Does overnight food kill us?

Someone may have told you not to eat any overnight food even if it is stored in fridge, because it causes cancer, and you may wonder whether this is true. In general overnight food refers to the food that has been stored for hours after cooking, and here comes the question, is it safe to eat overnight food?

I think it is very important to verify this statement because many people have the habit of eating overnight food. Many white-collar workers are too busy to prepare a breakfast in the morning, therefore they may eat the leftover from last night as breakfast. Besides, when someone make a dinner for the whole family, it is possible that they don’t finish all of the food, as a result, the remaining of the food will be stored in the fridge. In fact, overnight is common among daily life; therefore, it is highly relevant to our health.

It is not doubtful that food is not edible if it stays too long at room temperature. Without any additives, bacteria grow rapidly inside the food at room temperature.  Fortunately, we have fridges that store food at low temperature so that bacteria grow slowly. However, it is possible that other species rather than bacteria may form in overnight food, and what we want to find out is whether other species form or not.

Studies have shown that nitrite is produced in cooked vegetables that are stored overnight. Many green vegetables contain nitrates, and very little amount of bacteria are needed to convert the nitrates into nitrites, and this is how nitrites forms in overnight vegetables. Nitrite is indeed a cancer-causing agent, however, studies shows that the amount of nitrites present in cooked vegetable is so small that much more is needed if it wants to become a cancer-causing agent. As a result, nitrites in cooked vegetables are not threatening to our life. Moreover, we can prevent the formation of nitrites by storing it in a vacuum container because bacteria cannot survive without air. Although it is impossible to create a perfect vacuum even if we try to suck all the air out from the container, the concentration of air still decreases significantly, and the rate of growth of bacteria will be controlled effectively after the container is stored in fridge.

fig1, nitrate composition in some vegetables. Don’t worry, this amount is far from killing someone

No evidence suggests that nitrite will be produced in overnight rice or bread, so as long as they are not moldy, it is safe to eat overnight rice or food. Overnight protein such as meat and egg does produce some nitrites, but processed meat contains much more nitrites and they are not labeled as dangerous food, therefore we do not need to worry about nitrites in overnight meat, either.

fig2, processed meat. They actually contains much more nitrites than any form of overnight food

In conclusion, the rumor of nitrites in the overnight food is cancer causing is a lie. If you are still worried about it, store the food properly will prevent any formation of nitrites.

Citings:

fig1: http://www.sheilakealey.com/dietary-nitrates-health/

fig2: http://smallbites.andybellatti.com/you-ask-i-answer-nitrates-nitrites-and-then-some/