Many people love saving leftovers — it saves time, reduces food waste, and makes busy mornings easier. But not all foods are safe to store overnight or reheat later. Some dishes can lose their nutrients, while others can develop harmful bacteria or toxins that may cause food poisoning.
Here are the most common foods you should avoid reheating or keeping overnight — and why it matters for your health.
1. Rice
Cooked rice might seem harmless, but it’s one of the riskiest foods to reheat. Rice naturally contains spores of Bacillus cereus, a bacterium that can survive cooking. When rice is left out at room temperature for too long, these spores multiply and produce toxins that reheating won’t destroy.
What to do instead:
If you cook rice, refrigerate it within one hour of cooking and eat it within 24 hours. Reheat only once, and make sure it’s steaming hot before serving.
2. Eggs
Reheating eggs — especially scrambled or boiled ones — can cause protein breakdown that releases harmful compounds. Also, bacteria like Salmonella can grow quickly in cooked eggs if they’re left out for more than two hours.
What to do instead:
Make only what you plan to eat. If you have leftovers, store them in the fridge immediately and eat cold rather than reheating.
3. Chicken
Chicken is a protein-rich food that’s prone to bacterial growth if not stored properly. When reheated multiple times, the structure of its proteins changes, which can make it harder to digest and even cause stomach discomfort.
What to do instead:
Reheat chicken only once and ensure it’s thoroughly hot all the way through (at least 165°F or 74°C). Avoid reheating dishes like chicken curry or soup several times.
4. Potatoes
Cooked potatoes can become unsafe if left at room temperature for too long. The bacteria Clostridium botulinum, which causes botulism, can grow in cooked potatoes stored in foil or airtight containers without refrigeration.
What to do instead:
Cool and refrigerate cooked potatoes within two hours. Avoid reheating them multiple times — once is enough.
5. Spinach and Leafy Greens
Spinach, kale, and other leafy greens contain high levels of nitrates. When reheated, these nitrates can convert into nitrites and nitrosamines, compounds linked to an increased risk of cancer when consumed regularly.
What to do instead:
Eat your greens fresh. If you have leftovers, consume them cold in a salad or smoothie instead of reheating.
6. Mushrooms
Mushrooms are rich in proteins that can deteriorate quickly. When reheated, their protein structure changes, which can cause digestive discomfort or food poisoning, especially if not stored properly.
What to do instead:
Eat leftover mushrooms cold in salads or sandwiches. If reheating, make sure they’ve been refrigerated properly and are heated thoroughly.
7. Seafood
Fish and shellfish spoil rapidly and can harbor harmful bacteria like Listeria or Vibrio. Reheating seafood can not only alter its taste and texture but also increase the risk of foodborne illness if it wasn’t cooled properly.
What to do instead:
Consume seafood immediately after cooking. If you must save it, store it in the refrigerator for no more than 24 hours and reheat only once at a safe temperature.
8. Beets
Beets are another nitrate-rich vegetable. When reheated, these nitrates can form compounds that are potentially harmful to your blood’s ability to carry oxygen, especially in children.
What to do instead:
Enjoy leftover beets cold — they make an excellent salad topping or side dish without needing reheating.
9. Celery and Carrots
These vegetables are often added to soups or stews, but both contain nitrates that can transform into nitrites when reheated repeatedly. Over time, that may contribute to oxidative stress and other long-term health issues.
What to do instead:
If you’re making soups or stews, remove celery or carrots before reheating or prepare them fresh each time.
10. Pasta with Cream or Dairy Sauces
Pasta coated in dairy-based sauces, such as Alfredo or carbonara, can spoil quickly. Reheating can cause the sauce to separate and curdle, and bacteria can grow in the dairy if stored too long.
What to do instead:
Store cream-based pasta in airtight containers in the fridge and eat it within a day. Reheat only once and stir well to ensure even heat distribution.
11. Fried Foods
Reheating fried foods might make them crispy again, but it can also cause the formation of harmful free radicals in the cooking oil, especially if the oil was used multiple times. These compounds may contribute to inflammation and heart issues over time.
What to do instead:
It’s best to eat fried foods fresh. If you do reheat, use an air fryer or oven — not the microwave — to reduce oil oxidation.
12. Shellfish-Based Soups and Stews
Shellfish, like shrimp or crab, spoil extremely fast. Even if stored in the fridge, toxins can develop that reheating cannot remove. Eating leftover shellfish-based dishes can lead to serious foodborne illness.
What to do instead:
Only make enough for one meal, and discard any leftovers after 24 hours.
Final Thoughts
Leftovers are convenient, but food safety should always come first. Some foods simply aren’t meant to be reheated or kept overnight — doing so can destroy nutrients, change the food’s composition, or even lead to food poisoning.
If you love meal prepping, focus on foods that are safe to reheat, such as grains, beans, and certain vegetables. Always refrigerate within two hours, store properly, and heat thoroughly before eating.
Your health — and your peace of mind — are worth that little extra care.
