Potato flowers are often overlooked, but they are poisonous. Like the fruit, leaves, and stems of the plant, the flowers contain naturally occurring toxins that can be harmful if consumed.
The potato plant, Solanum tuberosum, belongs to the Solanaceae family, commonly known as the nightshades, which also includes tomatoes and eggplants. This toxicity is an evolved strategy to protect the plant from pests and grazing animals.
Identifying the Toxic Compound
The toxicity in the potato plant is due to a class of compounds called glycoalkaloids, which are nitrogen-containing compounds. The two most prevalent types are alpha-solanine and alpha-chaconine. These compounds are naturally produced by the plant as a defense mechanism against insects, fungi, and pathogens.
Glycoalkaloids are steroid-like compounds synthesized from cholesterol. Alpha-chaconine and alpha-solanine typically account for over 95% of the total glycoalkaloid content. They work synergistically to protect the plant tissue and impart a bitter taste when present in high concentrations.
Where Toxicity Levels Are Highest
While potato flowers are toxic, they are not the most concentrated source of glycoalkaloids. The highest levels are typically found in the potato’s sprouts, or “eyes,” which can contain up to 997 milligrams per 100 grams of fresh weight in some varieties. Leaves and stems, the parts of the plant above ground, also contain high concentrations.
The potato tuber is safe to consume under normal conditions, but light exposure triggers a defensive response. When a tuber is exposed to light, it produces chlorophyll, causing it to turn green just under the skin. This green color indicates a concurrent, significant increase in glycoalkaloid production. A greened tuber can contain ten to twenty times the amount of toxins found in a normal potato.
Symptoms of Glycoalkaloid Poisoning
Ingesting plant parts with elevated glycoalkaloid levels can lead to symptoms of poisoning in humans. The initial and most common effects are gastrointestinal, typically appearing between 30 minutes and 12 hours after consumption. Symptoms include nausea, vomiting, abdominal cramps, and diarrhea.
Higher doses affect the nervous system, leading to neurological symptoms. These may include headaches, drowsiness, confusion, or weakness. A toxic dose is generally considered to be around 1 to 2 milligrams of total glycoalkaloids per kilogram of body weight. If severe symptoms like confusion, rapid pulse, or high fever occur, immediate medical attention is necessary.
Handling Potatoes Safely
Consumers can take steps to minimize the risk of glycoalkaloid exposure. Proper storage is the primary method of prevention, as light exposure triggers increased toxin production. Potatoes should be kept in a cool, dark, and dry area, ideally between 45 and 50 degrees Fahrenheit.
The skin contains the highest concentration of glycoalkaloids, so peeling is an effective safety practice. Peeling can reduce the total glycoalkaloid content by 25 to 75%. Any potatoes that have turned green, started to sprout, or taste bitter should be discarded entirely, as the toxins can sometimes penetrate deeper than the skin layer.