July 1st, 2010
11:08 AM ET
As a feature of CNNhealth.com, our team of expert doctors will answer readers' questions. Here's a question for Dr. Gupta.
From Adam Balkcom, Atlanta, Georgia
I am a personal trainer devoted to bringing my clients into optimum fitness and nutrition.
Something I have been hearing a lot lately is that microwaving kills a lot of the nutrients in the food. I now cook everything in a toaster oven. Is this overkill?
My clients and I appreciate you helping us clear up confusion over getting the most from the foods we eat.
Adam, Thank you for your question and for working to bring better nutrition and fitness to your clients.
The truth is that, no matter how food is cooked, whether it’s steamed, boiled, microwaved, or – in your case– cooked in your toaster oven, any type of cooking will destroy some nutrients in foods. The key, according to the U.S. Department of agriculture, is to prevent excessive losses of vitamins and minerals by using proper preparation and cooking techniques.
Microwave ovens cook food using oscillating electromagnetic waves, much like radio waves. The energy penetrates your food and excites the water and fat molecules, creating energy in the form of heat. The heat is fairly evenly distributed in the food cooking it quickly and evenly, as opposed to boiling, baking or steaming, which heat foods from the outside until they are cooked inside. Because microwave cooking is generally faster, fewer vitamins will be destroyed in the cooking process.
Water, heat, air, and light can be the enemies of nutrients in foods. They can also be diminished if food is cooked in water that’s too acidic or is too alkaline.
Foods can contain both fat-soluble vitamins, which include vitamins A, D, E, and K, and water-soluble vitamins, which include vitamin C and the B vitamins. Water-soluble vitamins are less stable and can be destroyed by water, heat, air and light.
The USDA advises that the key to avoid losing nutrients is by carefully handling and preparing foods.
*Water: Avoid soaking foods in water, which dissolves water soluble vitamins and minerals. Use as little water as possible when boiling, and incorporate the vitamin-rich water into other dishes such as soups and sauces. Steaming is preferable to boiling. Some foods, such as rice, pasta and beans, are coated with vitamins and minerals, so soaking or rinsing will diminish nutrients and should be avoided.
*Heat: Overcooking, high temperatures, or prolonged cooking are enemies to nutrients, especially vitamin C.
*Light: Allowing foods to stand in open light for prolonged periods can destroy some vitamins. Milk, for example, which is a good source of the B vitamin riboflavin, will lose much of that vitamin when left exposed to light. Light obstructing cardboard containers can help prevent this vitamin loss.
*Air: Exposure to air destroys vitamins A, C, E, K, and the B vitamins. To reduce vitamin loss cut and cook vegetables in big chunks so that less surface area is exposed to the air. Cook vegetables soon after cutting until just tender. Even better is to serve raw vegetables and fruits whenever possible.
*pH Balance: Do not add baking soda to vegetables when cooking because it makes the water alkaline and destroys thiamin and vitamin C.
The bottom line, Adam, is that your toaster oven may be overkill. Microwave cooking exposes most foods to less heat, water, and for shorter cooking periods, so that means that fewer vitamins will be destroyed during cooking. If time is a factor, microwaving is much quicker too
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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.