Can you reheat spinach?

Spinach is tasty and healthy, but there are many stubborn myths about this vegetable. Does this green treat contain as much iron as claimed? Can you heat a leftover spinach or not? And what about the combination fish and spinach again?

1. Can you reheat spinach?

Yes, you can. It is important that you let leftover spinach cool down quickly after the first preparation and keep it in the fridge at 4 to 7 degrees Celsius. This reduces the chance of bacteria that produce the potentially harmful substance nitrite to grow. Do not store leftovers of nitrate-rich vegetables in the refrigerator for longer than 2 days and do not give them to children less than 6 months old. You can also freeze spinach.

Yes, you can. It's fine to combine nitrate-rich vegetables such as spinach or lettuce with fish or shellfish, such as mussels. This can be done several times a week. The Netherlands Nutrition Center previously advised not to combine nitrate-rich vegetables, such as spinach, endive or beetroot, with fish, crustaceans and shellfish (with the exception of salmon and mackerel). This combination can cause nitrosamines to form. Nitrosamines have been associated with the formation of (stomach) cancer in animal studies. After recent studies, we know that eating these nitrate-rich vegetables does not pose a health risk. It is therefore no problem to combine fish with nitrate-rich vegetables. Moreover, it doesn't matter how often you eat nitrate-rich vegetables per week.

Stiff teeth after eating spinach is due to the oxalic acid in this vegetable. That is why purslane and rhubarb also give stiff teeth when eating. Oxalic acid reacts quickly to calcium and you can feel it in your teeth. Incidentally, the acid also binds to calcium in the food; your body can no longer use that calcium. You can prevent stiff teeth by binding the oxalic acid with a little chalk during cooking (regular school chalk is fine). It reduces stiff teeth, but does affect the taste of the spinach slightly. You can also add a little milk or cream while cooking; that helps against the rough feeling and also counteracts the descaling effect. That is also the reason that a lot of frozen spinach contains cream; the so-called spinach a la crème. Serving a hard-boiled egg with the spinach also counteracts the stiff feeling.

Fresh spinach contains 2.75 mg of iron per 100 grams. Cooked spinach contains 3.57 mg per 100 grams. This means that the vegetable does indeed contain a relatively large amount of iron; about as much as beef. However, when we look at how this iron is absorbed into the body, it is disappointing. Iron occurs in our diet in two forms: heme iron and non-heme iron. Heme iron is mainly found in meat and fish and is well absorbed by our body. Vegetables, fruit, bread, potatoes and grain products mainly contain non-heme iron. And this variant is less efficiently absorbed by our body. The aforementioned oxalic acid in spinach makes absorption even more difficult, because it binds to iron. The fact that spinach's iron content is often overestimated is because a mistake was made in determining it. German scientists analyzed the vegetable in 1937 and found that its iron content was ten times lower than previously thought. How this could have happened is unknown. One theory is that dried spinach was used in the first analysis. Another is that the previous researcher put the comma one place too far to the right, causing the iron content to be ten times higher. Incidentally, recent research shows that eating a plate of spinach does make muscles work more efficiently. Spinach is a healthy vegetable anyway. In addition to iron, spinach is rich in potassium, calcium, phosphorus and magnesium, as well as in vitamin A, vitamin E, folic acid and antioxidants such as lutein and zeaxanthin.

Spinach contains a lot of moisture, which evaporates during preparation. For 250 grams of cooked spinach you have to count 450-500 grams of raw spinach per person, according to the Nutrition Center.