What you see: Greenish skin on a potato.
What it is: Chlorophyll buildup that signals higher levels of specific types of glycoalkaloids, which can be harmful if you consume them at high concentrations.
Eat or toss? Is it just a little green? If so, cut or peel away the green area, and eat! But if your potato is starting to look like an emerald, and especially if it’s also sprouting and softening, it’s time to toss.
So, are green potatoes edible?
A potato with green skin can still edible. However, it’s a sign the potato may have produced elevated levels of glycoalkaloids, which can cause illness if you ingest too much of them. The greener (and more sprouted and more wrinkly) a potato is, the more likely it is to have higher levels of the compounds. Glycoalkaloids concentrate in the peel and sprouts, though they can eventually spread throughout the tuber.
All that said, documented cases of people getting sick from eating green potatoes are extremely rare. Roy Navarre, a research geneticist at the U.S. Department of Agriculture who specializes in potatoes, said he’s comfortable peeling away green areas, but draws the line at softening and advanced sprouts.
“I personally have never come across a potato from the grocery store or farmers market where peeling didn’t take care of the issue,” he said. “But if it was soft or had sprouts I’d probably discard it because it’s not going to taste good anyway.”
Nora Olsen, a potato specialist at the University of Idaho, said that if a potato is slightly green in one area, she’ll just cut that part off. If it’s a deep, vivid green, or green all over, however, she’ll toss it. In large part, she said, because it probably won’t taste good at that point.
Ultimately, while a green, shriveling, sprouting potato is a hard no, it’s virtually impossible to specify a degree of greening on an otherwise normal-looking potato that could be problematic. Especially as illnesses are rare, it comes down to your personal tolerance for a slight risk.
Why potatoes turn green
The “green” in green potatoes is harmless chlorophyll, which the potato happily created when it was exposed to natural or artificial light.
It’s the kind of thing that might happen in the farmer’s field if there was a crack in the soil, in the grocery store under those bright fluorescent lights, or even in your kitchen if you’ve left them on the counter uncovered. (Rule: keep your potatoes in the dark as much as possible.)
A defensive chemical lurks in green potatoes
The chlorophyll won’t hurt you, but it does indicate that glycoalkaloids are likely also boosting their concentrations, especially in the peel. Those glycoalkaloids don’t need light to develop, but they form faster and in greater volumes in a bright environment.
Glycoalkaloids also accumulate in those sprouting potato “eyes” and can cause some nasty things, including severe gastrointestinal distress, along with vomiting and diarrhea, and even death (again, this is extremely rare). Potato glycoalkaloids affect the nervous system and can mess with the body’s ability to regulate a chemical involved in nerve impulses.
But a small amount of potato glycoalkaloids won’t make you sick. In fact, any time you’re eating potatoes you ingest small amounts of them—they even contribute to the potato’s taste. Potatoes use glycoalkaloids to ward off microbial and insect pests. Researchers are even studying their potential to treat cancer in people. Like many substances, it’s the dose that makes the poison and potatoes that are greening can carry a larger dose.
You need to eat a lot of glycoalkaloids to get sick
While glycoalkaloids are present in trace amounts in normal-looking potatoes, a 200-pound person would need to eat 20 pounds of not-green potatoes in a single day to reach toxic levels, according a report published by the University of Nebraska – Lincoln Extension.
If, writes author Alexander Pavlista, those potatoes had been exposed to light—which can easily increase glycoalkaloid concentrations by a factor of 10—that same person could suffer to some degree after eating two pounds of potatoes. For perspective, a large baked potato can weigh about a pound.
Reports of people sickened by green potatoes are rare. Though it’s also possible that people who only suffer mild symptoms never connect their illness to having eaten green potatoes.
You’ll probably taste bitterness in a green potato before it harms you
Here’s a bit of good news—high concentrations of glycoalkaloids taste so bad that you may notice the bitter flavor before you’ve consumed enough to make you sick. While most of us don’t eat our potatoes raw, a 1970 paper in the American Potato Journal said eating raw potatoes with elevated glycoalkaloids created a “burning sensation at the sides and the back of the oral cavity, not unlike the taste of hot peppers.”
Olsen has studied glycoalkaloid concentration in potatoes, but when she encounters a potato with a bit of green in her kitchen, her first worry is flavor, not sickening people.
“They’d have to be really green to get at levels that are going to cause you issues,” she said.
Worth keeping in mind—glycoalkaloids tend to concentrate in the peel, so that’s an area where you should be cautious. Also important: while cooked potatoes will stop producing glycoalkaloids, and while cooking might lower levels a bit, cooking won’t elimate them.
Potatoes sold in the US are typically low in glycoalkaloids
One more bit of good news: When it comes to glycoalkaloids, Olsen says that the potato industry has your back. The potatoes that are bred and distributed are selected for their tendency to produce low amounts of glycoalkaloids.
“There’s work in the background going on,” she said.
For more on green potatoes, including what happens when red potatoes turn “green” and a taste test I conducted on a partially green potato, check out the post, “Red potato with dark patches and green under the peel.”
SOURCES:
- Roy Navarre. Research Geneticist. United States Department of Agriculture.
- Nora Olsen – Potato Specialist for the University of Idaho
- A Review of Important Facts about Potato Glycoalkaloids by Marita Cantwell. Perishables Handling Newsletter.
- G1437 Green Potatoes: The Problem and the Solution. Alexander D. Pavlista. University of Nebraska at Lincoln. Jan. 1, 2001.
- Idaho Potato Commission. FAQ
- Tater Taught: Are Green Potatoes Poisonous? Snopes.com
- Healthy Foods that Can Kill You. Cooking Light.
- Horrific Tales of Potatoes that Caused Mass Sickness and Even Death. Smithsonian.com
- FDA Poisonous Plant Database (Now decommissioned)
- Updated aspects of alpha-Solanine as a potential anticancer agent: Mechanistic insights and future directions. Sudeshna Nandi, Rimpa Sikder, Anish Nag, Somanjana Khatua, Surjit Sen, Nilanjan Chakraborty, Arghya Naskar, Kairat Zhakipbekov, Krishnendu Acharya, Solomon Habtemariam, Dilek Arslan Ateşşahin, Tamar Goloshvili, Afaf Ahmed Aldahish, Javad Sharifi-Rad, Daniela Calina. Food Science & Nutrition. August 29, 2024. Accessed September 2024.
Updated September 2024