The Chemical Culprit: Solanine and Chaconine
Potatoes are part of the Solanum genus, a family of plants that also includes tomatoes, eggplants, and deadly nightshade. These plants produce compounds known as glycoalkaloids as a natural defense mechanism against pests, disease, and predators. The two primary glycoalkaloids found in potatoes are α-solanine and α-chaconine. While typically present in low and harmless amounts, their concentration can increase significantly under certain conditions, making the potato bitter and potentially harmful if consumed.
How Potato Glycoalkaloids Form
Glycoalkaloid levels in a potato are directly influenced by its environment. Exposure to sunlight is a major factor that stimulates the production of both chlorophyll, which causes the potato to turn green, and glycoalkaloids. The green color is a useful visual indicator of potential toxicity, although the color and the toxin are produced independently. Other factors that cause an increase in these toxins include mechanical damage, improper storage conditions (such as high temperatures), and sprouting. Immature potatoes also tend to have higher concentrations of glycoalkaloids.
Symptoms of Glycoalkaloid Poisoning
Symptoms of solanine and chaconine poisoning can be both gastrointestinal and neurological, typically appearing 8 to 12 hours after ingestion but sometimes as quickly as 10 minutes.
- Gastrointestinal effects: Nausea, vomiting, diarrhea, stomach cramps, and a burning sensation in the throat.
- Neurological effects: Headaches, dizziness, dilated pupils, fever, hallucinations, and in severe cases, paralysis and loss of sensation.
In rare but severe cases, high levels of glycoalkaloids can be fatal, although most people who experience poisoning recover fully.
Practical Steps for Safe Potato Consumption
To minimize the risk of glycoalkaloid exposure, it is crucial to handle and prepare potatoes correctly. Fortunately, these toxins are often concentrated in the parts of the potato that can be removed.
Proper Storage and Handling
Proper storage is the first line of defense against elevated glycoalkaloid levels. Potatoes should be stored in a cool, dark, and well-ventilated area. Avoid storing them in direct sunlight or in the refrigerator, as cold temperatures can also increase their sugar content, which can lead to higher acrylamide levels during cooking. Brown paper bags or burlap sacks are ideal for storing potatoes as they protect them from light exposure.
Preparation Methods to Reduce Toxicity
While cooking methods do not completely destroy glycoalkaloids, proper preparation can significantly reduce their concentration.
- Peeling: Since the highest concentration of solanine is in and just beneath the skin, peeling the potato can reduce the glycoalkaloid content by 25–75%.
- Trimming: Always trim away any green parts, sprouts, or "eyes" from the potato generously, as these areas contain the most toxins.
- Discarding Bitter Potatoes: The presence of high glycoalkaloid levels gives potatoes a bitter taste. If a potato tastes bitter after cooking, it should be discarded.
Comparison of Glycoalkaloids in Different Potato Parts
| Feature | Potato Flesh | Potato Peel and Sprouts |
|---|---|---|
| Glycoalkaloid Concentration | Typically very low | Significantly higher, especially when green or sprouted |
| Safety for Consumption | Safe for consumption under normal conditions | Potentially toxic; should be removed |
| Effect of Light Exposure | Minimal change if skin is removed | Production of glycoalkaloids increases dramatically with light exposure |
| Taste | Neutral, starchy | Often bitter, a sign of toxicity |
Historical Context and Regulatory Measures
Glycoalkaloid poisoning is not a modern phenomenon, with historical records of outbreaks linked to potatoes with high toxin levels. Incidents have occurred in various parts of the world, including mass poisonings at a school in the UK and in Canada. In response, regulatory bodies in many countries, such as the EU and Canada, have established maximum safety levels for total glycoalkaloids in commercial potatoes. This ensures that the potatoes sold in grocery stores are generally safe for consumption, provided they are handled properly at home.
Conclusion
What drug is in potatoes? The answer is not a drug in the recreational sense but a natural plant toxin called glycoalkaloid, with solanine and chaconine being the primary types. While perfectly safe in normal potatoes, these compounds can reach dangerous levels in green, damaged, or sprouting potatoes. By practicing proper storage—in a cool, dark place—and preparing potatoes correctly—by peeling and trimming any green or sprouted parts—consumers can easily mitigate any health risks. A potato's bitter taste is the most reliable sign that it is unsafe to eat, providing a simple yet crucial warning from nature.
Visit this USDA article for more information on green potatoes and food safety.
