each seed is small
- Sweet almonds and sweet apricot kernels: much lower, often under 300 µg/g
The sweet almonds you buy at a grocery store are not the same as bitter almonds. Sweet almonds have very low amygdalin content and are safe to eat in normal quantities. Bitter almonds, which have a sharply astringent taste, are a different cultivar with much higher amygdalin levels. In many countries, raw bitter almonds are restricted or banned from retail sale for exactly this reason.
Why Bitter Varieties Have So Much More
The enormous gap between bitter and sweet varieties comes down to enzyme activity inside the plant. Bitter cultivars of both apricot kernels and almonds have lower activity of an enzyme called beta-glucosidase, which normally breaks down amygdalin within the plant tissue itself. Because the enzyme is less active in bitter genotypes, amygdalin accumulates to much higher levels.2Journal of AOAC INTERNATIONAL. Determination of Amygdalin in Apricot Kernels and Almonds Using LC-MS/MS Sweet varieties have more of this enzyme, so they break down their own amygdalin before it can accumulate. The bitterness you taste is actually a signal: the more bitter the kernel, the more amygdalin it contains.
How Amygdalin Turns Into Cyanide
On its own, amygdalin is a stable molecule. It does not release cyanide just sitting in a seed. The danger begins when it is broken down. Enzymatic hydrolysis of the compound’s sugar linkage produces a short-lived intermediate called a cyanohydrin, which then rapidly falls apart into benzaldehyde and hydrogen cyanide (HCN).5PubMed Central. Photo-amygdalin: light-dependent control over hydrogen cyanide release and cytotoxicity That hydrogen cyanide is the toxic product. The benzaldehyde, incidentally, is what gives bitter almonds their characteristic scent.
Early proponents of amygdalin as a cancer therapy claimed that this breakdown happened selectively inside tumor cells. That idea has not held up. Research has shown that HCN is released in normal cells too, which is a core reason the compound is not safe as a therapeutic agent.1PubMed Central. Amygdalin: Toxicity, Anticancer Activity and Analytical Procedures for Its Determination in Plant Seeds
Your Gut Bacteria Are the Main Problem
One of the more surprising aspects of amygdalin toxicity is that your gut microbiome does most of the dirty work. When amygdalin is given intravenously, studies have found little to no hydrogen cyanide formation. But when it is swallowed, the bacteria in the intestines break it down aggressively. The Bacteroidetes group of gut bacteria, in particular, has high beta-glucosidase activity and can efficiently convert amygdalin into HCN.6PubMed Central. Effects of the Gut microbiota on Amygdalin and its use as an anti-cancer therapy: Substantial review on the key components involved in altering dose efficacy and toxicity
An elegant experiment demonstrated this directly. When conventional rats with normal gut bacteria received a single oral dose of amygdalin at 600 mg per kilogram of body weight, they often became lethargic, had convulsions, and usually died within two to five hours, with high blood cyanide levels. Germ-free rats given the exact same dose showed no symptoms and had blood cyanide levels indistinguishable from untreated animals. Only the rats with intestinal bacteria were at risk.7Biochemical Pharmacology. Role of the gastrointestinal microflora in amygdalin (laetrile)-induced cyanide toxicity The takeaway is stark: oral ingestion is far more dangerous than other routes of exposure because the gut microbiome acts as a cyanide-generating factory.
This also means that individual differences in gut bacteria composition could affect how much cyanide a given person produces from a set amount of amygdalin. Your body does have a built-in cyanide detoxification system involving an enzyme called rhodanese (thiosulfate-cyanide sulfurtransferase), which converts cyanide to the much less toxic thiocyanate.8PubMed Central. Thiosulfate-Cyanide Sulfurtransferase a Mitochondrial Essential Enzyme: From Cell Metabolism to the Biotechnological Applications But this system can be overwhelmed if cyanide is released faster than the enzyme can process it. There is even evidence of genetic variation in rhodanese activity across people, meaning some individuals may be more vulnerable than others to the same dose.9PubMed. Evidence for a functional genetic polymorphism of the human thiosulfate sulfurtransferase (Rhodanese), a cyanide and H2S detoxification enzyme
How Much Is Considered Safe
The European Food Safety Authority (EFSA) established an acute reference dose for cyanide of 20 micrograms per kilogram of body weight.10PubMed Central. Evaluation of the health risks related to the presence of cyanogenic glycosides in foods other than raw apricot kernels For a person weighing around 70 kilograms (about 154 pounds), that works out to a cyanide limit of 1,400 micrograms, or 1.4 milligrams. Given that bitter apricot kernels can contain several milligrams of releasable cyanide per kernel, eating just a handful could theoretically exceed this threshold.
