Can microwaves nuke the nutritonal value out of our food?

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The success of The Darkness and the return of Starsky and Hutch and the Chopper bike have made me quite nostalgic for the seventies. Mind you, not everything about this era was good. These were the days, after all, when a glass of fruit juice or half a grapefruit might be found as starter options in restaurants, and the presence of the black forest gateaux loomed large. Another portion of seventies cuisine best forgotten was a general tendency for vegetables to be cooked to within an inch of their lives. Such culinary excesses not only may result in a rather unappetising mulch, but can also rob vegetables of much of their rich stash of health-giving goodies. Many find the more recent vogue for al dente cooking to be more pleasing to the palate, and can be satisfied in that it may well help preserve a vegetable’s nutritional bite too.

Recognition of the fact that contracted cooking times mean extended benefits from the food we eat have led some to extol the rapid-fire food preparation offered by microwave ovens. Recently, this concept was subjected to a degree of scientific scrutiny. In a study published in the Journal of the Science of Food and Agriculture, researchers assessed the effects of a variety of cooking methods on nutrient levels in broccoli. While boiled broccoli was found to lose two-thirds of its original content of disease-protective nutrients known as flavonoids, this actually compared quite favourably with the whopping 97 per cent loss induced by microwave cooking. Analysis of other nutrients revealed similarly dire depreciations. Contrary to what may be expected, it seems we can microwave goodbye to a good deal of the nutritional goodness vegetables have to offer.

While this study suggests that boiling may indeed be preferable to microwave cooking, other research shows that how vegetables are boiled may also effect their nutrient status. One study found, for instance, that frozen vegetables such as spinach, peas and green beans retain appreciably more vitamin C when plunged into hot water direct from the freezer, than when thawed prior to cooking. The amount of water in which vegetables are placed also seems to have an important bearing on their nutritional status. A study published last year discovered that the smaller the volume of water used to boil vegetables, the better their retention of important nutrients known as phenolics. The evidence suggests that the one way to preserve the nutritional value of boiled vegetables is to ensure they don’t end up in deep water.

There is some evidence that there are even more benefits to be had by going off the boil and opting for steaming instead. For instance, in the study which identified hefty flavonoid losses from the microwaving and boiling of broccoli, steaming induced only an 11 per cent degradation in this type of nutrient. In another study, boiling was found to reduce the level of folate (believed to protect against both heart disease and cancer) in spinach and broccoli by more than half. In comparison, steaming had minimal effects on the level of this vitamin. For those looking to get maximum nutritional value from their cooked vegetables, I reckon it’s full steam ahead.

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