For the record, I haven't used the microwave at all in years. These are a few paragraphs taken from a much longer article at: http://www.mercola.com/article/microwave/hazards.htm
(See another link for a different article at the bottom of the page)
Artificially produced microwaves, including those in ovens, are produced from alternating current and force a billion or more polarity reversals per second in every food molecule they hit.
Production of unnatural molecules is inevitable. Naturally occurring amino acids have been observed to undergo isomeric changes (changes in shape morphing) as well as transformation into toxic forms, under the impact of microwaves produced in ovens.
One short-term study found significant and disturbing changes in the blood of individuals consuming microwaved milk and vegetables. Eight volunteers ate various combinations of the same foods cooked different ways.
All foods that were processed through the microwave ovens caused changes in the blood of the volunteers. Hemoglobin levels decreased and over all white cell levels and cholesterol levels increased. Lymphocytes decreased.
Dr. Hertel was the first scientist to conceive and carry out a quality clinical study on the effects microwaved nutrients have on the blood and physiology of the human body.
His small but well controlled study showed the degenerative force produced in microwave ovens and the food processed in them. The scientific conclusion showed that microwave cooking changed the nutrients in the food; and, changes took place in the participants' blood that could cause deterioration in the human system.
"Leukocytosis, which cannot be accounted for by normal daily deviations, is taken very seriously by hemotologists. Leukocytes are often signs of pathogenic effects on the living system, such as poisoning and cell damage.
The increase of leukocytes with the microwaved foods were more pronounced than with all the other variants. It appears that these marked increases were caused entirely by ingesting the microwaved substances.
Another article, called "The Proven Dangers of Microwaves" taken from Nexus Magazine
http://www.mercola.com/article/microwave/hazards2.htm
Do You Microwave Your Food? You’re Zapping Away Nutrients and Risking Your Health