There are many advantages to eating fruit and vegetables raw. Water-soluble vitamins (such as vitamin C) are destroyed by heating, so there will be less vitamin C in a cooked carrot than in a similar raw carrot.

But for some nutrients, cooking (and juicing) is more nutritious, because it makes the nutrients more easily assimilated. Cooking and juicing breaks down tough fibres and allows the digestive juices to work more effectively on the vegetable. This is particularly important for someone who is elderly, ill or who has impaired digestion.

For example, research has shown that we absorb approximately 3-4% of carotenoids from raw carrots and 15-20% from cooked carrots. Carotenoids are plant pigments that give yellow, orange and red fruit and vegetables their colour. Carotenoids are powerful antioxidants, so have a role in helping us fight old age and cancer.

Juicing fruit and vegetables is an excellent way to combine the advantages of both raw and cooked. There are a lot of different juicers out there, so I decided to ask the experts at the Wholistic Research Company in the UK for more about juicing and juicers.

What are the benefits of a juicer over just eating fresh fruit and vegetables?

The use of fresh fruit and vegetable juices in both normal and therapeutic diets has long been established as a great aid to natural health, energy and well-being. The high mineral and nutrient content, combined with the vibrant life-energy of fresh fruits and vegetables, makes pure, fresh juice a wonderful part of a healthy person's diet. In no other way can one consume the nutritional content of, for example, a pound or two of apples and carrots (in a glass) and then go on to eat a healthy breakfast. Fresh juices are an invaluable supplement to any person's diet. Indeed there are therapies that rely almost entirely on the power and nutrition available in juices to rid an ailing body of serious illness, even cancer. The body is stimulated by such concentrated goodness to throw off negative, pathological cellular deterioration and regain excellent health.

What are the advantages of a juicer over bought juice?

Making fresh juices from your own juicer provides you with the same live enzymes that are available in raw fresh fruit and vegetables. These fresh raw foods give us more energy and sparkle than cooked, 'dead' foods, and 'dead' juices that have been sitting in a container on the supermarket shelf for days, weeks or even months. This energy (from the freshly made juice) is concentrated, and you feel it as soon as you drink it. It can clear your head and make you feel light and energetic.

Juicers can vary dramatically in price, so what should you look for in buying a juicer?

In order to extract juice from fruits and vegetables, it is necessary first to break down the cell walls and fibres and then separate out the juice. Ideally, a top quality juicer should deliver a nutrient-rich juice on the one hand and a dry pulp of cell walls and fibres, on the other. There are basically two types of juicers: centrifugal juicers and masticating juicers.

So what is a centrifugal juicer?

This is an inexpensive juicer and is widely available. It merely grates fruits and vegetables, leaving strings of unbroken cells. The juice from the cells that have been broken is then spun out at very high speed (6,000 to 10,000 rpm). Because the juice is flung out, it mixes with the air and so oxidises (turns brown) quickly. The pulp usually remains very moist, because the process has not extracted all the juice. Not only is this more wasteful, but the juice is paler, more watery, lower in nutrient value and often quite insipid in flavour.

That doesnt sound very appetising. Are masticating juicers any better? Masticating juicers provide richer, more flavourful, nutritious juices. They are altogether more serious, although more expensive, but should be considered to be an investment in good health. They more thoroughly break up fruit or vegetables, and press out the juice from the resulting pulp inside a nose cone with a narrow opening.

This is far more efficient than centrifugal action. A good masticating juicer will extract up to five times more nutrients than centrifugal juicers.

Masticating juicers - like the popular American champion juicer - use a rugged cutter, spinning at 1425 rpm. This will juice whole carrots and quartered apples speedily and with ease.

There are also slower masticating juicers that use a single auger or twin gears, revolving at 80 to 160 rpm, to more gently crush smaller pieces of fruit and vegetables. They are especially useful for juicing tough fibrous greens and wheatgrass (a powerful healing natural tonic).

You can also juice wheatgrass with a manual masticating juicer. A good one can be relatively inexpensive to buy, and is similar to an old fashioned table-mounted mincer that is turned with a handle. Many masticating juicers will also make smoothies, purees, nut butters, pasta, baby foods and frozen fruit ice creams.

The price of a good juicer may seem quite high, but the quality of the juice produced, and the long life of the juicer, far outweigh the initial outlay when compared to the cheaper, far less efficient models on the market.