There are two approaches to addressing the presence of day-old, room-temperature pizza.
On one side, you have the food scientists, the medical community, and the United States Department of Agriculture (USDA). On the other, you have literally everyone else.
It's not hard to guess which side says you have to refrigerate it or pitch it.
Experts tell us what to do with leftover pizza.
The official stance on food safety begins with something the USDA Meat and Poultry Hotline calls, maybe a little dramatically, the "Danger Zone." You do not want to take a ride into this Danger Zone, not even if you are Kenny Loggins and Tom Cruise combined. (Because, diarrhea.)
The food safety Danger Zone is the temperature range between 40 and 140 degrees. Hot food should stay above 140 degrees. Cold food should stay below 40 degrees. Otherwise, you are on a highway to...you know.
Of course, you have to serve the food, which means it will stay at room temperature during your meal. What about that, USDA?
Apparently, food can stay safe in the Danger Zone for a two-hour timeframe. If you leave perishable food out for more than two hours at room temperature, you should throw that food away, according to the experts.
Even if that food is pizza.
What We Really Do With Leftover Pizza
The other argument is less scientific. It's simply this: "I do it all the time."
Some people live on day-old pizza for years. Those same people probably reserve the refrigerator for a mostly empty bottle of ketchup. And though doctors tell them they are rolling the dice with their health, these people are not prone to food poisoning.
So what gives?
Food safety experts would say these people are just lucky and that their luck is likely run out eventually.
Writing for the University of Nebraska-Lincoln Institute of Agriculture and Natural Resources, registered dietician Alice Henneman warns of just how many bacteria could be sitting on that slice of pepperoni come morning.
"Just ONE bacterium, doubling every 20 minutes, can grow to over 2,097,152 bacteria in 7 hours," she writes (her caps).
Even worse, some food-borne pathogens develop toxins that resist heat, so reheating leftovers won't get rid of them. Staphylococcus aureus, or staph, is one of these, and it lives all over the human body.
A staph infection can mimic what people call the stomach flu with grotesque accuracy; it's what we usually mean when we say we have food poisoning, and it is not a pleasant experience.
In general, we're against gambling with our health and suppose we have to come down on the side of the experts, so think twice about eating perishables that sat out all night.
Who's getting food poisoning?
Our iron-stomached friends might beat the odds when they eat day-old pizza, but plenty of people don't.
The Centers for Disease Control and Prevention (CDC) says that one out of every six people in the U.S. gets food poisoning. According to the CDC, that adds up to 48 million Americans per year. Of these, 3,000 actually lose their lives to the infection.
Bacteria thrive at room temperature. We do not thrive on bacteria. Try tacking this sign on your bedroom door: "Do not enter unless the pizza is in the fridge."
It could save you a lot of the worst kind of distress, which is intestinal. Don't turn your gut into the real danger zone.