Q: Are there health risks associated with eating food cooked in microwave ovens? A friend told me that she has read a magazine article that says food cooked in microwave ovens cause cancer. What is the difference between microwave cooking and the way we usually cook food?
    --Lina E, Makati City

A: Microwave cooking differs from conventional cooking where the latter applies heat on the external surface of food. Microwave cooking, on the other hand, are used to produce the heat necessary to cook food.

Microwaves like light waves or radio waves are a form of electromagnetic energy.  They consist of very short waves that travel through space at the speed of light. Inside a microwave oven, they are generated by an electron tube called a magnetron. Microwaves pass through glass, paper and plastic but they are absorbed by food. When absorbed by food, they cause water molecules in the food to vibrate, which results in the production of heat.

Although heat is produced directly in the food, microwave ovens do not really cook food from the “inside out.” It is only the outer layers that are heated and cooked primarily by microwaves. The inside is cooked mainly by the conduction of heat from the hot outer layers.

Microwave cooking is a relatively recent (1980s) phenomenon. Based on available evidence to date, the US Food and Drug Administration (FDA) maintains that current microwaving usage is not harmful. But anti-microwave oven advocates cite studies that show that:

• Microwaving baby formulas converted certain trans-amino acids into their synthetic cis-isomers, which decreases the milk’s nutritional value.

• Microwaving prepared meats sufficiently to insure sanitary ingestion caused formation of d-Nitrosodienthanolamines, a well-known carcinogen.

• Microwaving milk and cereal grains converted some of their amino acids into carcinogens.

• Thawing frozen fruits using microwaves converted their glucoside and galactoside containing fractions into carcinogenic substances.

• Extremely short exposure to microwaves of raw, cooked or frozen vegetables converted their plant alkaloids into carcinogens.

• Carcinogenic free radicals were formed in microwaved plants, especially root vegetables.

• Microwaving creates new compounds, called radiolytic compounds, which are unknown fusions not found in nature.

Of course, we do not know if the carcinogens generated by microwaving food are any more than the carcinogens generated by traditional ways of cooking food. In fact, microwave oven advocates insist that microwaved and irradiated foods do not have any significantly higher radiolytic compounds than do broiled, baked or other conventionally cooked foods. 

Microwave ovens offer a lot of conveniences. They cook and reheat faster and are cost efficient on electricity. They do not require pre-heating and can be used immediately upon switching on. They do not heat up the kitchen area. Also, microwave cooking means a less messy and odorous kitchen. Nevertheless, until such a time we have hard and fast evidence to show that microwave cooked food has no health risk, it is perhaps best that microwave ovens are used judiciously.

Many dietitians recommend microwave ovens only for heating, browning and caramelization. That’s certainly a suggestion worth considering.

(E-mail inquiries on health matters to: medical_notes@yahoo.com or wellbeing@mb.com.ph.)