The fast-paced living that modern life imposes on more and more people has made meal-prep a thing for many. The reason why is because preparing your meals in advance and them use them in the days to come saves time. However, what many aren’t aware of is that not every food can be reheated or kept overnight because they can develop harmful bacteria or release toxic compounds that put your health at risk.

Below are 5 foods you should never reheat or keep overnight no matter how tempted you are to consume them the following day.

1. Leafy Greens (Spinach, Celery, Lettuce)

You are likely well-aware that leafy greens are healthy additions to your diet. However, keep in mind that they should never be reheated. If you wonder why, here’s why. Leafy greens are rich in nitrates that can convert to nitrites and nitrosamines when exposed to high heat, compounds linked to cancer and other health issues.

If you still want to eat your leftover leafy greens, just have them cold.

2. Rice

Reheating rice might seem harmless, but it can actually pose a serious health risk if not handled properly. Cooked rice can contain spores of Bacillus cereus, a bacterium that survives cooking. When rice is left at room temperature, these spores multiply and produce toxins reheating won’t destroy that cause nausea, vomiting, and diarrhea. Just to be safe, always cool rice quickly (within an hour), store it in the fridge, and reheat only once until steaming hot. Ideally, eat it within 24 hours or turn it into fried rice right away.

3. Eggs