(WKBN) — Holiday leftovers cause about 400,000 cases of post-Christmas illness in America.

If they aren’t eaten in two to three days, it can become harmful to one’s health.

“Upset stomach, all those things. That’s mild, but the more the bacteria grows on it — you won’t see it all the time — the worse it’ll make you sick,” said Trumbull Regional Medical Center nutrition services director Robert Rose.

Different leftovers last different amounts of time depending on what type of food they are, there’s also proper ways to store them to make sure they last just a little bit longer.

“Turkey and ham, those can usually last for the couple of days because of the salt and all that stuff in it. Vegetables, potatoes, you want to get rid of those first,” said culinarian Becca Albani.

That’s because bacteria can grow on vegetables and potatoes easier. Another tip for hot foods — don’t place them in the refrigerator while they’re warm.

The temperature change can also cause bacteria to grow.

On storing leftovers, Albani said, “Nice, tight Tupperware containers, Zip-loc bags that don’t have any holes in them,” will help keep food safe.

They will also keep the food fresher. Storing leftovers at the proper temperature is also crucial.

“You have to get everything down to 70 degrees in 4 hours and in 6 hours, it has to reach 40 degrees. Cool things in shallow pans so that it gets cooler quicker, and that’s the way you can store it,” Rose said.