The common fear that a swallowed seed will germinate and sprout inside the body is a widespread misconception that lacks scientific basis. The human body is well-equipped to handle most ingested seeds, which are not exposed to the necessary light, soil, or sustained environmental conditions required for growth. The digestive system treats most seeds as a form of dietary fiber, processing them safely through the gastrointestinal tract.
The Digestive Journey
When a seed is swallowed whole, its fate is determined by the tough outer layer known as the seed coat. This protective layer is composed of cellulose, a complex carbohydrate that the human digestive system cannot break down. Humans lack the necessary enzyme, cellulase, meaning the seed’s internal contents remain shielded from digestive acids and enzymes.
The seed travels through the stomach and small intestine, where mechanical churning and chemical agents work on surrounding material. Since the cellulose coat remains intact, the seed is not absorbed and provides no nutritional value. Small seeds, like those found in kiwis, strawberries, or tomatoes, become part of the roughage that aids in intestinal movement. The seed continues its transit into the large intestine and is eventually excreted, often entirely whole, as part of a bowel movement.
Toxicity Concerns
While most seeds are harmless fiber, a few common fruit pits and seeds contain compounds that pose a chemical risk if processed improperly. The seeds of stone fruits, such as cherries, apricots, peaches, and apples, contain cyanogenic glycosides, primarily amygdalin. This compound is not toxic when protected within the whole seed.
Toxicity arises when the seed is crushed or chewed, which releases the amygdalin and exposes it to specific enzymes. This enzymatic reaction converts the amygdalin into hydrogen cyanide, a potent poison. Swallowing a few whole apple seeds or a single cherry pit is safe because the hard seed coat prevents the release of the toxin. A significant quantity of crushed seeds is required to release a dangerous dose of cyanide. The acute lethal dose is estimated to be around 0.5 to 3.5 milligrams per kilogram of body weight.
When to Seek Medical Attention
While the body handles most seeds without incident, acute situations require immediate medical attention. The most immediate physical danger is aspiration, where a seed is accidentally inhaled into the lungs instead of being swallowed down the esophagus. Symptoms of aspiration include sudden, severe coughing, difficulty breathing, or turning blue, which constitutes an emergency airway obstruction.
A very large seed or a massive collection of small seeds can, in rare cases, lead to an intestinal obstruction, also called a bezoar. This is more likely with large pits or in individuals with pre-existing digestive issues. Symptoms of an intestinal blockage include severe, crampy abdominal pain, persistent vomiting, abdominal swelling, or the inability to pass gas or stool. Signs of acute poisoning from crushed toxic seeds, such as dizziness, rapid heart rate, confusion, or lightheadedness, also require emergency care.