Do microwaved foods lose their nutrients?
The myth that microwaved foods lose more nutrients is one of the most popular myths in our culture.
Many claim that this is because food loses vitamins and nutrients when cooked in the microwave.
However, this idea that microwaves are worse than other forms of cooking has no scientific basis, the BBC’s Trust Me, I’m a Doctor explains on its website.
Microwaves cook food using energy waves that are similar to radio waves, but shorter.
These waves are very selective and affect mostly water and other molecules that are electrically asymmetric: positively charged at one end and negatively charged at the other.
Microwaves cause these molecules to vibrate and generate heat that then spreads to nearby molecules to heat, and cook, the food.
This process can affect the vitamins and nutrients in the food, but these changes are not unique to microwave cooking, but are a result of the heating process. When food is heated, some vitamins, such as vitamin C, are broken down, Harvard University explains on its medical and health information website.
But this happens regardless of whether the food is heated in a conventional oven, on a stove or in a microwave. Proteins also “denature” (i.e. they break down and sometimes lose their properties) when they are heated, by whatever means.
But because preparation times are shorter, microwave cooking actually helps preserve vitamin C and other nutrients.
Cooking with water
Nutrients in food are also lost when food is cooked with water. Several scientific studies have concluded that when vegetables are boiled, most of their nutrients are released into the water.
Vitamin C and many of the B vitamins, such as B6 and B12, are more vulnerable because they are water soluble. And normally that water is not used, but is discarded after cooking, so the nutrients in it are also lost.
The loss of nutrients is greater with boiling than with other cooking techniques, such as microwaving, frying or steaming. So the best way to retain vitamins and nutrients in food when cooking is to use short cooking times that limit exposure to heat, and a cooking method that uses as little liquid as possible.
A 2009 paper published in the Journal of Food Science concluded, for example, that microwave cooking maintains antioxidant levels in foods such as beans, asparagus or onions better than boiling, pressure cooking or baking.
To recap: the best way to use the microwave is to minimize the amount of water and not overcook the vegetables. However, if you’re more concerned about maintaining the nutritional value of the food, steaming is the best way to go. In addition, there are other things you can do to preserve as much of the nutritional value of the food as possible.
Useful tips to prevent nutrient loss in cooking
Peel and cut the food just before preparing or consuming it.
Use short wash times before cooking.
Use cooking methods in which water and food come into contact as little as possible.
Wait for the water to come to a full boil before immersing the food, as this will reduce the cooking time required.
Cook vegetables al dente and cool them after cooking to preserve their vitamins.
Use the water from cooked vegetables to make other foods, such as soups.
Avoid storing fruits and vegetables in the refrigerator for long periods of time.
The addition of vinegar or lemon juice helps to preserve vitamins and the absorption of some minerals, such as iron (although it can also change the taste).