Carrie Ruxton PhD, Registered Dietitian

The beneficial effects of fruits and vegetables to our health are beyond doubt. Interest in fruits and vegetables arose when researchers noticed that Mediterranean people experienced less heart disease and cancer. The Mediterranean diet, compared with the UK diet, is characterised by a higher intake, of fruits, vegetables, oily fish, olive oil (containing monounsaturated fatty acids) and red wine. Even within the UK, people with a higher consumption of fruits and vegetables appear to have a lower risk of heart disease and cancer. So what is it about fruit and vegetables that reduces the risk of heart disease and cancer, and how much fruit and vegetables should we be eating to obtain the maximum health benefits?

Mechanisms for action

It is not easy to explain why fruits and vegetables should protect against heart disease and cancer. When researching the effects of diet in humans it is rarely possible to separate out the impact of individual foods. Also, with Western diets containing plant components from more than 40 different botanical families, identifying the key active ingredients in fruits and vegetables is extremely difficult.

Initially, it was believed that antioxidants explained the beneficial effects of fruits and vegetables. These important nutrients can counteract damage caused by free radicals thus inhibiting the development of fatty streaks in coronary arteries. Certainly, people at high risk of heart disease have been found to have lower levels of antioxidants in their blood than people with better heart health. Yet, when large-scale studies of synthetic antioxidant supplements were carried out, no clear beneficial effects were found. This suggests that the benefits of fruits and vegetables could be due to many nutrients working together, rather than just one or two.

So, what other nutrients are in fruits and vegetables? Researchers have found a host of other active components including flavonoids, lycopene, potassium, magnesium, selenium, folate, organosulphur compounds and fibre. Flavonoids are thought to reduce heart disease risk by inhibiting the development of fatty streaks, reducing the formation of clots, and improving the ability of blood vessels to dilate, which prevents blockages. The main sources of flavonoids in the diet are onions, citrus fruits, apples, cabbage and broccoli. Folate, found in spinach, asparagus and cabbage, may be important because it is thought to reduce levels of homocysteine in the blood, an amino acid linked to heart disease. Lycopene is a key component of tomatoes (both fresh and processed) and is believed to be a powerful antioxidant and a cancer growth inhibitor. Fibre can be divided into two types, soluble and insoluble. Scientists think that both types impact on those factors that influence the risk of chronic disease. Again, the evidence suggests that a food-based approach – providing a variety of fibre from fruits, vegetables and wholegrains – is superior to bran-based supplements.

How much are we eating?

The National Diet and Nutrition Survey (NDNS) provides regular information on the nation’s diet. A recent survey found that most people in the UK don’t eat 5 portions of fruit and vegetables per day. Instead, average intakes were around two portions with teenagers, young men, people from lower income groups, smokers and single /divorced people having the lowest intakes. People living in the South East of England ate more fruit and vegetables than people from Wales, Scotland and the North of England. Unsurprisingly, health in the South East is better!

How much is enough?

The scientific evidence shows that the impact of fruit and vegetables is ‘dose-dependent’. This means that the protective effects increase with every extra portion eaten, with the maximum health benefits seen around 4 to 8 portions a day. This fits well with the UK Government’s recommendation of 5 portions a day, backed up by the ‘5-a-day’ national campaign. Different colours of fruits and vegetables contain different profiles of nutrients so it’s important to vary what you eat. Try to choose something from each colour in the fruit and vegetable spectrum; namely green, purple, red, yellow/orange and white. Examples include broccoli, beetroot, red cabbage, squash and cauliflower. Selecting seasonal fruit and vegetables are a good way of ringing the changes and eating more variety. Markets and farm shops offer great bargains and usually sell local produce, representing fewer food miles.

Table 1 gives examples of what represents ‘one portion’. Fresh, frozen, dried and tinned fruits and vegetables all have a place in the diet. Fruit juices and smoothies count as one portion, no matter how much is drunk.

Table 1: Examples of 1 portion of fruit or vegetables

More details can be found on www.dh.gov.uk/PolicyAndGuidance

Make 5-a-day easy

Eating 5-a-day is easier than you think. Include 1 or 2 portions with meals and a portion as a snack and you have reached your goal! Some ideas are given below.

At breakfast:

• Add sultanas, dried apricots, grapes or sliced fresh fruit to your cereal
• Drink a glass of fruit juice or a fruit smoothie
• Have grilled tomatoes and mushrooms on toast

For lunch:

• Have a bowl of vegetable soup
• Add vegetables, fruit or salad to your sandwich e.g. tomatoes, peppers, apple or red onion
• Eat a tasty pasta or cous cous salad with plenty of avocado, sweetcorn, apple or chick peas
• Try hummus with pitta and crunchy raw vegetables e.g. carrots, celery, peppers or cauliflower florets

At dinner:

• Add mushrooms, peas or carrots to your mince, stew, Shepherd’s pie, curry, chilli or bolognaise sauce.
• Include plenty of vegetables when making a stir fry, risotto or pasta sauce, e.g. courgette, sweetcorn or asparagus
• Serve at least two portions of vegetables with meat, chicken or fish, e.g. broccoli, swede, carrots, cabbage, turnip or green beans
• Try unusual vegetables such as beetroot, pumpkin, fennel or butternut squash. All are delicious when roasted
• Mix fresh fruit salad, tinned fruit or baked fruit with yoghurt or ice cream

Snacks:

• Have a piece of fresh fruit when on the go
• Keep dried fruit with you for when you get hungry
• Choose snack packs of baby carrots or make your own carrot batons