Microwaving kills health benefits

Broccoli loses as much as 97% of some antioxidants when microwaved.

Certain methods of preparation and cooking can cause vegetables to lose their cancer-fighting compounds according to new evidence published in the Journal of the Science of Food and Agriculture.

A study investigating various cooking methods of broccoli concluded that microwaving is the clear loser: microwaved broccoli had lost 97%, 74% and 87% of three major antioxidant compounds*. By stark comparison, steamed broccoli had lost only 11%, 0% and 8%, respectively, of the same antioxidants.

Dr Cristina Garcia-Viguera, co-author of the study, explains these results: “Most of the bioactive compounds are water soluble; during heating they leach in a high percentage to the cooking water, reducing their nutritional benefits in the foodstuff. Because of this it is recommended to cook vegetables in the minimum amount of water (as in steaming), in order to retain their nutritional benefits.”

This discovery is supported by evidence from another study being published simultaneously in JSFA. Researchers in Finland, VTT Biotechnology, observed the effects of preparation and storage upon various bioactive compounds in frozen vegetables. They found that the blanching of vegetables prior to freezing caused losses of up to a third of their antioxidant content. Dr Riitta Puupponen-Pimiä, co-author of the study, pointed out that the effects of blanching were largely plant species-dependent. Slight further losses occurred during frozen storage, though most bioactive compounds, including antioxidants, were quite stable during storage.

Antioxidant compounds, which are naturally prevalent in many vegetables, have protective effects within the body, eliminating harmful free radicals. Free radicals are highly volatile molecules that damage the DNA of cells and can cause serious diseases such as cancer and heart disease. While a healthy diet should contain more than enough antioxidants, how food is prepared and cooked may be just as important as what is eaten.