What is the toxin in potato peels? Understanding glycoalkaloids

December 15, 2025 •

3 min read

When exposed to light or physical damage, potatoes naturally produce a toxic compound called solanine as a defense mechanism. This toxin, along with a related compound known as chaconine, are both types of glycoalkaloids found in potato peels. Higher concentrations are present in the green parts, sprouts, and eyes of the potato, so proper storage is key to preventing them from becoming a health risk.

Quick Summary

Potato peels contain natural toxins called glycoalkaloids, primarily solanine and chaconine, which serve as the plant's defense mechanism. Their concentration increases with light exposure, damage, and sprouting, often indicated by a green color. Removing the skin and green parts, and discarding any bitter-tasting potatoes, is the safest approach to prevent illness.

Key Points

Identify the toxin: The primary toxins in potato peels are glycoalkaloids, specifically α-solanine and α-chaconine.
Know the trigger: Exposure to light, physical damage, and sprouting trigger an increase in these toxic compounds.
Recognize the warning sign: The harmless green color of potatoes is a reliable indicator that glycoalkaloid levels may also be high.
Taste test for bitterness: A bitter flavor is the most reliable sign of a high concentration of toxins; if a potato tastes bitter, discard it.
Store properly: Keep potatoes in a cool, dark, and dry place, away from light and other produce like onions, to minimize toxin production.
Peel and trim for safety: If a potato has only minor greening or eyes, peel it thickly and remove those areas to reduce toxin levels significantly.
Avoid extensive greening: Throw away potatoes that are extensively green or taste bitter, as cooking does not destroy the toxin effectively.

The Chemical Culprits: Solanine and Chaconine

The toxins found in potato peels are a class of compounds known as glycoalkaloids. The two most significant and commonly discussed types are α-solanine and α-chaconine. These compounds are naturally present in all parts of the potato plant, but are most concentrated in the leaves, flowers, and the parts of the tuber that are exposed to light. Their production is a natural defense mechanism for the plant, helping to deter pests, bacteria, and fungi.

Potatoes stored in conditions that expose them to light, damage, or extreme temperatures will synthesize more of these glycoalkaloids. The characteristic green color that appears on some potatoes is caused by chlorophyll, which is harmless, but it serves as a reliable visual indicator that the potato has been exposed to light and may contain higher levels of the toxic glycoalkaloids. The toxins themselves are colorless and produce a distinct bitter taste.

The Health Risks Associated with Glycoalkaloids

While low levels of glycoalkaloids are generally harmless, ingesting large amounts can cause illness, leading to a condition known as solanine poisoning. Symptoms typically include gastrointestinal and neurological issues. The severity depends on the concentration of the toxin and the amount consumed. Fortunately, severe poisoning is rare due to the bitter taste, which usually prevents people from eating highly toxic potatoes.

Common symptoms of glycoalkaloid poisoning include:

Nausea
Vomiting
Diarrhea
Stomach cramps
Headaches
Dizziness
Fever

In very rare and severe cases, symptoms can escalate to hallucinations, paralysis, and in extreme circumstances, can be fatal, although this is incredibly uncommon.

Proper Handling and Storage to Mitigate Risk

To minimize the risk of glycoalkaloid buildup, proper handling and storage of potatoes is crucial. The most effective strategy is prevention, but if you do find a green or sprouting potato, there are steps you can take to make it safer.

What to do with green or sprouting potatoes

Small green spots or eyes: For a minor green tinge or small sprouts, simply peel the potato thickly, removing the skin and at least an eighth of an inch of the flesh beneath it. Also, cut out any sprouts or eyes completely. The remaining inner flesh is typically safe to eat, provided it does not have a bitter taste.
Extensive greening or bitterness: If the potato is very green throughout or has a noticeable bitter taste after cooking, it is best to discard it entirely. Cooking does not effectively destroy these heat-stable compounds, so relying on heat to eliminate the toxin is unsafe.

Best practices for storage:

Store in a cool, dark place: Light exposure is the primary trigger for glycoalkaloid production. Keep potatoes in a dark, cool area like a pantry, cabinet, or cellar.
Use an opaque container: Storing potatoes in a paper bag or opaque sack protects them from light. Avoid storing them in plastic bags, which can trap moisture and accelerate spoilage.
Keep away from other produce: Do not store potatoes near onions, as the gases they emit can speed up sprouting in potatoes.

Comparison of Toxin Locations in Potatoes

It's useful to understand where these toxic compounds are concentrated to make informed decisions about preparing your potatoes. The distribution of glycoalkaloids is not uniform throughout the tuber.


Feature	Toxin Level	Proper Handling
Skin	High	Peel away the skin, especially if green.
Eyes/Sprouts	Very High	Remove and discard all sprouts and eyes.
Green Flesh	High	Cut away all green parts completely.
Inner Flesh	Low (if not green or bitter)	Typically safe to eat after green parts and skin are removed.
Bitterness	High, regardless of color	Discard the entire potato if it tastes bitter.

Conclusion

The presence of glycoalkaloids, like solanine and chaconine, in potato peels is a natural defense mechanism that can pose a health risk if improperly handled. The key takeaway is to prevent the buildup of these toxins by storing potatoes in a cool, dark place and away from light. While peeling and cutting away minor green areas is effective for potatoes with minimal discoloration, extensive greening or any bitter taste warrants immediate disposal of the entire potato. By following these simple kitchen safety measures, you can continue to safely enjoy potatoes as part of a healthy diet.

Frequently Asked Questions

No, potato peels are not always toxic. Fresh, properly stored potatoes have low, safe levels of glycoalkaloids. Toxicity is a concern only when the potatoes are green, sprouting, or have been damaged.

Solanine poisoning is an illness caused by consuming large amounts of glycoalkaloids, such as solanine. Symptoms include vomiting, diarrhea, abdominal pain, and headaches. Severe cases are very rare but can be serious.

No, cooking does not effectively remove or destroy the glycoalkaloid toxins in potatoes. These compounds are heat-stable, meaning they can withstand boiling, baking, and frying.

The green color is caused by chlorophyll, which is harmless. However, it indicates that the potato has been exposed to light, a condition that also stimulates the production of the toxic glycoalkaloids.

For potatoes with minor green spots or a slight green tinge, you should peel the skin thickly and cut away all green parts. If the potato is extensively green or has a bitter taste, it is safest to discard it.

Glycoalkaloids are most concentrated in the potato's peel, the flesh directly under the skin, and the sprouts or 'eyes.' The lowest concentration is found in the inner, white flesh.

To prevent glycoalkaloid buildup, store potatoes in a cool, dark, and dry place. Keep them in a paper bag or other opaque container to block light and away from other produce like onions.