Which Potatoes Have the Most Solanine? A Guide to Food Safety

Potatoes naturally produce solanine, a toxic glycoalkaloid, as a defense mechanism, but its concentration can increase significantly under certain conditions. While no single commercial variety reliably has the most solanine, the highest levels are consistently found in potatoes that have turned green, are sprouting, or have been improperly stored.

Quick Summary

This guide explains which potatoes pose the highest risk of solanine toxicity by detailing the environmental factors that cause elevated levels. It covers how to identify, prevent, and handle high-solanine potatoes to ensure food safety and avoid potential health issues.

Key Points

• Green Potatoes: The most common and reliable indicator of high solanine is a potato that has turned green due to light exposure.

• Sprouts and Damage: High concentrations of solanine and other glycoalkaloids are found in sprouts (eyes) and around any physically damaged areas.

• Improper Storage: Factors like light exposure, extreme temperatures, and age significantly increase solanine levels, regardless of potato variety.

• Wild vs. Commercial: While modern commercial potatoes are bred for low solanine, older or wild potato species can contain much higher, dangerous levels.

• Peel, Trim, and Taste: To reduce risk, always peel green potatoes and remove sprouts. If a potato tastes bitter, it has high solanine and should be discarded.

Understanding Solanine in Potatoes

Solanine is a naturally occurring defense compound produced by the potato plant (Solanum tuberosum) to protect itself from pests, disease, and predators. In properly grown and stored potatoes, the levels are minimal and generally harmless to humans. However, certain stressors can cause a dramatic increase in glycoalkaloid synthesis, concentrating the toxin in specific parts of the tuber. It is important to note that solanine is concentrated in the peel and the underlying green layer, but elevated levels can also extend deeper into the potato flesh.

The Role of Greening, Sprouting, and Damage

The most significant factor influencing solanine levels is the potato's state, not its variety. When a potato is exposed to light, it begins to produce chlorophyll, which causes the skin to turn green. This greening is a visual cue that the production of solanine has also been stimulated, although the two processes are not directly linked. Green potatoes have been shown to contain up to seven times more solanine than non-illuminated ones, making them a primary concern.

Similarly, sprouts (or "eyes") and damaged areas of a potato also contain high concentrations of glycoalkaloids. The plant prioritizes protecting new growth, and mechanical damage triggers a protective response that increases toxin production.

Factors Causing High Solanine Concentrations

• Light Exposure: Storing potatoes in direct sunlight or under fluorescent lights is the most common cause of greening and subsequent solanine increase. The intensity and duration of light exposure directly correlate with higher levels.
• Improper Storage Temperature: Storing potatoes in temperatures that are either too warm or too cold can induce solanine production. A cool, dark place is ideal to minimize synthesis.
• Physical Damage: Bruises, cuts, and scrapes can trigger the potato's defense mechanisms, causing a localized increase in solanine.
• Age and Aging: As potatoes age, particularly if they begin to sprout, their glycoalkaloid content can rise. Rotting potatoes also contain significantly higher levels and should be discarded immediately.

Can you determine which potatoes are high in solanine by variety?

It is less about the variety and more about the handling and storage of the individual potato. While there are genetic differences, and older or wild varieties may have had higher innate levels (for example, the banned Lenape variety), modern commercial cultivars are bred to have low baseline concentrations. However, any variety can become high in solanine if subjected to the wrong conditions.

Safe Preparation and Storage

To minimize your risk of solanine toxicity, follow these guidelines:

1. Check Before Buying: Inspect potatoes for any greening, sprouting, or damage before purchasing.
2. Store Properly: Keep potatoes in a cool, dark, and well-ventilated place, like a pantry or root cellar, to prevent light exposure and temperature fluctuations.
3. Peel and Trim Thoroughly: Always peel potatoes with any hint of greening. Cut away any green portions, eyes, or damaged areas, going at least an eighth of an inch deeper than the discoloration.
4. Test for Bitterness: A bitter taste is a strong indicator of high solanine levels. If a potato tastes bitter, discard it immediately.
5. Know Your Limits: If a potato is extensively green, soft, or shriveled, it's safest to throw it away entirely.

