Plum pits contain Amygdalin, a cyanogenic glycoside that is present in the pits of many stone fruits, including plums, peaches, and cherries. The danger is not from the whole, intact pit, but specifically from the inner kernel being crushed, chewed, or ground. Swallowing a plum pit whole is generally not a concern, as the hard outer shell prevents the toxic compound from being released and absorbed in the digestive system. The risk is directly tied to physically breaking the pit, which releases the chemical mechanism that produces poison.
The Chemical Mechanism of Toxicity
The toxic potential of a plum pit lies in the presence of Amygdalin. This compound is stored safely within the pit’s kernel and is non-toxic in its intact form. Toxicity begins when the pit is crushed or chewed, causing the Amygdalin to mix with specific enzymes, such as beta-glucosidase, present within the seed or the human digestive tract.
This contact initiates a chemical reaction called hydrolysis, which rapidly breaks down the Amygdalin. The final and most dangerous product of this breakdown is hydrogen cyanide (HCN) gas, a fast-acting poison. Cyanide is harmful because it interferes with the body’s ability to use oxygen at the cellular level. Specifically, it inhibits the enzyme cytochrome oxidase, which is an integral part of cellular respiration. This essentially starves the body’s cells of oxygen, leading to rapid systemic failure.
Determining a Dangerous Dose
Providing a precise number of plum pits that would constitute a dangerous dose is almost impossible due to significant biological and chemical variability. The concentration of Amygdalin differs widely based on the specific species of plum, its ripeness, and environmental factors during growth, with some varieties containing as much as 17.5 milligrams per gram of kernel. Furthermore, the amount of hydrogen cyanide released from Amygdalin can vary depending on individual factors, such as body weight, metabolism, and the presence of certain gut bacteria that aid in the conversion process.
The lethal dose of pure cyanide in humans is estimated to be between 0.5 and 3.5 milligrams per kilogram of body weight. A rough estimate suggests that one average-sized crushed plum pit kernel can potentially yield about 6 milligrams of hydrogen cyanide. For an average adult, this means that severe toxicity would likely require ingesting and thoroughly chewing the kernels from several to many pits.
While one crushed pit is unlikely to be lethal for an adult, it can still cause mild symptoms. The risk increases dramatically for children or smaller adults due to the lower body weight. For example, the ingestion of just a few crushed kernels from related Prunus species, like apricot, has been documented to cause severe poisoning in children.
Symptoms and Emergency Response
Symptoms of acute cyanide poisoning from ingesting crushed plum pits can manifest quickly, often within minutes to a few hours of exposure. Mild poisoning may initially present as non-specific symptoms such as headache, dizziness, nausea, and vomiting. These early signs can be mistaken for simple food poisoning or an upset stomach, making accurate assessment difficult.
As the dose of cyanide absorbed increases, the symptoms become more severe, reflecting the body’s inability to utilize oxygen. These signs include rapid breathing, confusion, significant weakness, and a rapid or slow heart rate. In cases of severe exposure, the individual may experience seizures, loss of consciousness, dangerously low blood pressure, and ultimately, cardiac arrest. A subtle, though not always present, sign is a distinct, bitter almond odor on the breath.
If the ingestion of crushed or chewed plum pits is suspected, it is imperative to seek immediate emergency medical attention. The first step should be to contact Poison Control or your local emergency services immediately for professional guidance. If a whole, intact pit was swallowed, the risk is low, but if the pit was chewed, blended, or ground, the potential for toxicity is much higher and requires prompt action.