Is it safe to eat leftover rice? Here's the truth, according to nutritionists.

Of the many things that white or brown rice is known for, being filling is high on the list. Whether it's a side dish at a favorite Japanese restaurant, fried rice takeout from a Chinese fast-food chain, or a plate of chicken and rice cooked up at home, more often than not we tend to have more rice on our plates than we can finish in one sitting.

For many of us, these leftovers are a welcome snack to refrigerate and get into later. But sometimes reheating leftover rice comes with unique health risks. It can be helpful to understand which circumstances are (and aren't) OK to indulge in eating rice leftovers.

Is it safe to eat leftover rice?

The first thing to understand is that it is OK to eat leftover rice, so long as it has been refrigerated and stored properly, and in a timely manner after preparation. "When eating any leftovers, it is important to follow the right practices to avoid foodborne illnesses," says Jen Messer, a nutrition consultant and registered dietitian at Jen Messer Nutrition. She explains that trained dietitians like herself follow the acronym FATTOM, which stands for Food, Acidity, Temperature, Time, Oxygen and Moisture. Each word refers to various aspects of any leftovers that one can look out for such as the type of food one is reheating, the acidity of each item in question, the temperature at which the food needs to be prepared and stored, the time it takes for different foods to develop microbial growth, the presence of oxygen that some microorganisms need to thrive, and whether moisture is present that could increase risk of contamination.

All of this applies to heating leftover rice because certain foods provide a more conducive environment for bacterial growth than others. "Cooked rice is particularly susceptible to bacterial growth due to its moist environment, especially if it is left at room temperature for an extended period of time," says Messer. Moisture often leads to mold and other forms of bacterial growth.

Spoilage also occurs because uncooked rice often contains spores of bacteria that can survive cooking. These are known as Bacillus cereus and they can multiply under the right circumstances. "When cooked rice is left at room temperature, this bacterium can proliferate and produce toxins resistant to high temperatures," says Shelley Rael, a registered dietitian and nutritionist based in Albuquerque New Mexico. In other words, "these toxins are not destroyed by reheating, which can lead to potential food poisoning if the rice is consumed," she explains.

Food poisoning symptoms often consist of stomach pain, nausea, and/or diarrhea, and usually manifest within an hour to many hours after eating spoiled food.

How long does rice last in the fridge?

For this reason, it's important to store any leftover rice in a securely sealed container, which will keep moisture out. Rice also needs to be refrigerated in a timely manner. "My rule or guideline is to cool leftover rice and get it into the fridge within an hour after preparing," Rael suggests. She adds that rice can technically safely last up to 2 hours, but shouldn't exceed that timeframe. 

If properly stored within 2 hours of being prepared, cooked rice can be enjoyed later as leftovers, though there isn't universal consensus on how long it should stay fresh. Some dieticians say that leftover rice lasts as many as 6-7 days if one's refrigerator temperature is low enough, but Great Britain's Food Standards Agency notes that leftover rice should be consumed "within 24 hours."  The U.S. Department of Health & Human Services has a Food Safety app that shows that leftover rice can be stored for "3 to 4 days." Messer recommends a similar timeframe but says "if you're unsure about the safety of the rice, it's best to be cautious and discard it after no more than 4 to 6 days." Frozen rice can last as long as 6 months.

How can you tell if rice is spoiled?

As with most foods, any unusual discoloration or strange smells coming from your rice mean your leftovers should be discarded. "Signs of spoilage include an off odor or unusual texture," says Messer. This could be a slightly sour smell or a slimy or gooey texture - both of which are indications that the rice may contain harmful bacteria.

Rael says that one needs to be especially careful when serving leftover rice to certain groups or individuals. "Exercise caution and never give leftovers to young children, those who are pregnant, or the immunocompromised if the food is older than 3-4 days."

And if you aren't sure how long it's been or don't know if it's still safe or not, it's probably best to leave it be. "When in doubt, throw it out," advises Messer.

More: Half the people on the planet eat rice regularly. But is it healthy?

This article originally appeared on USA TODAY: How long does rice last in the fridge? How to reheat leftovers safely