Boil, steam or fry: are we getting the best from our vegetables?

The message that we need to consume our 5-a-day (about 800g of fruit and vegetables in total) is one that appears to be making a positive impact on people’s food choices. By eating fruits and vegetables that are of a variety of different colours, you can get the best all-around health benefits. Fruit and vegetables are termed ‘whole foods’, and are rich in a large amount of nutrients, such as vitamins, minerals, fibre and phytochemicals. Tomatoes for example are extremely rich in lycopene, a phytochemical that is suggested to reduce risk of cancer by activating special cancer preventive enzymes called phase II detoxification enzymes, which remove harmful carcinogens from cells and the body. When it comes to children, we all know how fussy they can be, and it’s often useful to offer them small amounts of different coloured types that can be less overwhelming than one large portion of dreaded broccoli.

Whilst many types of fruit and vegetable can be eaten as they are, many can’t, and many of us choose not to consume them in their raw state. But what is the effect of different cooking methods on their macronutrient and antioxidant capacity?

Microwave cooking has gained considerable importance as an energy-saving, convenient, and time-saving cooking method. However, the effects on our food remain controversial. Whilst the effects of microwave cooking on nutritive values of moisture, protein, carbohydrate, lipid, minerals, and vitamins appear minimal, it is the actual changes in the molecular structure of nutrients that still seem unclear and as a consequence many people choose to avoid or certainly limit its use.

Generally, water is not the cook’s best friend when it comes to preparing vegetables. Many of the vitamins and minerals within vegetables and fruit are water soluble, and therefore any cooking process that involves contact with water will deplete levels of nutrients to different extents (boiling is the worst, whilst steaming is much more nutrient friendly). Stir frying on the other hand, usually involves the use of some kind of culinary oil into which water soluble nutrients are unable to enter. Not only does stir frying help retain nutrient levels, but also the resulting texture and colour can be more appetising than other cooking methods (and it’s quick!).

Overall, there will always be a loss in nutritional value of foods, however, the degree of vitamin and mineral losses from food is influenced by various factors, for example the type of food, variety of food, the way of cutting, preparation, duration and method of cooking.