Cherries, a widely enjoyed stone fruit, contain a hard center that is commonly referred to as the cherry pit. Botanically, this pit is known as the endocarp, a hardened layer of the fruit wall that encloses the true seed, or kernel, inside. The presence of this stone is what classifies the cherry as a drupe, a type of fruit that also includes peaches, plums, and apricots.
The Physical Components of a Cherry Pit
The structure of a cherry pit consists of two main parts: the rigid outer shell and the small kernel housed within. The shell, or endocarp, is composed mainly of indigestible fibers like lignin, cellulose, and hemicellulose, giving it a dense, woody texture that resists breakdown. This fibrous exterior accounts for a significant portion of the pit’s mass.
The inner kernel, the actual seed, contains a variety of compounds that are typical of many plant seeds. It is rich in oils, proteins, and fiber. Cherry kernel oil, which is sometimes extracted for use in cosmetics, is particularly high in unsaturated fatty acids, such as oleic and linoleic acids. The kernel also contains carbohydrates and minerals like potassium, phosphorus, and calcium.
The hard shell’s primary function is physical protection, shielding the delicate kernel from external damage and digestive processes. The toxic compounds are stored within the kernel, not the outer shell, and are only problematic if the seed is cracked open.
Amygdalin: The Chemical Compound Inside
The kernel holds a chemical compound called amygdalin, which belongs to a group known as cyanogenic glycosides. A glycoside is a molecule where a sugar is bonded to a non-sugar chemical group, and the cyanogenic part indicates its potential to release hydrogen cyanide. Amygdalin is a naturally occurring plant defense mechanism also found in the seeds of other stone fruits like peaches and apricots.
In the plant, the amygdalin molecule is stored separately from the enzymes required to break it down. This physical separation ensures the compound remains stable and non-toxic unless the seed is damaged. When the seed tissue is crushed, the amygdalin and the enzymes mix, initiating a chemical cascade.
The concentration of amygdalin can vary significantly depending on the cherry variety. Although amygdalin itself is not toxic, its structure contains a nitrile group that is the precursor to the harmful substance. This chemical is not a vitamin, despite being historically mislabeled as “Vitamin B17” or laetrile in some alternative medicine contexts.
Understanding Cyanide Toxicity
The danger arises when the cherry pit is chewed or crushed, allowing the amygdalin to come into contact with specific enzymes present in the seed and the digestive tract. This enzymatic action hydrolyzes the amygdalin, breaking it down in a multi-step process that ultimately releases hydrogen cyanide (HCN). Hydrogen cyanide is a rapid-acting poison that interferes with the body’s ability to use oxygen at the cellular level.
The dose of cyanide determines the severity of the poisoning. Acute toxicity can occur at doses as low as 0.5 to 3.5 milligrams per kilogram of body weight. This toxin primarily targets organs that require a high amount of oxygen, such as the brain, heart, and lungs, by inhibiting a key enzyme in the energy production pathway.
The risk is significantly lower if a cherry pit is swallowed whole and intact. The tough, hard shell of the endocarp prevents the amygdalin from mixing with the enzymes, and the pit typically passes harmlessly through the digestive system. However, if multiple pits are chewed or ground up, the risk of poisoning increases, particularly for children due to their lower body weight.
Mild symptoms of exposure include headache, dizziness, heightened anxiety, and vomiting. More serious signs involve rapid breathing, increased heart rate, seizures, confusion, and respiratory failure. Individuals who accidentally chew multiple pits should monitor themselves for adverse symptoms and contact a poison control center.