Are Microwave-cooked foods less nutritious?

Do you have an overly health conscious neighbour or relative who makes you feel guilty for using your microwave to cook food? Do they tell you about how radiation “kills” your food and destroys the nutrients, making it less healthy? Do you wonder if they might be right? Let’s take a closer look at the facts.

One review article from the Journal of the American Dietetic Association looked at a number of studies examining the difference in vitamin retention between oven cooking and microwave cooking. The overall consensus was that microwave cooked food fared the same or better in retention of vitamins than conventional oven cooking. That is, microwaved food had the same or more nutritional value. Surprised yet?

Another more recent study from the Journal of Food Science measured how various cooking methods affected antioxidant capacity of 20 vegetables. For the less scientifically inclined, antioxidants are good for you, so losing them from your food is bad.The researchers found that microwaving, along with baking and griddling led to the least reduction in antioxidant capacity (good). Pressure cooking and boiling led to the most loss (bad).

Now there are a few possible explanations for these results. First, microwaving generally does not use as much heat and takes less time than other methods of cooking. Since many nutrients such as antioxidants are heat-sensitive (meaning that they break down when exposed to high temperatures), it makes sense that if you expose them to less heat for a shorter amount of time, there will be more remaining after cooking.

Second, antioxidants such as Vitamin C, glutathione and anthocyanins (as well as many non-antioxidant vitamins and minerals) are water soluble. When boiling vegetables, a significant amount of these nutrients are lost in the water. This is in contrast with fat soluble antioxidants such as Vitamins A, E and Beta-Carotene, which we would not expect to be lost when cooked in water. Now, this doesn’t matter so much if you are making a vegetable broth where you plan on consuming the liquid after cooking. But say you are boiling carrots. Most of us just toss the water right down the drain when we are done (along with many of the nutrients). It should be noted, however that this does not hold true if you are microwaving using water. For example, microwaved broccoli retains more than 90% of its nutritious value when cooked dry. But when microwaving with water, the nutrient losses are comparable to those seen with boiling.

So there you have it, microwaving foods does not make them less nutritious. It appears that if you want to get the most nutrition from your food, it doesn’t matter as much what device you use to cook it, just be sure to use low heat and not to cook with water.

There may still be plenty of reasons for choosing not to cook your food in the microwave; it doesn’t taste as good, it doesn’t look as good, and if you’re anything like me the outside of your food is always way too hot while the centre is still ice cold. Just don’t say it’s for nutrition.

What do you think? Do you cook with your microwave? Does this information change your mind at all?