A peach pit is the hard shell, or stone, surrounding the seed, often called the kernel. This stone is a natural defense mechanism for the plant. While the fruit is safe to eat, the kernel contains naturally occurring chemical compounds. These compounds can become toxic upon ingestion, setting the stage for a biological process that releases a dangerous substance. This potential toxicity is why the pits of stone fruits, like peaches, cherries, and apricots, should not be consumed.
Identifying the Potential Hazard
The chemical compound responsible for the potential hazard is a cyanogenic glycoside known as amygdalin, which is highly concentrated within the soft kernel. Amygdalin is not toxic in its complete form, but it is classified as a cyanogen because it contains a nitrile group. This group is the structural component that can lead to the formation of a poison when the compound is broken down.
The hard outer shell of the peach pit acts as a protective barrier, preventing the amygdalin from being released. However, if the kernel is chewed or crushed, it is exposed to digestive enzymes, such as beta-glucosidase, present in the gut. Once this enzymatic reaction begins, amygdalin is hydrolyzed, or broken down, through a multi-step process.
This breakdown first forms prunasin, and then mandelonitrile, an unstable intermediate. The mandelonitrile then spontaneously decomposes into benzaldehyde and the highly toxic substance, hydrogen cyanide (HCN). This chemical process, called cyanogenesis, is the central mechanism by which the peach kernel becomes a toxic agent. The resulting hydrogen cyanide is quickly absorbed into the bloodstream, initiating a cascade of adverse physiological effects.
Recognizing the Signs of Poisoning
The danger of hydrogen cyanide lies in its ability to prevent the body’s cells from properly using oxygen, a process known as cellular asphyxiation. Cyanide binds to a specific enzyme within the mitochondria, cytochrome c oxidase, effectively shutting down the cell’s ability to produce energy. Since the entire body relies on this energy production, oxygen-dependent organs, such as the heart and brain, are quickly affected.
Symptoms of mild exposure, which typically occur with the ingestion of a single, chewed kernel, include headache and dizziness. The initial signs often involve gastrointestinal distress, such as nausea, vomiting, and abdominal pain. An individual may also experience rapid breathing and heart rate as the body attempts to compensate for the lack of oxygen being utilized by the cells.
More severe exposure, usually resulting from the consumption of multiple processed kernels, leads to far more serious symptoms. These high-level exposures can cause profound complications, including respiratory failure (the body’s inability to move sufficient oxygen into the blood). Seizures and a rapid, irregular heart rhythm are also common as the central nervous system begins to fail. The exposure can ultimately lead to a rapid drop in blood pressure, loss of consciousness, coma, and potentially death if not treated immediately.
Immediate Steps and Risk Assessment
The risk of poisoning is directly related to how the pit is consumed. Swallowing a whole peach pit poses a very low risk. The hard, outer shell is highly resistant to crushing and digestion, meaning the toxic kernel remains protected as it passes through the digestive tract. In this scenario, the whole pit is likely to exit the body without releasing a significant amount of amygdalin.
The risk increases substantially only if the inner kernel is chewed, crushed, or ground up before consumption, which allows the chemical reaction to occur. The amount of hydrogen cyanide required to cause acute toxicity in an average adult is estimated to be around 570 milligrams (mg). Since a single peach kernel contains a much smaller amount, typically around 2.2 mg of hydrogen cyanide per gram of seed, a single kernel is unlikely to cause serious harm.
It would take the consumption of multiple kernels, perhaps 30 or more for an adult, to reach a potentially lethal dose. The exact amount varies greatly based on the kernel’s concentration and the individual’s body weight. However, due to the unpredictability of kernel potency and individual sensitivity, particularly in small children, immediate action is necessary if a kernel is consumed. If a kernel has been chewed or processed, contact Poison Control immediately for guidance. The national hotline, 1-800-222-1222, provides expert, time-sensitive advice on the necessary steps to take.