Q: Do microwaves alter food at the molecular level, and does this make the food unsafe to eat?
A: Judith C. Thalheimer, RD, LDN, executive editor of Tufts Health & Nutrition Letter, answers: “Microwave ovens bombard food with electromagnetic waves. This makes water molecules inside the food vibrate, which produces heat and cooks the food from the inside out. This may sound concerning, but it is safe. Whereas ionizing radiation (the type of radiation used in x-rays) affects atoms in living things and can damage the DNA in genes, potentially leading to cancer-causing mutations, electromagnetic waves, otherwise referred to as electromagnetic radiation, is non-ionizing. In addition to microwaves, non-ionizing radiation is around us every day in the form of light and radio waves.
As for the first part of your question, microwaves do change food at the molecular level by heating it, but so does every other method of cooking food. Heat causes proteins to change shape (denature). It can also degrade some vitamins, primarily vitamin C. Microwave ovens tend to preserve the nutrients in food better than other cooking methods because they heat food quickly, and shorter heating time means less time for nutrients to break down.
The most important thing to keep in mind when using a microwave oven is safety. Handle hot items with care, and make sure meats are fully cooked. Microwave ovens are more likely to leave cold spots in food than other cooking methods, so it is important to use a food thermometer to check the temperature of microwaved meat products in several spots to ensure there are no raw areas that could transmit foodborne microbes. For mixed dishes, it is a good idea to stir midway through the heating cycle, especially when reheating.
When used correctly, microwaves are generally an efficient and safe way of reheating and cooking food, and minimally alter food at the molecular level.”
Richard D. Siegel, MD, is the co-director of the Diabetes and Lipid Center and a doctor at the Weight and Wellness Center at Tufts Medical Center.