All of us, very often prepare meals for several days and subsequently re-heat them. However, some foods change their composition and lose their nutritional properties, and even become toxic. Here's what some of these are :
Mushrooms are best consumed immediately after preparation, and if they stay for another day, it is better to eat them cold. This is true for soups, as well as for risotto, which are made with mushrooms. While re-heating mushrooms there is a change in the composition of protein, and even a change of taste in food. They then cause a variety of digestive problems, and lose their health benefits.
Just as with mushrooms, with re-heating meat there is a change in the composition of proteins. It is therefore not advisable heating at high temperatures, especially chicken, which contains more protein than red meat. If you heat it, you better put it on a lower temperature and heat it longer.
Potato is a highly nutritional food which we should not re-heat because it loses most of its properties if re-heated and even becomes toxic. Eat it immediately after preparation or even cold - then it is the highest percentage of resistant starch meritorious for long-lasting feeling of satiety, If you are preparing stews for several days, take the potatoes and add them subsequently.
Spinach is a food with a high percentage of nitrates, re-warming turns them into nitrites. They have the potential to cause cancer to the body, so make sure to eat only fresh spinach ie. immediately after preparation.
Like Spinach, beetroot also contain nitrates that becomes extremely harmful after re-heating. Its is best not to re-heat it.
Celery, which is most commonly used while preparing soups, should be removed after cooking, along with carrots and consumed freshly prepared. It also contains nitrates. You can re-heat the soup if you remove celery and carrots.
Eggs are at high risk after re-heating. They also become toxic due to exposure to high temperature. It does not apply to foods where eggs are involved in sauces such as bechamel sauce, but refers to dishes with boiled or fried eggs.