One of the benefits of spinach is that it can be eaten raw or cooked and aside from being high in iron, it’s high in nitrates. When you reheat it, nitrates can turn into nitrites, which is a mixture of nitrogen and oxygen, which can cause health problems, such as cancer. That is if you make it a habit of reheating spinach in the microwave, so instead of reheating it, eat it raw or simply throw it away. No one likes reheated spinach anyways.
People love mushrooms and sometimes you can overdo it when you cook the entire basket and have leftovers. Reheating mushrooms can cause the proteins to deteriorate and create digestive and even heart problems. So, it’s best to cook these in small quantities, so you won’t have any leftovers. They taste better fresh anyways.