Food poisoning, also called foodborne illness, is caused by harmful organisms, such as bacteria, viruses and parasites, in contaminated food. Symptoms of food poisoning, which can start within hours of eating contaminated food, often include nausea, vomiting and diarrhea.
Fortunately, most cases of food poisoning can be prevented with proper food preparation and cooking, and how leftovers are handled. Leftovers can be kept for three to four days in the refrigerator. After that, the risk of food poisoning increases.
Because bacteria typically don't change the taste, smell or look of food, you can't tell whether food is dangerous to eat. So if you're in doubt about the safety of leftovers, it's best to throw them out.
Learn more about handling leftovers safely from Katherine Zeratsky, a Mayo Clinic registered dietitian nutritionist.