One case report estimated that each apricot kernel consumed by a poisoning victim would have contained cyanide concentrations averaging about 2.9 milligrams per gram.11PubMed Central. Hydroxocobalamin treatment of acute cyanide poisoning from apricot kernels A single large bitter apricot kernel weighs roughly half a gram to a gram, so a few kernels can deliver a dose that exceeds the EFSA safety reference for an adult. Children, with their lower body weight, are at proportionally greater risk from even smaller numbers of kernels.
Some countries have responded to these risks with specific regulations. The European Union, for instance, has set maximum levels for hydrocyanic acid in certain foods. Australia and New Zealand have issued guidance limiting raw apricot kernel consumption. The United States has not set a formal limit on raw kernel sales, though the FDA has taken enforcement action against products marketed as cancer treatments.
Can Processing Make These Foods Safer
Yes, and this matters because many traditional cuisines around the world use bitter almonds or apricot kernels in cooking, often after treatment that reduces the cyanide risk. Grinding, soaking, and cooking bitter apricot seeds have all been shown to significantly degrade amygdalin and its toxic breakdown products, reducing total cyanogenic potential from high starting levels down to much lower concentrations.12Food Chemistry. The effects of grinding, soaking and cooking on the degradation of amygdalin of bitter apricot seeds
Among processing methods studied for apricot kernels, roasting appears to be one of the most effective single-step treatments. One study found that roasting at 160°C for ten minutes reduced the amygdalin content of bitter apricot kernels from about 27.6 mg/g down to roughly 9.8 mg/g, a reduction of about two-thirds.13İnönü Üniversitesi Sağlık Hizmetleri Meslek Yüksekokulu Dergisi. The Effect of Different Processing Methods on Amygdalin Levels and Some Physicochemical Properties of Apricot Kernels For bitter almond oil, more intensive methods like water boiling and ultrasonic treatment achieved cyanide reductions above 98%.14International Journal of Food Science & Technology. Reduction of cyanide content of bitter almond and its oil using different treatments
Soaking in water is one of the oldest and simplest approaches. The cyanide-containing breakdown products are water-soluble, so prolonged soaking followed by discarding the water removes a substantial portion. Many traditional Mediterranean and Middle Eastern preparations of bitter almonds involve extended soaking and multiple water changes. The risk comes when people eat raw, unprocessed bitter kernels, which is precisely the scenario in most poisoning cases.
The “Vitamin B17” Cancer Claim
Amygdalin was rebranded as “vitamin B17” and “laetrile” in the 1950s and promoted as a natural cancer cure. The hypothesis was that cancer cells contained a specific enzyme that would preferentially break down amygdalin and release cyanide locally, killing the tumor while leaving healthy tissue untouched. This idea attracted a large following in alternative medicine communities and led to a wave of patients seeking amygdalin treatment, particularly at clinics in Mexico after it was restricted in the United States.
The evidence has not supported these claims. A Cochrane systematic review, which is the gold standard for evaluating medical treatments, found no sound clinical data supporting beneficial effects for cancer patients. The review stated plainly that the risk-benefit balance is “unambiguously negative,” given the real danger of cyanide poisoning and the absence of demonstrated anti-cancer benefit.15PubMed Central. Laetrile treatment for cancer
It is also worth noting that amygdalin is not a vitamin by any scientific definition. Vitamins are essential nutrients that the body cannot produce in adequate quantities and must obtain from food. There is no known metabolic requirement for amygdalin, and no deficiency disease results from not consuming it. The “vitamin B17” label was a marketing strategy, not a nutritional classification. No major nutrition or medical organization recognizes it as a vitamin.
