What part of the potato is toxic?

January 11, 2026 •

4 min read

According to research, potatoes naturally produce toxic compounds called glycoalkaloids, primarily solanine, which can increase significantly under specific conditions. While a staple food, certain parts of the potato, especially when poorly stored, can become hazardous if consumed in large quantities, making vigilance crucial for home cooks.

Quick Summary

The most toxic parts of a potato are the green areas, sprouts, and leaves, containing elevated levels of solanine. This natural toxin, a glycoalkaloid, develops when the potato is exposed to light or physical damage and should be removed before eating.

Key Points

Toxin is Solanine: The primary toxic compound in potatoes is a glycoalkaloid called solanine, a natural defense mechanism.
Toxic Parts to Avoid: Solanine is most concentrated in the potato's green skin, sprouts, and leaves.
Visual Warning: Green discoloration is a harmless pigment (chlorophyll), but it signals the concurrent, and dangerous, increase of solanine.
Taste Test Indicator: A bitter taste in a raw or cooked potato is a reliable sign of high solanine levels and indicates it should be discarded.
Proper Storage is Key: Storing potatoes in a cool, dark, and dry place prevents greening and sprouting, thus minimizing toxin buildup.
Peeling is a Solution: For slightly greened potatoes or those with small sprouts, peeling them deeply and removing all affected parts can render them safe.
Cooking is NOT Enough: Cooking methods like boiling or baking do not effectively destroy solanine, making physical removal of toxic parts essential.

The Toxic Compound: A Potato's Natural Defense

The toxicity in potatoes is due to naturally occurring compounds called glycoalkaloids, with the most notable being solanine and chaconine. These bitter-tasting neurotoxins are the plant's defense mechanism against pests, fungi, and other environmental stressors. While present in low, generally harmless amounts in properly grown and stored potatoes, their concentration can spike dramatically under certain conditions.

Where Glycoalkaloids Concentrate

The highest concentrations of these toxins are not found throughout the entire edible tuber but rather accumulate in specific areas, particularly when the potato is stressed. The concentration of solanine is highest in:

The Green Skin and Flesh: When a potato is exposed to light, it produces chlorophyll, causing the skin to turn green. This green color is a visual indicator that the same conditions have triggered a significant increase in solanine production.
The Sprouts (Eyes): The sprouting 'eyes' of a potato are areas of new growth where the plant concentrates its defenses. As sprouts develop, they contain very high levels of solanine.
The Leaves and Stems: While we typically only eat the potato tuber, it's important to remember that the potato plant itself is a member of the nightshade family, and its aerial parts (leaves and stems) are toxic and should never be consumed.

Identifying and Handling Unsafe Potatoes

Detecting high levels of solanine isn't difficult once you know the signs. The most reliable indicators are visual cues and taste.

Visual Check: The most obvious sign is the greening of the skin or flesh, caused by chlorophyll, which signals high solanine. Bruising or physical damage can also indicate elevated toxin levels.
Taste Test: If a potato or potato dish tastes bitter, it's a strong indication of high solanine levels. Even if it's not green, a bitter flavor warrants discarding it.

What to Do with Compromised Potatoes

When a potato shows signs of increased solanine, your action depends on the severity:

Slight Greening or Small Sprouts: Peel the potato generously, removing all green-tinged areas and sprouts. The solanine is typically concentrated near the surface, so a deep peel is effective.
Extensive Greening or Large Sprouts: If the potato is significantly green throughout or has large, soft sprouts, discard it entirely. There is too much risk that the toxin has permeated the flesh.
Bitter Taste: If a cooked potato tastes bitter, stop eating it immediately and throw the rest away, regardless of its appearance.

Safe Storage is Key

Proper storage is the best preventative measure against solanine buildup. Factors like light, temperature, and physical damage trigger the potato's defense mechanisms. To ensure safety:

Store potatoes in a cool, dark, and dry place, such as a pantry or cellar, to prevent light exposure.
Keep them away from direct sunlight and artificial fluorescent lights.
Store them in a breathable bag or basket, not a sealed container, to allow for air circulation.
Avoid storing potatoes with onions, as gases from onions can accelerate sprouting.

Safe vs. Unsafe Potato Parts


Feature	Potentially Safe Part	Potentially Unsafe Part
Appearance	Uniform, clean skin color (tan, red, etc.) and firm texture.	Green skin or green flesh just beneath the peel. Shriveled or soft texture.
Growth	No visible sprouts or only tiny buds.	Extensive, long sprouts ('eyes').
Flavor	Starchy, mild, classic potato flavor.	Distinctly bitter, causes a burning sensation in the mouth.
Toxin Levels	Low, standard glycoalkaloid levels.	Elevated, potentially dangerous solanine levels.
Handling	Wash, peel if desired, and cook.	Discard if heavily compromised or tastes bitter. For slight greening/small sprouts, peel and remove affected areas.

A Note on Solanine Poisoning

Most cases of potato-related solanine poisoning are mild, causing temporary gastrointestinal distress such as nausea, vomiting, or diarrhea. Severe poisoning is extremely rare but can lead to more serious neurological issues. The natural bitter taste of high-solanine potatoes acts as a strong deterrent, making it unlikely that a person would consume a toxic dose. However, it is always wise to err on the side of caution. For more information on poisoning prevention, you can visit a reliable source such as the Poison Control website.

Conclusion: Minimizing the Risk

While potatoes are a healthy and delicious part of our diet, they require mindful handling to ensure safety. The key takeaway is simple: the green skin and developing sprouts are the toxic parts to avoid. By storing potatoes correctly in a cool, dark place and taking a moment to inspect and prepare them properly, you can easily minimize the risk of solanine exposure. When in doubt, trust your senses—if it looks very green or tastes bitter, the safest option is to throw it out and start fresh. Your health is worth more than saving a potentially compromised potato.

Frequently Asked Questions

Not all green potatoes are toxic, but the green color is a warning sign that the potato has been exposed to light, which increases the production of the toxin solanine. It is always safest to peel away any green parts.

Yes, if a potato is firm and the sprouts are small, you can cut off the sprouts deeply before cooking. However, if the potato is wrinkled, soft, or has large sprouts, it should be discarded.

Consuming a potato with high levels of solanine can cause symptoms like nausea, vomiting, abdominal pain, and diarrhea. Severe poisoning is rare but possible with large quantities.

Cooking methods like boiling and baking do not destroy solanine effectively. It is essential to physically remove the toxic, green parts before cooking to ensure safety.

In most cases, yes. A deep peel that removes all green areas, plus any sprouts, can remove the majority of the solanine. However, if the greening is extensive or the potato tastes bitter, it should be discarded.

Potatoes turn green when exposed to light, a process that triggers the production of chlorophyll. This light exposure also stimulates the production of solanine, the toxic compound.

To prevent greening, store potatoes in a cool, dark, and dry place. A pantry, cellar, or cupboard in a breathable paper bag is ideal to keep light away.