The hazards of microwave cooking: fact or fiction?

Post by Emily White 

Almost every home in New Zealand has a microwave oven. They are convenient, quick and easy. But despite all of this many people have doubts as to how safe microwave ovens are. Many people believe that microwaves 'zap' the nutrients out of food or even change the structure of food and water to make it unfit for human consumption. Therefore it seems an appropriate question to ask, how safe are microwave ovens? 

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It appears that today with the widespread use of the Internet where anyone can post their opinions for all to see, there appears to be a greater fear instilled in people of anything technological or 'mainstream'. Now don't get me wrong- I am a firm believer in that with a lot of things nature does get it right, but nowadays we appear to be so quick to disregard anything technological without any evidence based research. This approach can be both naive and cynical.  

Cooking food in general, whichever method, has a complex effect on the nutrition status of food. In some cases, cooking can actually increase nutrient content- for example carotenoids in carrots or lycopene in tomatoes (1). However in most cases heating or cooking food can break down the vitamins and other nutrients within it. Studies have shown that the three most important variables when determining the effect cooking has on food are, the intensity of the heat, the duration of heating, and contact with water (2).

Therefore it seems a no brainer that boiling vegetables can be the most detrimental to nutrient content. This is confirmed in a study that looked at different cooking methods and the antioxidant nutrition status. This study showed that microwave cooking along with baking, caused the lowest losses of nutrient status, whereas showed boiling to be the worst (3)

The studies that people claim prove that microwaving is the worst method can be somewhat misinformed. For example there was a study done that looked at the phenolic compound content of broccoli after cooking and suggested microwaving to be the worst method for preserving nutrients. However in this study, the broccoli was microwaved with water- thereby essentially just boiling it in the microwave. Using this method the broccoli lost 74-97% of its antioxidants- no wonder people become terrified of microwave use! (4).  However when cooked in the microwave without water or through steaming- the broccoli had very little nutrient loss (5). Therefore it is important to note, if you are going to microwave your vegetables, do so without water in order to minimize nutrient losses. 

It is extremely important to do your research and look for evidence when forming an opinion. There is a lot of misleading information on the Internet today and microwave-cooking methods have definitely fallen victim to this. The current evidence today is that using a microwave can be the best way to cook your vegetables in order to minimize the breakdown of nutrients and this is partly due to the faster cooking time over other methods. 

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​References:
1. Miglio, C., Chiavaro, E., Visconti, A., Fogliano, V., & Pellegrini, N. (2008). Effects of different cooking methods on nutritional and physicochemical characteristics of selected vegetables. J Agric Food Chem, 56(1), 139-147. doi: 10.1021/jf072304b

2. Schnepf, M., & Driskell, J. (1994). SENSORY ATTRIBUTES AND NUTRIENT RETENTION IN SELECTED VEGETABLES PREPARED BY CONVENTIONAL AND MICROWAVE METHODS. Journal of Food Quality, 17(2), 87-99. doi: 10.1111/j.1745-4557.1994.tb00135.x
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3. Jimenez-Monreal, A. M., Garcia-Diz, L., Martinez-Tome, M., Mariscal, M., & Murcia, M. A. (2009). Influence of cooking methods on antioxidant activity of vegetables. J Food Sci, 74(3), H97-H103. doi: 10.1111/j.1750-3841.2009.01091.x

4. Vallejo, F., Tomás-Barberán, F. A., & García-Viguera, C. (2003). Phenolic compound contents in edible parts of broccoli inflorescences after domestic cooking. Journal of the Science of Food and Agriculture, 83(14), 1511-1516. doi: 10.1002/jsfa.1585

5. Natella, F., Belelli, F., Ramberti, A., & Scaccini, C. (2010). MICROWAVE AND TRADITIONAL COOKING METHODS: EFFECT OF COOKING ON ANTIOXIDANT CAPACITY AND PHENOLIC COMPOUNDS CONTENT OF SEVEN VEGETABLES. Journal of Food Biochemistry, 34(4), 796-810. doi: 10.1111/j.1745-4514.2009.00316.x