Although a small study by Hans Hertel in Switzerland over 10 years ago suggested increased cholesterol levels, decreased haemoglobin, decreased red cell counts and leukocytosis in people eating microwaved foods, no study has corroborated these findings since. Another uncorroborated study showed a decrease in IgA and liposome levels in microwaved milk.
In general, the quality of nutrients and their quantity depends on time, temperature and available water. Time and water required are less in microwave cooking compared to pressure cooking and conventional cooking, thereby giving this method of preparation a clear edge. This is what is widely accepted today. Higher temperatures although theoretically can alter cell membranes have not been shown to do so in vitro.
The role of microwaving in altering the chemical nature of the dish used is currently under study. Results are not expected soon. The consensus favors microwave cooking currently and there is no consistent evidence to the contrary.