Green Potatoes: Harmless or Poisonous?

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The greening of potatoes is a natural process.

When exposed to light, potatoes produce chlorophyll, the green pigment that gives many plants and algae their color (1).

This causes light-skinned potatoes to change from yellow or light brown to green. This process also occurs in darker-skinned potatoes, although dark pigments may disguise it.

You can tell whether a dark-colored potato is greening by scratching off part of the skin and checking for any green patches underneath.

Chlorophyll also allows plants to harvest energy from the sun via photosynthesis. Through this process, plants can produce carbs and oxygen from sunlight, water, and carbon dioxide.

The chlorophyll that gives some potatoes their green color is entirely harmless. It’s present in many of the plant foods you eat every day.

Nevertheless, greening in potatoes can also signal the production of a toxic plant compound called solanine (1).

Summary

When potatoes are exposed to light, they produce chlorophyll, a pigment that turns them green. Chlorophyll itself is completely harmless, but it can signal the presence of a toxin.

When exposure to light causes potatoes to produce chlorophyll, it can also encourage the production of certain compounds that protect against damage from insects, bacteria, or fungi (2).

These compounds can be toxic to humans in high doses. However, reports of serious illness are rare.

Glycoalkaloids are the main toxins that potatoes produce. Solanine is a type of glycoalkaloid (3).

Solanine usually is present in low levels in the skin and flesh of potatoes and higher levels in parts of the potato plant. But when potatoes are damaged or exposed to sunlight, they produce more (3).

Greening can indicate higher levels of solanine in a potato, but it isn’t a perfect measure. This is because the green color is caused by chlorophyll, not solanine.

Although the same conditions encourage the production of solanine and chlorophyll, they are produced independently (1).

Under the same conditions, different varieties can produce different amounts of solanine. When a high-solanine potato variety is identified, food safety regulators can remove it from the market (2, 3).

Nevertheless, greening is an indicator that solanine may be present. If you find green spots on a potato, peeling it and trimming away any sprouts (eyes) or green flesh will usually make it safe to eat.

Solanine also causes a bitter flavor. If cooked potatoes taste bitter or cause a burning sensation in your mouth or throat, this can indicate high solanine levels, even if the potato does not look green (2, 4).

Summary

When exposed to light, potatoes produce a toxin called solanine. In very large amounts, solanine can be harmful to humans. Greening in potatoes is a potential indicator of solanine, but peeling and trimming green areas can remove most of the toxin. Solanine also causes a bitter flavor in potatoes.

Many countries have rules to prevent the sale of potatoes containing high levels of solanine and other glycoalkaloids.

The Food and Drug Administration limits glycoalkaloids to 200–250 milligrams (mg) per kilogram (kg) of raw potato, or 91–113 mg per pound (lb). Canada has a similar limit of 200 mg per kg (91 mg per lb), while some European countries have a limit of 100 mg per kg (45 mg per lb) (2).

Even with safeguards in place, potatoes can develop high levels of solanine if they’ve been stored improperly or damaged.

If a potato has developed very high solanine levels, consuming it could make you ill. The risk of illness may be higher for children (2).

Eating large amounts of solanine can cause:

• diarrhea
• vomiting
• abdominal pain
• sweating
• headache

A toxic dose is thought to be 1 mg or more of solanine per kilogram of body weight (0.5 mg per lb), though estimates vary (2).

According to the Missouri Poison Center, solanine exposure is low risk. Even after consuming enough solanine to develop symptoms, most people recover well at home (5, 6).

Extreme cases of solanine poisoning have been reported to cause severe symptoms and even death. However, these cases are incredibly rare (2).

Overall, producers grow and transport potatoes carefully to keep solanine levels low. If you discard the green parts of the potato and do not eat bitter-tasting potatoes, you are unlikely to become ill (4).

Summary

Potatoes that contain very high levels of solanine can cause nausea, vomiting, and abdominal pain. Most cases of solanine exposure resolve without treatment.

Solanine levels are highest in the potato skin (2).

Studies have found that peeling can reduce solanine by 25–75%. You should also remove any sprouts (eyes) and areas of green flesh because they can contain high levels of solanine (2, 4).

The peeled and trimmed potato might still contain enough to make you sick in potatoes with very high solanine concentrations.

However, cooking the potato — such as by boiling, baking, microwaving, or frying it — can further reduce solanine levels (3).

Solanine has a bitter flavor and can cause a burning feeling in your mouth or throat. If a potato tastes bitter after cooking or causes a burning sensation, do not eat it (2, 4).

If a potato has just a few small green spots, you can cut them out or peel the potato. Because solanine is also produced in higher concentrations around a potato’s sprouts (eyes), you should also remove those.

However, if a potato is very green or tastes bitter (an indication of solanine), it’s best to throw it away (7).

Summary

Peeling a green potato and removing any sprouts can significantly reduce its solanine levels. Cooking can also lower the solanine content. It’s best to throw away potatoes if they are very green or have a bitter flavor.

Potatoes that contain unacceptable levels of solanine usually do not make it to the grocery store.

Nevertheless, if not handled properly, potatoes can produce solanine after being delivered to a supermarket or stored in your kitchen.

Proper potato storage can prevent higher levels of solanine.

Physical damage, light exposure, and high or low temperatures are the main factors that stimulate potatoes to produce solanine (2).

Inspect potatoes before purchasing them to ensure they have not been damaged or have already started greening.

Store potatoes in a cool, dark place such as a pantry, cabinet, or drawer. If you have a root cellar or basement, consider storing them there. You can keep them in an opaque sack or paper bag to shield them from light.

The refrigerator is too cold for potato storage. Some studies have even shown increased solanine levels due to storage at refrigerator temperatures (8).

Moreover, the average kitchen or pantry is too warm for long-term storage.

If you don’t have a cool enough place to store potatoes, purchase only the amount you plan to use. Store them in an opaque paper bag in the back of a cabinet or drawer, where they will be best protected from light and warmth.

Summary

Potatoes containing high levels of solanine will usually not make it to the grocery store. Storing them in a paper bag in a cool, dark place such as a drawer or cupboard may prevent them from turning green after purchase.

The following includes frequently asked questions about green potatoes.

Can you eat potatoes with a green tinge?

You can likely eat potatoes with a green tinge if you remove the green parts and the skin. But if the potato tastes bitter or makes your mouth burn, it may contain high toxin levels. In that case, it may be best to discard it.

What does it mean when potatoes turn green?

Potatoes turn green when they are exposed to sunlight or damaged. The green pigment comes from chlorophyll. Sunlight can also cause potatoes to produce the toxin solanine.

Is it OK to eat green Yukon Gold potatoes?

It may be safe to eat green potatoes if you peel them, remove green parts, and cook them. But you may want to avoid eating them if they taste bitter or make your mouth burn. This may mean high levels of the toxin solanine.

Does boiling potatoes remove solanine?

Cooking potatoes through boiling or another method may reduce the amount of solanine they contain. You can also remove solanine by peeling the potato and cutting away any green spots.

Green potatoes should be prepared carefully.

Although the green color itself is not harmful, it may indicate the presence of a toxin called solanine.

Peeling and trimming green potatoes can help reduce solanine levels. If a potato is green throughout or your potato dish tastes bitter, it’s best to throw it away.

Inspect potatoes for greening and damage before buying them, and store them in a cool, dark place to prevent them from going green before you use them.