Certain foods can become unsafe when stored overnight due to bacterial growth or chemical changes. Mushrooms and wood ear fungus “should be eaten the same day they’re cooked,” as their proteins and nitrates can turn into harmful compounds if stored too long or reheated.

Leafy greens like spinach also lose nutrients and become risky when left at room temperature — “nitrite levels increase and vital nutrients are lost.” Proper refrigeration is essential to keep them safe.

Soy-based foods such as tofu and soy milk “can quickly become breeding grounds for bacteria” because of their high protein and moisture content. In severe cases, poor storage may lead to Clostridium botulinum contamination, which can cause paralysis or even death.

Soft-boiled eggs and seafood are equally unsafe to store overnight due to toxin formation and rapid bacterial growth.

To stay safe, experts recommend keeping leftovers below 4°C (39°F), using airtight containers, eating them within 24 hours, and reheating only once. As the article stresses, following these simple steps “helps keep leftovers safe and your meals nutritious.”