In Too Afraid to Ask, we’re answering the food-related questions you may or may not be avoiding. Today: Can you actually get food poisoning from leftover rice?
People all over TikTok are claiming that eating leftover rice made them sick. In one clip, a woman in a patterned hospital gown is hunched over in bed like an apostrophe. While horizontal in a dark room, another user whispers into the camera, “Rice poisoning is the worst type of food poisoning I have ever gotten in my entire life.” Yet another, who supposedly just ate a bowl of rice that had been out of the fridge all night, writes: “I DONT WANNA GET DIHARREA,” followed by two sobbing emojis.
What’s the deal? According to experts, toxins produced by a microorganism called Bacillus cereus, are the culprit. If grain-based foods like rice—but also pasta, quinoa, and more—are stored incorrectly after cooking, Bacillus cereus can multiply and cause stomach issues such as vomiting and diarrhea. Though rice poisoning is having a moment on social media right now, fervor around this foodborne illness has been waxing and waning well before TikTok, says Donald Schaffner, PhD, a food science professor at Rutgers University.
That’s partially thanks to a small number of severe cases, which continue to circulate online. In 2003, five siblings from Belgium became ill after eating pasta salad that had been made for a picnic and served again for dinner three days later. The youngest, a seven-year-old girl, died in the hospital after her liver failed. Five years later, a 20-year-old student from Belgium also died after eating five-day-old spaghetti, which he’d made and left out in the kitchen at room temperature. In both cases, Bacillus cereus toxins were identified as the cause of death.
This type of foodborne illness is fairly common: In the US, there are an estimated 63,400 instances of Bacillus cereus–caused cases each year. Typically, they’re mild. “Victims experience vomiting or diarrhea and feel generally terrible, but most go on to make a full recovery,” says Schaffner. “In some cases, though, if a large amount of toxin is ingested, it can cause death.” So, what exactly is Bacillus cereus? Why does it form toxins in foods like rice? And how can you avoid that happening? Here’s what to know.
How does rice food poisoning occur?
Bacillus cereus is all around us: It’s in soil, fresh and marine waters, on plants, and even inside the gut of some animals. That means foods like rice, which are grown in environments where the microorganism is abundant, can easily carry it with them.
At low levels, Bacillus cereus likely won’t make you sick. “We all probably eat the spores or cells on a regular basis with no adverse effects,” says Schaffner. But when the bacteria multiplies in food, two kinds of toxins are formed as a by-product. Schaffner explains: “You can think of them as toxic poop excreted by the organism.” At high enough concentrations, these can make people sick, says Rosemary Trout, DHSc, a food science professor at Drexel University. One causes diarrhea and the other vomiting—that latter of which is more commonly associated with cooked rice.
Temperature plays a key role in Bacillus cereus growth. The organism forms heat-resistant spores that can persist for long periods of time and don’t die when rice or other grains are boiled. When cooked grains cool and enter the “danger zone,” a term microbiologists use to describe a temperature range between 40°F–140°F, those Bacillus cereus spores begin to germinate. Chances are your house, and maybe even the keep-warm setting on your rice cooker, falls somewhere on this spectrum. So, if rice isn’t cooled and refrigerated as soon as possible after cooking, Bacillus cereus can proliferate and release toxins into your food.
Can it happen with other foods too?
Sickness from improperly cooled and stored rice is so common globally that it’s sometimes referred to as fried rice syndrome. But this term is culturally problematic and technically misleading: Bacillus cereus poisoning “is not just a rice specific phenomenon,” says Schaffner. The bacteria can be found in all cereal products, such as pasta (the culprit behind the two deadly cases in Belgium), noodles, couscous, farro, and more.
That said, rice might be more likely to cause sickness than grains like wheat, mostly due to the nature of how it’s processed. “Rice grows directly in soil without [much more] transformation before cooking and consumption,” says Trout. Whereas pasta is more processed and “further removed from the soil and even the wheat from which it’s made.” Meaning, rice might be more likely to contain a higher concentration of Bacillus cereus than other grains—and more at risk of proliferating to higher levels in the danger zone.
Does reheating contaminated food prevent sickness?
Reheating leftover rice to temperatures higher than the upper limit of the danger zone—Trout recommends aiming for 165oF in the microwave—can help prevent any toxins that might have formed from multiplying. But once they’re in your food, “no amount of reheating can make it safe again,” says Schaffner. Following proper cooling and storage recommendations is the best way to minimize your risk of bacteria multiplying and making you sick.
So, how should you handle leftovers?
Once rice or other grains are fully cooked, you’ll want them to spend as little time as possible in the danger zone to avoid Bacillus cereus growing in your food, says Trout. “You can spread cooked grains out on a sheet tray so that surface area is maximally exposed and heat dissipates more quickly.” Then, store leftovers in an airtight container in a fridge that’s colder than 40oF.
Alternatively, Schaffer suggests transferring cooked rice, pasta, etc., to a shallow container and placing it, uncovered, in the fridge until it cools down. Once the food is as cold as your fridge, you can put the lid on.
How long does leftover rice last?
Cooked rice that’s been stored properly in the fridge should be eaten within four to six days, according to the USDA. Trout personally won’t let her leftovers linger longer than a few days. “With opening and closing of home refrigerators all day, it’s possible that the rice will be above 40oF at least part of the time,” she says, which could allow Bacillus cereus to grow and produce toxins, albeit slowly.
Your cheat sheet: Cook grains to temperatures above 140oF, immediately cool and store them in a fridge that’s colder than 40oF, and chuck the leftovers after a few days.