SARAH-DESIREE TIEMANN

This week: Smoothies versus Fruit Everyone knows fruit is good for you. It gives you vitamins and minerals, contributes much of our essential dietary fibre and contains important antioxidants, helping to prevent diseases.

But there is a difference between the liquid version, in the form of a juice or smoothie, and the whole fruit.

What's the difference between a juice and a smoothie? Smoothies are the whole fruit, blended, while juice is the liquid extracted from the fruit. Because juicing removes the skin and the fruit pulp, it loses some nutrients such as carotenoids and flavonoids. Still, both drinks can be highly beneficial.

How do they benefit you? According to research at the University of Montpellier, fruit juices are more powerful in helping to prevent atherosclerosis (the build-up of fatty plaque deposits in the arteries leading to heart attacks) than the fruit itself. The action of juicing supposedly increases the amount of antioxidants - phenols - that are strongly associated with benefiting heart health. The team fed hamsters a high fat diet and then divided them into groups. Some were given whole apples or grapes, some the juice of those fruits, and some water. Purple grape juice, which had the highest phenol content, had the strongest effect in lowering cholesterol levels and reducing fat accumulation, followed by whole grapes, then apple juice and apples. But before you start downing only juices and smoothies, The British Dental Health Foundation warns of tooth damage due to smoothies. Juice is acidic and has a corrosive effect on the tooth enamel. Dr Nigel Carter, chief executive of the BDHF, said: "Fruit smoothies are becoming increasingly popular and the fruit content can make them seem like a good idea. However, they contain very high levels of sugar and acid and so can do a lot of damage to the teeth." .

Are they OK for everyone? Doctors tend to discourage people who have diabetes from drinking lots of juice. According to the Food Standards Agency: "Fruit juice is high in fructose (fruit sugar) so it can cause blood sugar levels to rise quickly. It's best for people with diabetes to drink juice with a meal and avoid having more than one small glass a day."

Then should we stick to whole fruit? No, not at all: fruit served in whatever way is good for our health. Probably the best way to consume fruit is in varied forms - as dried fruit, juices and smoothies and as whole fresh fruit.

So how much should we have? The guidelines are five portions of fresh fruit and veg a day, but many nutritionists stress that this should be the bare minimum. Here are some Food Standards Agency pointers on what constitutes a portion: one apple, banana, orange or other similar sized fruit ; two plums or similar sized fruit ; half a grapefruit or avocado; one slice of large fruit, such as melon or pineapple; three heaped tablespoons of vegetables (raw, cooked, frozen or tinned); three heaped tablespoons of beans and pulses (however much you eat, beans and pulses count as one portion); three heaped tablespoons of fruit salad (fresh or tinned in fruit juice) or stewed fruit; one heaped tablespoon of dried fruit; one handful of grapes, cherries or berries; a dessert bowl of salad; a glass (150ml) of fruit juice (however much you drink, fruit juice counts as one portion).