Is it true that reheating spinach is dangerous for your health?

My grandmother, my mother and others have always taught me this: reheating (in oven, microwave, pan, pot, …) prepared spinach is not good for health because it would release carcinogenic substances.

Note: this would only happen during reheating, not during the first hot preparation. Is this correct ???

Asker: Christel, 63 years old


Hello Christel,

Spinach should not be heated a second time. Spinach is high in nitrates. When you prepare spinach, it is best to drain the cooking liquid. In this way you also remove part of the nitrates. Heating nitrate-rich vegetables several times promotes the conversion of the nitrates into nitrites. Nitrites ensure that there is less oxygen uptake. It is therefore not recommended to give nitrate-rich vegetables to babies younger than six months.
Nitrites can then be converted into nitrosamines in the stomach and intestines. Studies on rats have shown that these nitrosamines are strong carcinogens, but this has never been proven in humans. Likewise, fish in combination with spinach would not be advisable because of the possibility of the formation of nitrosamines.
If you still want to reheat spinach, it is recommended to put the spinach in the refrigerator without cooking liquid after the first use (and not just store it at room temperature).

As with many things, I think ‘eat in moderation’ is the message. Don’t exaggerate in eating nitrate-rich vegetables, but you certainly don’t have to ignore them either.

You can also find an analogous question with an answer via the link:

Answered by

Lic. Dr. Physics Natasja Duhayon

Semiconductor technology, nanotechnology, microelectronics, physics, patents

Kapeldreef 75 3001 Leuven


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