It is really unsafe for your wellbeing to warm the spinach, you should never do that. It is recommended to eat it directly after its preparation. Why? The spinach contains a high rate of nitrates which are transformed into nitrites when you warm it. This means that spinach after being warmed is carcinogenic for your body.
Celery is mostly used for the preparation of soups. The celery contains nitrates as the spinach, which means that when it is warmed the nitrates transform into nitrites. It is better to take the celery out of the soup if you want to warm it, the same thing is with the carrots.
The potatoes have many useful properties, which makes them very good for your wellbeing, but if you let them stay for a day or to, and get cool, they can lose those properties, and their dietary quality. If it comes to that, they can be very dangerous for the body, not useful at all.
The eggs can be lethal if you present them to high temperatures and warm them. If eggs are incorporated during arrangement process, they are not lethal. It only goes for reheating fried and boiled eggs.
If you eat the chicken the following day, after being prepared, it is exceptionally dangerous. You can make yourself some digestive problems, because the structure of proteins changes the next day. This is very concerning because the chicken contains much more protein that red meat. It is recommended to eat the chicken cold. But if you must warm up the chicken, be sure that you do that on a low temperature for a long period.
Mushrooms are the most risky nourishment when you reheat them. It is highly recommended to eat them directly after you prepare them. If you eat them the next day, be sure that you eat them cold. Heating up the mushrooms can make you digestive problems, even some heart problems.
You must be careful what sorts of leftover foods you put in the oven or in the microwave. You must think that the dinner you want to reheat does not contain any of these listed products. If think of reheating any of these foods, simply consider the potential wellbeing dangers of doing the same.