Comparison of Glycoalkaloid Levels

Potato Condition	Location of Highest Concentration	Average Glycoalkaloid Level (mg/kg)	Risk Level
Normal (healthy, stored properly)	Peel and outer flesh	12–20 mg/kg	Low
Greening (light-exposed)	Underneath the skin and green parts	250–280 mg/kg	High
Sprouting	In the sprouts and surrounding skin	Very high (levels vary)	High
Damaged	Around the injured area	Elevated (localized)	Moderate-High
Wild Potato Species	Throughout the plant	350+ mg/kg (fresh tubers)	Very High

Health Risks of Solanine Toxicity

Consuming high amounts of solanine can lead to acute poisoning. Symptoms often appear 8 to 10 hours after ingestion and can range from mild to severe.

• Gastrointestinal Symptoms: Nausea, vomiting, diarrhea, and abdominal pain are common initial signs.
• Neurological Symptoms: Higher doses can cause more serious effects like headache, dizziness, hallucinations, delirium, and dilated pupils.
• Severe Complications: In very rare and extreme cases, severe poisoning can result in paralysis, shock, and potentially death, though modern cases are uncommon.

Conclusion

While some historical or wild potato varieties contained dangerous levels of solanine, modern commercial potatoes are generally safe when handled correctly. The primary risk comes not from the variety itself but from how a potato is stored and prepared. By recognizing the visual cues of greening and sprouting and practicing proper storage, you can effectively mitigate the risk of solanine poisoning and continue to enjoy potatoes as a nutritious part of your diet. https://www.healthline.com/nutrition/green-potatoes

How Cooking Affects Solanine

• Boiling: Has minimal effect on solanine levels, as the compound is heat-stable and requires very high temperatures to break down. Boiling peeled potatoes may reduce levels slightly through leaching into the water.
• Microwaving: Shows negligible reduction of solanine content.
• Frying: Deep-frying at very high temperatures (above 170°C or 338°F) can significantly reduce solanine, with some studies showing up to a 40% loss.

Overall, no cooking method is a reliable substitute for proper peeling and trimming of green or sprouted potatoes. The best safety practice remains prevention through proper storage and inspection before cooking.

Protecting Your Health

It's estimated that a toxic dose of solanine is about 1 mg per kilogram of body weight. Given the average amount in a green potato, it would take a significant quantity for a healthy adult to experience severe symptoms. Children, however, are more susceptible due to their smaller body weight. If you ever experience symptoms of solanine poisoning, contact a medical professional or poison control immediately.

Frequently Asked Questions

What is solanine?

Solanine is a toxic compound, a glycoalkaloid, that is naturally produced by potatoes and other plants in the nightshade family as a defense mechanism against pests and disease.

Is it safe to eat a green potato after peeling it?

For potatoes with only slight greening, peeling and removing the green parts, along with any sprouts, can significantly reduce the solanine content. However, if a potato is extensively green or tastes bitter, it is best to discard it entirely.

Does cooking destroy solanine in potatoes?

Solanine is heat-stable and not easily destroyed by cooking methods like boiling or microwaving. While deep frying at very high temperatures can reduce it, it is not a reliable method to make a high-solanine potato safe.

What happens if you eat a potato with high solanine?

Consuming high-solanine potatoes can cause gastrointestinal symptoms like nausea, vomiting, and stomach cramps, and in severe cases, neurological issues such as headaches and dizziness.

How should I store potatoes to prevent solanine buildup?

Potatoes should be stored in a cool, dark, and well-ventilated place, like a pantry, cabinet, or cellar, and kept away from light to prevent greening and sprouting.

Can I get solanine poisoning from store-bought potatoes?

Cases of solanine poisoning from commercial potatoes are rare because modern varieties are bred for low levels. The risk comes from improper storage at home, which allows for increased toxin production.

What is the acceptable limit of solanine in potatoes?

The generally accepted safe limit for total glycoalkaloids in potatoes is 20 mg per 100 grams of fresh weight (200 mg/kg), although some countries have different standards.