What is the toxin in sweet potatoes?

October 12, 2025 •

4 min read

Over decades of research, scientists have identified a class of toxic compounds called furanoterpenoids, primarily ipomeamarone, which are the culprits behind sweet potato poisoning. These toxins are not present in fresh, healthy sweet potatoes but are produced by the plant in response to stress, most notably fungal infections.

Quick Summary

The toxin in sweet potatoes is ipomeamarone, a furanoterpenoid produced in response to fungal infection, not present in healthy tubers. Other toxic compounds, like 4-ipomeanol, are also produced under stress. It is crucial to identify and discard mold-damaged or otherwise compromised potatoes to prevent toxicity.

Key Points

Ipomeamarone is the primary toxin: This compound, a furanoterpenoid, is produced by sweet potatoes only when they are stressed, infected with fungus (Fusarium solani), or physically damaged.
Toxins are not always visible: While visible mold is a key sign, toxins can accumulate in seemingly healthy portions of an infected tuber, making the entire sweet potato unsafe.
Risks for animals and humans: Historically linked to livestock deaths from pulmonary edema, human consumption of moldy sweet potatoes can cause food poisoning, liver damage (hepatotoxicity), and other symptoms.
Look for warning signs: Reject sweet potatoes that are soft, mushy, discolored with black or dark spots, moldy, or have a foul, musty smell.
Prevention through proper storage: Store sweet potatoes in a cool, dark, and dry place to prevent mold growth and stress-induced toxin production.
Cooked toxins are still dangerous: Cooking does not eliminate all toxins, so the best practice is to discard any sweet potato showing signs of spoilage.
The difference from regular potatoes: Sweet potatoes do not produce solanine, the toxin found in green or sprouting regular potatoes.

The Toxic Culprit: Ipomeamarone and Other Furanoterpenoids

Unlike standard potatoes, which contain the glycoalkaloid solanine when green or spoiled, the toxin in sweet potatoes is a completely different class of compounds called furanoterpenoids. These compounds are not a natural part of a healthy, fresh sweet potato but are produced as a defense mechanism when the tuber is stressed. The most well-known of these is ipomeamarone, but other related compounds like 4-ipomeanol and ipomeanine are also part of this toxic mix. The production of these toxins is a direct response to damage caused by insects, fungi, or physical injury.

The Trigger: Fungal Infection and Stress

The primary trigger for the production of these toxic furanoterpenoids is an infection by a fungus, most commonly Fusarium solani, which causes black rot. However, other pathogens and even chemical damage can also initiate this defense response. When the fungus attacks, the plant produces these compounds, which are concentrated in the necrotic (damaged) tissue but can also accumulate in surrounding, seemingly healthy tissue. This is a critical point for food safety, as the entire sweet potato, not just the visibly damaged part, can contain dangerous levels of the toxins.

Toxicity in Animals and Humans

Incidents of sweet potato toxicity have historically been more documented in livestock, particularly cattle, that have been fed moldy or damaged sweet potatoes. In these animals, the toxins can cause severe pulmonary edema, emphysema, and liver damage, leading to death. The danger to humans, while less common, is still a significant concern. The toxin 4-ipomeanol has been found to cause specific pulmonary damage in laboratory animals and is believed to be the cause of interstitial pneumonia in cattle. While human livers can metabolize 4-ipomeanol, this process can produce reactive intermediates that are still hepatotoxic, posing a risk of liver damage. Therefore, consuming moldy sweet potatoes can lead to food poisoning with symptoms including vomiting, nausea, and abdominal cramps.

Comparison of Sweet Potato vs. Regular Potato Toxins


Characteristic	Sweet Potato (Ipomoea batatas)	Regular Potato (Solanum tuberosum)
Primary Toxin(s)	Ipomeamarone, 4-ipomeanol, ipomeanine (furanoterpenoids)	Solanine and chaconine (glycoalkaloids)
Toxin Source	Produced as a stress response to fungal infection, insect damage, or physical injury	Naturally present in small amounts, but increases when exposed to sunlight (turns green) or when sprouting
Toxic Conditions	Moldy, soft, or visibly rotting tubers. The toxin can spread to seemingly healthy sections.	Green-skinned potatoes, sprouts, and eyes.
Key Visual Cue	Soft spots, dark/black discoloration, mold, bad smell.	Green skin, sprouts, and eyes on the tuber.
Primary Organ Affected	Lungs (in animals), liver (in humans and animals).	Gastrointestinal and neurological systems.

