Many people automatically associate leftovers with nitrites, cancer risks, and other health hazards, viewing them as “silent killers.” However, a health column on Sohu points out that most properly stored leftover dishes do not cause cancer. The real risks are mainly linked to four types of foods: cooked seafood, soft-boiled eggs, cold salads with black fungus, and soy milk. Improper consumption of these foods can lead to food poisoning or gastroenteritis.
Shrimp, crab, scallops, oysters, and other seafood are high-protein foods. Despite thorough cooking, bacteria can still grow if leftovers are improperly stored, even at low temperatures. Consuming these can cause nausea, diarrhea, and fever. Experts recommend eating seafood immediately after cooking, or freezing any leftovers right away.
Soft-boiled eggs, while delicious, may harbor Salmonella bacteria if not fully cooked. These bacteria can enter through pores in the eggshell and continue to multiply even in the fridge. Half-cooked eggs should be eaten the same day and should never be kept overnight.
Cold salads, though refreshing, spoil easily. Most salad ingredients are not heat-treated, and black fungus may carry parasites or bacteria. Soy milk, rich in protein, provides an ideal environment for bacterial growth. If not boiled thoroughly, residual trypsin inhibitors and saponins in soy milk can cause stomach discomfort.
Nutritionist Aguan also emphasized that the main concern with leftovers is improper storage or repeated reheating, which can allow bacteria to multiply and cause food poisoning. Many people mistakenly believe that storing leftovers in the fridge guarantees safety. While refrigeration slows bacterial growth, it does not completely kill bacteria. Leftovers stored for more than three days may still spoil.
When reheating leftovers, they must be thoroughly heated. Most bacteria are killed at temperatures above 90°C. It’s important to heat food slowly and evenly, stirring if needed. While meat dishes are less likely than vegetables or seafood to form nitrites or other carcinogens, they still must be thoroughly cooked—heating for at least 10 minutes or microwaving for over a minute is recommended.
