found this at ask.com, which points to research at the
Division of Nutritional Sciences, Cornell University:

does microwave cooking effect the chemistry of a food --
nutritional value, creation of antigenic, or carcinogenic,
compounds, ..?


As with any cooking method, microwave cooking will
effect food somewhat. It has been found, however, that
nutritional value (vitamins, etc.) are preserved in vegetables, etc.
vs. other cooking methods. Dr. Gertrude Armbruster of Cornell
University
did a study which varifies this. Meats cooked on the grill and
conventionally (the old charred roast, bacon, etc.) show signs of
carcinogenic properties whereas meats in the microwave do not.
U.S.A. Today ran a front page article regarding microwaved meat
being the healthiest on March 27, 1991.
More fat is removed during microwave cooking than other
methods which make it more heart healthy also.

Philip Thrift
http://www.paleofitness.com