Heating meals in the zapper helps retain more vitamins than almost any other cooking method. But, as nutritionist Marcela Cosentino explains, there are some foods that should never be left to the mercy of the microwave.

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Meat. After six minutes of thawing meat in the microwave, you will have burnt away 50 percent of the vitamin B12. If you do reheat those delicious meaty leftovers, only leave them in for less than two minutes. Otherwise, it will dry up and degrade the protein.

White rice. This is not a microwavable food. “The microwave’s high temperature strips nutrients from the grain. It is better to cook rice in a pot of water, where a gradual temperature is achieved as time goes on. At first, the water is warm and then heated. In contrast, the microwave maintains a consistent temperature from the start of cooking,” says the nutritionist.

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Oranges. Under no circumstances heat an orange in the microwave. You will negate the benefits of its vitamin C content because it is a particularly heat sensitive vitamin.

Broccoli. A study in the “Journal of the Science of Food and Agriculture” found that broccoli cooked in the microwave, with a little water, reduced antioxidants by up to 97 percent but when steamed, this figure was just 11 percent.

Garlic. Less than 60 seconds in the microwave is sufficient to nullify alliinase, the active ingredient that makes garlic an anticarcinogenic.

Milk. Avoid heating it in this type of oven. You will zap away nearly half of its nutrients and completely eliminate vitamin B12. A study by Richard Quan, scientific Division of Gastroenterology and Nutrition, Department of Pediatrics, University of Texas, showed that heating human breast milk in a microwave oven reduces its immunological properties. 

Margarine or butter. Its molecules are crystallized and resistant to microwave rays. “If you apply a longer cooking time to make the butter melt, you strip its protein value with the heat,” says Cosentino.

Asparagus. Placing them in this apparatus would result in a considerable reduction of their vitamins,” says the nutritionist.