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All plants contain tiny amounts of [https://en.wikipedia.org/wiki/Hydrogen_cyanide hydrogen cyanide] (HCN), however some plants also release high amounts of HCN from a class of glycosides called "cyanogenic glycosides". [https://en.wikipedia.org/wiki/Amygdalin Amygdalin] and [https://en.wikipedia.org/wiki/Linamarin linamarin] are common examples of cyanogenic glycosides. After being released from cyanogenic glycosides, HCN is highly toxic to animals. HCN boils at a relatively low temperature (25.6°C / 78.1°F). The human body is used to breaking down trace amounts of cyanide into the less toxic substance thiocyanate with an enzyme called rhodanese, which then leaves the body via urination <ref name="Gleadow_2014">[http://www.annualreviews.org/doi/full/10.1146/annurev-arplant-050213-040027 Cyanogenic Glycosides: Synthesis, Physiology, and Phenotypic Plasticity. Roslyn M. Gleadow and Birger Lindberg Møller. 2014.]</ref>. Although there are more than 3,000 plant species that are cyanogenic (a number of them cultivated by farmers perhaps because their cyanogenic properties deter animals from eating them), only a few parts of plants that are considered foods contain enough HCN from cyanogenic glycosides to be considered dangerous (generally, other forms of cyanide are considered more dangerous, such as from exposure to air or water that is polluted with cyanide) <ref name="CDC1">[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf toxicology Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Retrieved 08/25/2016.]</ref>. The location of the cyanogenic glycosides and the enzymes that release them are often each located in different (or all) parts of plants, and those locations are diverse across species. In some plants, the cyanogenic glycosides are concentrated in the stems or leaves of the plant and not the seeds (e.g. sorghum, barley, and lima beans). In fruits sometimes the seeds contain concentrated amounts (e.g. black cherry pits), and other times in the fruit itself (e.g. ''Passiflora edulis''). In rosaceous stone fruits, cyanogenic glycosides are located in the seeds, but the beta-glucosidase enzyme that the plant uses to release HCN is located in the roots of the plant. The concentration of cyanogenic glycosides is generally higher in seedling plants compared to mature plants, however this is there are a few exceptions where this is the opposite (e.g. some ''Eucalyptus'' species, and lima beans). HCN is released from cyanogenic glycosides just like other types of glycosides: beta-glucosidase enzyme or exposure to low pH breaks the bond between a glucose molecule and an unstable compound called "cyanohydrin" (or "alpha-hydroxynnitrile"), which then disassociates into a ketone or benzaldehyde and an HCN molecule. This reaction is stimulated by maceration, and by bacteria in the human gut. The cyanogenic glycosides themselves are not toxic until the HCN is released <ref name="Speijers">[http://www.inchem.org/documents/jecfa/jecmono/v30je18.htm "Cyanogenic Glycosides", First Draft. Dr G. Speijers. National Institute of Public Health and Environmental Protection Laboratory for Toxicology, Bilthoven, The Netherlands. Retrieved 08/25/2016.]</ref>.

Upon learning about cyanogenic glycosides, brewers often question the toxicity of cherry and apricot pits in beer. Assuming full conversion of these glycosides, and that none of the HCN boils off, levels of HCN introduced from cherry and apricot pits are too low to cause harm to adult humans. A lethal dosage of cyanide in humans is estimated to be around 1.52 mg per kilogram of body weight , with 0.56 mg per kilogram of body weight being the lowest recorded (although this lowest figure was obtained from a historical case when the measurements taken may not have been accurate) <ref>[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf toxicology Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Pg 42. Retrieved 08/25/2016.]</ref>. High exposure can cause harm to the brain and heart, and can cause comas or death. Exposure to 0.05 mg of cyanide per kilogram of body weight per day for 15-364 days is considered to cause accumulative health risks, such as reproductive, respiratory, neurological, thyroid, and gastrointestinal issues <ref>[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf toxicology Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Pg 21. Retrieved 08/25/2016.]</ref>. The EU regulates that alcoholic beverages cannot exceed 1 mg of HCN per ABV percentage (v/v%) per liter <ref>[http://ec.europa.eu/food/fs/sfp/addit_flavor/flav09_en.pdf COUNCIL DIRECTIVE of 22 June 1988 on the approximation of the laws of the Member States relating to flavourings for use in foodstuffs and to source materials for their production (88/388/EEC). The European Food Commission, Food Safety. Retrieved 08/26/2016</ref>. Luk Daenen, a glyoside researcher, calculated that for a 4% ABV alcohol beer, 4 mg of HCN per liter is allowed. With 200 grams of cherries per liter, and the pits being 10-14 grams of that weight, there is 22 - 30.8 amygdalin per liter of beer. This equates to 1.3 - 1.82 mg of HCN per liter of beer, which is less than the 4 mg of HCN per liter EU regulation. Considering that ~42 mg of HCN is required to kill a person that weighs 70 kilograms (154 pounds), that person would need to drink around 23 liters of beer <ref>[https://www.uclouvain.be/cps/ucl/doc/inbr/documents/presentation-luk-daenen.pdf "Use of beta-glucosidase activity for flavour enhancement in specialty beers," slideshow by Luk Daenen. 2012. Retrieved 08/26/2016.]</ref>. 350 mL of alcohol would kill a 70 kilogram adult <ref>[http://www.alcohol.org.nz/alcohol-its-effects/health-effects/alcohol-poisoning "Alcohol Poisoning". NZ Health Promotion Agency. Retrieved 08/26/2016.]</ref>. The amount of 4% ABV beer required to kill a 70 kg adult from alcohol poisoning is around 8.75 liters. Alcohol would kill such a person far before cyanide poisoning would become a concern.