The Healthiest Way to Cook Vegetables

David Mendosa Health Guide May 03, 2009
  • Imagine my surprise when I read a new research report that the healthiest methods for cooking veggies seem to be microwaving or cooking on a flat metal surface without any oil. After all, on the Internet we can find thousands of diatribes on the dangers of microwave cooking. Several of my friends have junked their microwaves or given them away to people they don't like.

    Researchers at the University of Murcia and Madrid's University of Complutense in Spain examined how six different cooking methods affected the antioxidant activity of 20 different vegetables. We get most of our nutritional antioxidants from vegetables and fruit. They may prevent cancer and other diseases.


    The six cooking methods were boiling, pressure-cooking, baking, microwaving, frying, and cooking without oil, which they called griddling. The vegetables were artichokes, asparagus, beets (beetroot), fava beans (broad beans), broccoli, Brussels sprouts, carrots, cauliflower, celery, corn (maize), eggplant, garlic, green beans, leeks, onions, peas, green peppers, spinach, Swiss chard, and zucchini.

    The Spanish scientists published their findings as "Influence of Cooking Methods on Antioxidant Activity of Vegetables" in the April 2009 issue of the Journal of Food Science, a publication of the Institute of Food Technologists. The free full-text of the article is online.

    "Depending on the vegetable in question, griddling and microwave cooking produced the lowest losses, while pressure-cooking and boiling lead to the greatest losses," the study concluded. "In short, water is not the cook's best friend when it comes to preparing vegetables."

    Cooking anything at more than about 115 to 118 degrees destroys their enzymes, according to many raw food fans. So you can imagine my further surprise when I read in this new study that some of the vegetables that they cooked actually increased their antioxidant levels.

    The safest vegetable to cook is the artichoke. No matter what cooking method the Spanish scientists subjected this tasty thistle to they couldn't detect any loss of nutrients.

    In fact, all cooking methods increased antioxidant levels of celery and carrots. All methods except boiling increased antioxidant levels of green beans.

    The scientists tested their fat-soluble (lipoperoxyl) and water-soluble (hydroxyl) radical scavenging capacity. Vegetable have both types of antioxidant compounds, which function synergistically.

    In terms of fat-soluble radical scavenging, microwave cooking works best for eggplant, corn, pepper, and Swiss chard, all of which significantly increase their capacity. Artichoke, asparagus, garlic, onion, and spinach keep the same capacity that they have in raw form. Fava beans and beets lose 5 percent and 30 percent of their fat-soluble scavenging capacity respectively. The worst vegetable to microwave in terms of fat-soluble radical scavenging is cauliflower, which loses more than half of its capacity.

    In terms of water-soluble radical scavenging, microwave cooking works best for celery, which significantly increases its capacity. Beets, broccoli, carrots, eggplant, garlic, green beans, leek, corn, and peas keep essentially the same capacity that they have in raw form. The worst vegetables to microwave in terms of water-soluble radical scavenging are peppers and Swiss chard, which lose 30 percent or more of their capacity.


  • Those of us who have diabetes and know that we need the best possible nutrition will appreciate these new findings. But don't expect the scaremongers on the Web to write about this study any time soon. This news is just too good for them to like.