Poisoning Cases and What They Look Like
Published case reports paint a clear picture of what amygdalin poisoning looks like. A 35-year-old woman who ate more than 20 raw apricot kernels initially appeared asymptomatic but about 70 minutes after ingestion developed headache, nausea, difficulty breathing, low blood pressure, and dangerously low oxygen levels.11PubMed Central. Hydroxocobalamin treatment of acute cyanide poisoning from apricot kernels The delay is characteristic: oral amygdalin takes time to reach the gut bacteria that convert it to cyanide, so there can be a deceptive window where the person feels fine.
Children are at particular risk. A 4-year-old boy with cancer whose parents had been giving him intravenous and oral “vitamin B17” along with apricot kernels as an alternative treatment arrived at an emergency department severely unresponsive, with a Glasgow Coma Scale score of 3 (the lowest possible) and severe metabolic acidosis from cyanide poisoning. He recovered after treatment with sodium thiosulfate, but the case illustrates how dangerous these products can be, especially at pediatric body weights.16PubMed. Severe cyanide poisoning from an alternative medicine treatment with amygdalin and apricot kernels in a 4-year-old child
Concentrated amygdalin tablets are arguably even riskier than raw kernels because they deliver a more standardized, higher dose. A 73-year-old woman with metastatic pancreatic cancer developed cyanide toxicity from amygdalin tablets and required emergency treatment with hydroxocobalamin.17PubMed Central. Physician Beware: Severe Cyanide Toxicity from Amygdalin Tablets Ingestion The common thread across these cases is cancer patients turning to amygdalin out of desperation, often while foregoing or delaying proven treatments.
Emergency Treatment for Cyanide Poisoning
If someone does ingest a dangerous amount of amygdalin, two well-established antidotes exist: hydroxocobalamin (a form of vitamin B12) and sodium thiosulfate. They work through different mechanisms. Hydroxocobalamin binds directly to cyanide in the bloodstream and acts quickly. Sodium thiosulfate enhances the body’s own rhodanese-mediated detoxification pathway, converting cyanide to thiocyanate, but acts more slowly.18PubMed Central. Acute Cyanide Poisoning: Hydroxocobalamin and Sodium Thiosulfate Treatments with Two Outcomes following One Exposure Event The combination can be more effective than either alone, since hydroxocobalamin provides rapid initial protection while sodium thiosulfate offers more sustained cyanide clearance.19PubMed. Successful Use of Hydroxocobalamin and Sodium Thiosulfate in Acute Cyanide Poisoning: A Case Report with Follow-up
The challenge is recognizing cyanide poisoning in time. Emergency physicians may not immediately suspect it unless they are told about apricot kernel or amygdalin supplement use, because the initial symptoms (headache, nausea, confusion, rapid heart rate) overlap with many other conditions. The delayed onset after oral ingestion adds another layer of difficulty. Anyone who has eaten raw bitter kernels or amygdalin supplements and begins to feel unwell should tell medical staff exactly what they consumed and how much.
Other Cyanogenic Foods Worth Knowing About
Amygdalin gets most of the attention, but it is just one member of a large family. Thousands of plant species produce cyanogenic glycosides. Cassava, a staple food for hundreds of millions of people in tropical regions, contains linamarin and lotaustralin rather than amygdalin. Cassava leaves have the highest concentrations (around 5 grams of linamarin per kilogram of fresh weight), while roots contain roughly 20 times less, with total levels ranging from about 100 to 500 milligrams per kilogram depending on the cultivar.20PubMed Central. Cyanogenesis in Cassava: The Role of Hydroxynitrile Lyase in Root Cyanide Production Lima beans, sorghum, and white clover also produce cyanogenic glycosides.
Traditional cassava preparation, which involves peeling, soaking, fermenting, and thorough cooking, is specifically designed to reduce cyanogenic glycoside content to safe levels. Communities that depend on cassava have developed these methods over centuries. Problems arise when cassava is improperly processed, which continues to cause outbreaks of cyanide-related illness in some regions. The parallel to bitter apricot kernels is direct: the raw plant material is potentially dangerous, but proper processing makes it safe. The foods most likely to cause harm are those consumed raw, in concentrated supplement form, or without traditional preparation methods that evolved to manage exactly this risk.