Certain foods can become unsafe when stored overnight due to bacterial growth, chemical changes, or nutrient loss. Some are particularly vulnerable and should be consumed fresh or stored with extra caution. Improper refrigeration or reheating practices can significantly increase health risks.

Mushrooms and wood ear fungus are best eaten on the same day they’re cooked. These foods contain complex proteins and high nitrate levels that, when stored too long, can convert into harmful compounds. Reheating them may also irritate the digestive system or cause more serious reactions.

Leafy greens, especially those high in nitrates like spinach, degrade in both safety and nutritional value when left at room temperature. Over time, nitrite levels increase and vital nutrients are lost, making them less healthy and potentially risky to eat if not stored properly.

Soy products like tofu and soy milk, rich in protein and moisture, can quickly become breeding grounds for bacteria. In some cases, improper storage can lead to contamination with Clostridium botulinum, a dangerous bacterium that can cause nerve paralysis or death. Similarly, soft-boiled eggs and seafood are high-risk and should not be stored overnight due to potential bacterial growth and toxin formation.

To prevent foodborne illness, always store leftovers below 4°C (39°F), use airtight containers, and limit storage to 24 hours. Reheat only once, as repeated heating degrades both food quality and safety. Following these practices helps keep leftovers safe and your meals nutritious.