Microwave ovens can be a safe and effective way of heating food if correctly used and kept in good condition.
The safety of microwave ovens
Successful microwave cooking depends on understanding the limitations as well as the benefits of this type of cooking.
14 August 2009 | Updated 14 October 2011
Microwave cooking and nutrition
The majority of reports published on the nutritive value of foods cooked in microwave ovens indicate that food prepared in this manner is at least as nutritious as comparable food cooked by conventional methods.
Most of these studies have concentrated on vitamin retention and indicate that cooking in minimal water for a reduced time, as occurs with microwaving, promotes the retention of the water-soluble vitamins particularly of vitamin C and thiamin.
Microwave cooking is preferable to boiling to minimise the leaching of vitamins into the cooking water; in this regard it is similar to steaming. For the same reasons given for vitamin C, microwave cooking enhances mineral retention in vegetables.
Studies have not revealed any non-heat related effects on the macronutrients of foods, proteins, fats and carbohydrates, when cooked in microwave ovens. There may be slight differences in denaturation rates of proteins when food is heated in a microwave oven compared with conventional heating but this is due to differences in the time and temperature to which the food is subjected.
Microwave cooking enhances mineral retention in vegetables if cooked in minimal water for a reduced time.
Recent reports reveal that cooking vegetables in a microwave oven leads to a greater loss of soluble phenolic antioxidant compounds than does conventional cooking.
However, this appears to have been at least partly due to the use of more cooking water than is necessary with microwaves. The role of these phenolic compounds in human nutrition remains an open question.
Far less information is currently available on the effect of microwave cooking on other food components such as carbohydrates, lipids and fat-soluble vitamins. The quality of protein is higher in microwaved than in conventionally cooked food as far less oxidation occurs in meat cooked in a microwave.
Lack of browning is visible evidence that heating is gentler, and makes it likely that vitamins A and E are better retained than in conventional cooking. However, these differences are likely to be slight and of little nutritional significance.
Reheating food quickly in a microwave retains more nutrients than holding food hot for long periods; this is significant in institutions and hospitals where food may be held hot for several hours in traditional catering systems.
The nutritional value of food does not depend only on the way in which it is cooked. Just as important are shopping wisely for quality products, correct temperature control during storage and preparation and serving food promptly after it is prepared.
Leaching effects aside, there seems to be little difference to the retention of nutrients between food cooked by microwaves or by conventional means, provided that cooking time and temperature guidelines are carefully followed.