Everything You Need to Know About Reheated Rice Syndrome

Once again, TikTokers are freaking out that there's a hidden scourge in the kitchen: day-old rice. Fittingly for a controversy about leftovers, many claims are nearly a year old — but that isn't stopping people from resurfacing horror stories, claiming they got food poisoning from reheating rice that was left sitting out overnight.

"Being a med student means never being able to comfortably reheat rice ever again," second-year medical student Janny Garcia wrote in a viral TikTok post with more than a thousand comments. Another user — with a Ph.D. in microbiology — took to the platform to explain reheated rice syndrome, as the ailment is often referred to, saying: "Most things that are going to cause human disease have an optimal growing temperature between about 20°C [68°F] and 30°C [86°F] … so that means don't ever let your food that needs to be cooked sit out at room temperature. You don't want it to be at that level of temperature for any length of time."

But what's the truth?

Like many foods, uncooked rice contains a foodborne pathogen known as Bacillus cereus — or B. cereus — and these incredibly heat-resistant spores can survive even when rice is cooked. According to the USDA, the microorganism grows best between 39°F and 118°F but cannot germinate in the cold (or invade acidic foods). Beyond that, increased salinity helps it thrive.  

When rice is left unrefrigerated, the spores can develop into bacteria that may cause stomach issues such as vomiting or diarrhea. The symptoms, while unpleasant, typically last no longer than 24 hours. But know that consuming B. cereus in low levels is not harmful. 

However, rice that has been properly refrigerated can keep about four to six days, according to the U.S. Department of Health and Human Services. And it shouldn’t be reheated more than once. In fact, reheating properly cooled rice could even be beneficial (especially for Type 2 diabetics and those with bowel diseases like Crohn’s or ulcerative colitis) because it’s considered a resistant starch.

Unlike traditional carbs, resistant starches function more like soluble, fermentable fiber — bypassing the stomach and small intestine undigested. This has several benefits: First, it “feeds” the good bacteria in your gut, allowing for a lower pH level and reducing inflammation. It also improves insulin sensitivity by diluting the digestible starches in any given meal, reducing insulin response and lowering the glycemic load. 

For now, the reheated rice panic is still simmering, but understanding how to properly store such an important food staple should help rice lovers chill out.