The opinion that spinach should not be reheated persists. However, one cannot say so in general terms.
That’s why reheating spinach is potentially dangerous
One of the main reasons reheating spinach is discouraged is because of the nitrate ingredient.
In itself, nitrate is harmless to humans. However, babies cannot tolerate the ingredient and can develop blue fever if they eat spinach. It becomes problematic if the spinach is left at room temperature for a long time. Then the nitrate can be converted into nitrite.
In connection with proteins, so-called nitrosamines, which are considered carcinogenic, can be formed. Because of this fact, you should definitely refrain from reheating unchilled spinach.
You can still reheat your spinach this way
However, if you keep the spinach in the fridge, you can safely reheat it the next day.
If you have leftover spinach, cover it with cling film and put it in the fridge as soon as possible. Then you can warm it up the next day without hesitation.
However, you should not keep the spinach for longer than a day, even under these conditions.
You should also reheat it at most once, not more often.
