Dear Shyam Swaraj, sorry for the delay in replying to your question. Firstly, reheating any cooked food makes it harder to digest. Undigested food is one of the most common sources of toxins in the body.
Microwave oven is not any safe, though we are getting very used to it. In case you have to use it occasionally, please use non-plastic containers because plastic leaches it’s toxic constituents into the food. This is true for all kinds of plastics.
Thank you for your interest in the subject. Best wishes Krpa