7 Foods You Shouldn’t Eat As Leftovers

From the iconic post-Thanksgiving turkey sandwich to repurposing last night’s takeout, leftovers are more than just a convenience—they're a cultural staple. But there’s a dark side to eating leftovers: food poisoning. And unfortunately, some foods put you at higher risk than others. Here’s what you need to know.

Key Takeaways

• Not All Leftovers Are Safe: Some foods, such as rice, potatoes, and leafy greens, can develop harmful bacteria or toxic compounds when stored or reheated improperly.
• Proper Storage is Critical: Refrigerate leftovers within two hours, use shallow containers for even cooling, and label with dates to keep track of freshness.
• Reheating Right: Always reheat food to an internal temperature of 165°F (74°C) and avoid reheating the same food multiple times to minimize bacterial growth.

The Hidden Dangers Lurking in Your Leftovers

In today’s fast-paced world, leftovers are the ultimate time-saver. Busy schedules mean that cooking from scratch every night isn’t always feasible. Leftovers offer an easy, quick solution for meals on the go. But how safe are they?

Getting sick from eating leftovers is relatively uncommon if proper food safety practices are followed, but when mistakes happen the risk of foodborne illness, more commonly known as food poisoning, increases significantly.

The Centers For Disease Control (CDC) estimates that about 48 million people in the U.S. get sick from foodborne illnesses every year, with 3,000 deaths and 128,000 hospitalizations. While not all of these cases are from leftovers, improper food storage and reheating are common causes. For example, not refrigerating or freezing leftovers quickly can increase risk. Leaving food out at room temperature for more than two hours—or one hour if the room is over 90 degrees Fahrenheit—allows bacteria such as Salmonella and E. coli to multiply rapidly. So can storing leftovers in large, deep containers, which can prevent them from cooling evenly and creating pockets where bacteria grow.

Inadequate reheating is also a culprit. Reheating food to a temperature below 165°F (74°C) doesn’t kill harmful bacteria, especially in dense foods like casseroles or stews.

The Worst Offenders

Reheating leftovers is a common practice, but some foods can become unsafe or unappetizing when reheated due to changes in their chemical composition or the growth of bacteria. Here are the top seven foods you shouldn’t eat as leftovers and why:

• #1 Eggs: Reheating cooked eggs (scrambled, boiled, or fried) can cause them to release toxic compounds and become rubbery or sulfurous in taste. There’s also a risk of Salmonella if they aren’t reheated properly.
• #2 Beets: Beets are rich in nitrates, which are beneficial for blood pressure regulation and circulation. However, when beets are cooked and then stored, the nitrates can convert into nitrites over time. Upon reheating, nitrites can further convert into nitrosamines, compounds that have been linked to an increased cancer risk in some studies. This is primarily a concern if beets are left at room temperature too long or reheated multiple times.
• #3 Potatoes: Potatoes, especially when cooked and left at room temperature for extended periods, create an ideal environment for Clostridium botulinum, a bacteria that causes botulism—a rare but serious illness that affects the nervous system. Even reheating might not destroy botulism once it’s formed. But that’s not all… The common cooking practice of wrapping baked potatoes in aluminum foil and leaving them out traps moisture and prevents air circulation, promoting bacterial growth. How can you protect yourself? One way is to refrigerate cooked potatoes within two hours and avoid reheating them if they’ve been left out longer.
• #4 Spinach and Leafy Greens: Leafy greens also contain nitrates that can convert into nitrites and nitrosamines when reheated, compounds that may be carcinogenic. This is especially risky for infants and young children.
• #5 Rice: Cooked rice can harbor Bacillus cereus, a bacteria that produces toxins when rice is left at room temperature for too long. "What makes B. cereus particularly tricky is that reheating won't destroy its toxins once they've formed," explains Dr. Emily Chen, a food microbiologist at Stanford University. The bacteria multiply rapidly at room temperature, which is why rice needs to be cooled quickly after cooking and refrigerated within one hour.
• #6 Chicken: Chicken has a high protein content that can change structurally when reheated, making it harder to digest and sometimes leading to stomach discomfort. If not reheated to 165°F (74°C), it can also harbor Salmonella or Campylobacter bacteria. If you must reheat chicken, do it slowly and ensure it’s piping hot all the way through.
• #7 Seafood: Seafood can spoil quickly and contains proteins that deteriorate when reheated, leading to a fishy odor and potential histamine poisoning or scombroid food poisoning if not handled properly. If reheating seafood, ensure it reaches an internal temperature of 145°F (63°C), but ideally, eat it fresh.

How To Protect Yourself

• Cool Quickly: Refrigerate leftovers within 2 hours of cooking. Divide large portions into shallow containers to cool evenly.
• Store Properly: Keep the fridge at 40°F (4°C) or below. Label leftovers with dates and aim to eat them within 3-4 days.
• Reheat Thoroughly: Heat leftovers to an internal temperature of 165°F (74°C). Stir food during reheating to ensure even warmth.
• Don’t Reheat Multiple Times: Only reheat the portion you plan to eat. Repeatedly cooling and reheating increases bacterial growth.
• When in Doubt, Throw It Out: If leftovers smell off, have an unusual texture, or have been sitting for too long—don’t risk it.

Summary

Leftovers are a convenient part of modern life, but they’re not always as safe as they seem. Improper storage, cooling, and reheating can turn yesterday’s meal into a breeding ground for harmful bacteria like Salmonella, E. coli, and Bacillus cereus. Foods like eggs, rice, and potatoes are particularly risky when mishandled. Understanding the proper ways to store and reheat leftovers is essential to avoid foodborne illnesses and keep your meals both tasty and safe.

Frequently Asked Questions

• Is it safe to eat leftovers every day? Yes, as long as leftovers are stored properly, refrigerated within two hours, and reheated to the correct temperature.
• How long can I keep leftovers in the fridge? Most leftovers should be eaten within 3-4 days. After that, the risk of foodborne illness increases.
• What’s the safest way to reheat leftovers? Reheat leftovers to an internal temperature of 165°F (74°C), stirring food halfway through to ensure even heating.
• Why is reheating rice dangerous? Cooked rice can harbor Bacillus cereus, a bacteria that produces heat-resistant toxins if rice is left at room temperature too long.
• Can I reheat leftovers multiple times? It’s best to reheat leftovers only once. Repeated cooling and reheating increase the risk of bacterial growth.