Identifying and Avoiding Toxic Sweet Potatoes

To ensure safety, it's vital to inspect sweet potatoes before purchasing and again before cooking. A healthy sweet potato should be firm and have smooth, unblemished skin. Here is a checklist for identifying a potentially toxic sweet potato:

Visible Mold or Discoloration: Any fuzzy white, black, or green mold or dark, discolored patches on the skin are major red flags.
Soft or Mushy Spots: A healthy sweet potato is firm to the touch. Any soft or squishy areas indicate rotting and potential toxin presence.
Unpleasant Smell: Trust your nose. A sour, musty, or rotten smell is a clear sign of spoilage and should not be ignored.
Oozing Liquid: If a sweet potato is oozing a strange, mysterious liquid, it has likely gone bad.
Extensive Damage: While small blemishes can sometimes be cut away, extensive black spots or deep wrinkles are often indicative of a widespread problem within the tuber. When in doubt, it's always safer to discard the entire potato.

Safe Handling and Storage

Proper storage can prevent the conditions that lead to toxin production. Sweet potatoes should be stored in a cool, dark, and dry place, with good ventilation. Avoid refrigerating raw sweet potatoes, as this can affect their taste and texture. By preventing mold and spoilage, you eliminate the risk of ipomeamarone formation. If you do find a sweet potato with a small, localized dark spot, you can cut away the affected portion, but if there is any doubt about the extent of the damage, it is best to dispose of the entire tuber. This is especially important for individuals who might be more sensitive or have compromised immune systems.

Conclusion

While fresh, healthy sweet potatoes are a nutritious and safe part of the human diet, they can become toxic when damaged or infected with mold. The primary toxin in sweet potatoes is ipomeamarone, a furanoterpenoid produced as a stress response to fungal attacks. Unlike regular potatoes, which develop solanine, this toxin poses different risks, including potential liver and lung damage, though documented human cases are rare. To ensure safety, always inspect your sweet potatoes for signs of spoilage such as mold, soft spots, and a foul odor. By storing them properly and exercising caution, you can enjoy this versatile vegetable without worry. The most important rule to remember is: when in doubt, throw it out.

Frequently Asked Questions

No, it is not safe to eat a sweet potato with mold on it. Moldy sweet potatoes can contain toxic compounds like ipomeamarone and 4-ipomeanol, which can lead to food poisoning and more severe health issues.

The toxins are different. Regular potatoes produce glycoalkaloids like solanine when they turn green or sprout. Sweet potatoes produce furanoterpenoids, such as ipomeamarone, in response to fungal infection.

Cooking does not reliably destroy the toxins in moldy sweet potatoes. Studies have shown that while some steam-distillable compounds may be reduced, cooking the intact sweet potato does not eliminate all the toxins. It is safest to discard the entire potato.

Symptoms of consuming a bad sweet potato can include nausea, vomiting, abdominal pain, diarrhea, and cramps. In severe cases, it can cause liver or lung damage.

Look for sweet potatoes that are firm, with smooth, unblemished skin. Avoid any that have soft spots, mold, black or dark discoloration, or an unpleasant smell.

No, you should not eat any part of a moldy sweet potato. The toxins can spread throughout the potato, even to parts that appear healthy and free of mold. When in doubt, it is best to throw it out.

While human cases are less common than in livestock, ipomeamarone and related furanoterpenoids, like 4-ipomeanol, can be toxic to humans, potentially causing hepatotoxicity (liver damage).

Store sweet potatoes in a cool, dark, and well-ventilated area, away from direct sunlight. Do not store them in the refrigerator before cooking, as the cold can change their texture. Proper storage prevents mold growth, thus preventing toxin production.