Five-a-day keeps the doctor at bay

But what constitutes a portion of fruit or veg? And how do we maximise their benefits? Alice Lascelles finds out

Are you getting your greens? According to the Department of Health (DoH) – probably not. Most of us are only managing around half the recommended five portions of fruit or vegetables a day that we need for a healthy diet. Despite strong evidence that the five-a-day plan can reduce the risk of heart disease and some cancers by up to 20 per cent, the UK continues to have one of the lowest fruit and vegetable intakes in Europe.

Last week the Government announced a revamped food-labelling scheme designed to help consumers achieve the target. Labels will now indicate how many portions of fruit or vegetables are present in certain products.

The changes may lead food manufacturers to review their recipes to decide whether they would meet the nutritional tests demanded by the Department of Health. Heinz has come under fire for labelling small tins of spaghetti and sausages in tomato sauce as containing "one portion of fruit or vegetables". Critics point out that any health advantages risk being outweighed by the high levels of sugar and salt in the product.

Under the new system, products will have to meet stringent health standards to carry the trademarked five-a-day logo. But companies will still be free to run their own unregulated schemes, so what do we need to know?

Part of the problem has been consumer confusion over what a "portion" is. The DoH defines a portion as "a typical serving or a decent-sized helping" of fruit or vegetables – so a banana, a serving of peas or a handful of grapes would all count.

Juice, however, counts as only one portion however many glasses you drink. According to the DoH there are two reasons for this. Unlike whole fruit, juice lacks fibre, which aids the uptake of nutrients and helps to prevent bowel cancer. The juicing process is also responsible for converting fruit sugars into a different form more harmful to teeth. Beans and pulses belong to another group that only counts once, while potatoes, which are considered a starch, don't count at all.

If you want to maximise the benefits of your diet, research suggests it's also worth paying attention to the way you prepare and store your food.

While it was previously believed that cooking reduced the health benefits of some vegetables, a study by the Institute of Food Research in Norwich suggests just the opposite. Scientists found that when carrots, broccoli and spinach were cooked and mashed, the human body was able to absorb up to five times more carotenoids, a group of cancer-fighting chemicals, than when the vegetables were eaten raw. Cooked, rather than raw, tomatoes also provide a much higher level of a carotenoid called lycopene, which is important for combating cancer and heart disease.

The DoH, however, warns that while cooking raises levels of some nutrients, it can lower the levels of others – vitamins C and B in particular – so the secret is to eat a good balance of raw and cooked.

Storage can also affect the nutritional value of fruit and vegetables. The British Nutrition Foundation (BNF) recommends replenishing your stocks regularly, rather than buying in bulk once a week.

"Vitamin content can decrease over time," says a BNF spokesperson. "If you leave food sitting at the back of the fridge for a week, it will end up having a lower nutritional value. If possible you should try and buy fresh produce every couple of days." If you can't, the BNF says frozen vegetables can offer a good alternative, as the freezing process stops the deterioration of vitamins.

Preparation also matters: "If you're buying vegetables that are pre-cut, like a ready-prepared stir fry, they're likely to contain less vitamins than something you prepared yourself."

This advice is probably not what the more time-starved among us want to hear. Ian Marber, a nutritionist and founder of The Food Doctor clinics, says lack of time is a common excuse for failing to eat healthily: "People say that they don't have time to prepare food – but what's faster than an apple or a banana?"

If you're still struggling to get your five-a-day then supplements can seem an easy alternative. But Marber says this tends to be the response of the "worried well", who self-prescribe supplements they don't really need.

Experts are unanimous that the best way to get your nutrients is from your diet. But some remain pessimistic about our ability to change: "It's sensible because it's an achievable target," says Marber. "I just don't know how many people will even try to reach it."