Reheating These Foods Could Make You Sick | Keck Medicine of USC

Reheating These Foods Could Make You Sick

Warming last night’s dinner is easy and convenient, but do you know how to avoid the health risks?

The only thing worse than the diarrhea and vomiting that accompany food poisoning is knowing that you could have avoided it by practicing better food-safety habits.

Even if you’re in a hurry and reheating food on the fly, you’ll want to be sure to follow these guidelines to avoid getting sick:

  • Wash your hands and the surfaces in your kitchen with dish detergent, often, to avoid cross contamination of foods.
  • Follow Food and Drug Administration (FDA) guidelines, when reheating leftovers. Heat food to at least 165 degrees and bring sauces, soups and gravies to a boil.
  • When in doubt, throw it out. Contaminated food doesn’t have to look or smell funny to be bad.
  • Don’t assume that your microwave will zap bacteria. Microwave ovens cook unevenly, overcooking some spots and leaving some cold. It’s the cold areas, where bacteria thrive.

Additionally, the following foods are more susceptible to contamination:


Chicken naturally contains salmonella, but these deadly bacteria are destroyed by heat. When the meat cools, they can begin growing again. If you are reheating chicken, make sure that it is piping hot before serving. You can rotate it in the microwave or oven, if needed, for even cooking.

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Never leave cooked rice out at room temperature or carry it in a packed lunch without an ice pack. That’s because naturally occurring bacteria, Bacillus cereus, continue to grow even after rice has been cooked. Rice should go straight into the cool refrigerator for storage and directly to the oven or microwave for reheating.

Beets, Spinach, Carrots, Celery

Dense, starchy vegetables have high concentrations of nitrates, which are vital anti-inflammatories that calm blood vessels and increase blood flow. However, cooking at high temperatures turns these nitrates toxic by releasing carcinogens. It’s not known whether these carcinogens can cause cancer; current research studies have had mixed results.

Of all vegetables, potatoes are susceptible to botulism, which can turn your digestive tract topsy-turvy. The warm temperatures of microwaving promote its growth; so does leaving oven-baked potatoes wrapped in foil on the counter. Eat immediately and refrigerate leftovers as soon as possible to avoid getting sick.

by Heidi Tyline King

Interested in learning more about healthy eating and digestive issues? Consider consulting with some of the country’s top specialists at the USC Digestive Health Center, a recognized leader in the care of gastrointestinal (GI) diseases. If you are in the Los Angeles area, be sure to schedule an appointment, by calling (800) USC-CARE (800-872-2273) or by visiting