Eating a raw or partially cooked potato is generally unsafe due to two distinct problems: the presence of natural toxic compounds and the indigestible nature of the raw starch itself. While fully cooked potatoes are nutritious, undercooking them fails to eliminate these inherent biological defenses. The severity of the reaction depends on the amount consumed and the condition of the potato prior to cooking.
Understanding Glycoalkaloids and Toxicity
Potatoes naturally contain a group of toxic compounds known as glycoalkaloids, primarily alpha-solanine and alpha-chaconine, as the plant’s defense mechanism. These compounds are present in all potatoes, but typically at levels below the generally accepted safety limit of 20 milligrams per 100 grams of fresh potato. Glycoalkaloids are concentrated most heavily in the skin, sprouts, and any areas that have turned green or been damaged.
Exposure to sunlight or improper storage conditions causes the potato to synthesize more of these toxins, often indicated by the green coloring just beneath the skin. The green color itself is chlorophyll, but its presence is a visual warning sign that glycoalkaloid concentration has likely increased. A bitter or acrid taste in the potato is a more direct indicator of dangerously high toxin levels.
Consuming potatoes with elevated levels of glycoalkaloids can lead to a condition known as potato poisoning. Mild to moderate symptoms usually appear within a few hours and include gastrointestinal distress such as nausea, vomiting, abdominal pain, and diarrhea. This is because the toxins disrupt cell membranes in the digestive system.
In more severe cases, neurological symptoms can occur. These can include headaches, drowsiness, confusion, and in extremely rare instances, paralysis or even death. The toxic dose is estimated to be around two milligrams of glycoalkaloids per kilogram of body weight, which highlights why removing sprouts and green parts is a necessary step before cooking.
Digestive Challenges of Raw Potato Starch
The physical structure of raw potato starch makes it difficult for the human digestive system to process. Potato starch in its uncooked state is a form of resistant starch, meaning it resists breakdown by human digestive enzymes like amylase in the small intestine. Cooking is required to break down this structure.
The undigested starch then passes into the large intestine, where it is fermented by gut bacteria. This fermentation causes common symptoms associated with eating raw or undercooked potatoes, such as bloating and excessive gas. Depending on the amount consumed, this can also lead to stomach cramps and diarrhea.
The symptoms of gastrointestinal upset from resistant starch are distinct from glycoalkaloid poisoning, but can still cause significant discomfort. Cooking the potato changes the starch structure through a process called gelatinization, which makes it easily digestible. This process is what transforms the hard, chalky texture of a raw potato into the soft, mealy texture of a cooked one.
Proper Storage and Cooking to Ensure Safety
Preventing glycoalkaloid accumulation starts with proper storage. Potatoes should be stored in a cool, dark, and well-ventilated location, ideally between 45 and 50 degrees Fahrenheit. Storing them in a dark place prevents exposure to light, which triggers the formation of chlorophyll and the associated rise in glycoalkaloid levels.
It is also important to store potatoes away from ethylene-producing fruits like apples and onions, as the gas released by these items can accelerate sprouting. Before cooking, any visible sprouts, eyes, or green sections should be cut away completely and discarded, as these areas concentrate the toxins. Peeling the potato can remove 30 to 80% of the glycoalkaloids that reside close to the surface.
Cooking is the final step to ensure safety, primarily by making the starch digestible. While heat does not completely destroy glycoalkaloids—boiling, for instance, only minimally reduces the concentration—it does make the potato safe by gelatinizing the starch. A potato is fully cooked when it is uniformly fork-tender throughout, confirming the starch has fully gelatinized and the entire tuber is safe to eat.