Sainsbury's stocks a range of Italian antipasti that includes artichokes, mushrooms and peppers preserved in oil. Would a serving of any or all of them count towards my five a day? And how large is a serving?

Yes, the antipasti vegetables do count if you have about 80g of them in total. In practice this will be approximately three tablespoons worth once they have been drained of all the oil.

The aim is to try to eat “five portions a day” of fruit and vegetables in total. Both frozen and canned versions also count and are a convenient way to top up fresh versions. The idea is that you get as wide a variety as possible for a good range of vitamins, minerals and various supernutrients.

The advice to eat “five a day” is based on work by the World Health Organisation, which in the early 1990s concluded from worldwide scientific studies that people who ate 400g of vegetables and fruit daily appeared to have lower incidences of health issues from heart disease to certain cancers.

The WHO decided that an average serving of fruit and vegetables hovers around the 80g mark. Since 400 divided by 80 is five, this is where the guidance to eat “five a day” comes from, preferably in a three-vegetable and two-fruit split.

It is worth pointing out that 400g a day is the minimum target that we should be trying to hit. Given that we actually eat only three a day on average in the UK at the moment, the chances of most of us getting more is probably a bit ambitious.

With the credit crunch affecting almost everyone's purse now, the good news is that you do not need to break the bank to reach the target by relying on exotic imports. Home-grown apples, pears and plums along with beetroot, courgettes, radish and broccoli are all in season now and are packed with nutrients and supernutrients.

As well as taking advantage of seasonal produce, frozen vegetables such as peas offer really good value. If you get them back to your freezer from the shops pretty rapidly, store them at less than minus 19C (the correct temperature for a home freezer) and cook them according to pack instructions, they will have more vitamin C and certain B vitamins than fresh peas that have been harvested, transported to stores and been around several days before they are cooked and eaten once home. This is likely to hold true for frozen beans and broccoli as well.

Canned vegetables can also score well on the nutritional front. For example, the canning process actually makes it easier for us to absorb the orange betacarotene pigment in carrots (thought to play a role in protecting our skin from sun damage), and the red pigment lycopene in tomatoes, good intakes of which have been linked positively to prostate and heart health.

When opting for canned vegetables, it is preferable to go for those canned in water rather than salted water and to choose fruits in fruit juice rather than syrup. Equally, vegetables in your antipasti will, like canned vegetables, still provide you with plenty of carotenes - in your peppers, for instance - if you are watching your weight it is best not to go overboard, given that they come in oil.

Know your portions

80g is a normal-sized apple, orange, pear, peach or banana; two small fruits such as satsumas, plums and apricots; one slice of melon, pineapple or papaya; two slices of mango; or a tablespoon of dried fruit.

A portion is also three heaped tablespoons of vegetables such as courgettes, carrots and peas; or four heaped tablespoons of greens such as cabbage. A vegetable-packed soup, stew or casserole, or a pizza with lots of tomatoes, onion and mushrooms on top, all count as about one serving.

Botanically a vegetable, potatoes are classified as a carbohydrate and do not count towards your five a day. Nor do herbs, even though they are packed with supernutrients and vitamins.

A 150ml glass (the size of a small yoghurt pot) of any fruit or vegetable juice or smoothie counts as one serving. More does not count as two. Dentists warn that too many of these drinks can cause tooth erosion.

If you have any nutrition questions for Amanda, e-mail her at amandaursell@thetimes.co.uk