We all know we should be having our 5 a day and filling our plates with colourful fresh produce, but do you really know how much we should be eating?

A new study has shown that most adults are still unsure about the portion sizes of fruit and vegetables they should be eating. Even with an extensive 5-day campaign in 2003 in the UK to educate what constitutes our 5 a day, according to HSIS, 86 per cent of people are still uncertain.

The researchers based their investigation on the government’s National Diet and Nutrition Survey and the Defra Family Food findings.

They discovered that 16 years after the launch of the five-a-day campaign, only 31 per cent of adults aged between 19 and 64 are consuming their five a day.

Just over a quarter of adults aged 65 and over are reaching the goal, while only eight per cent of 11 to 18-year-olds are doing the same.

Dr Emma Derbyshire, a public health nutritionist and author of the study, said the findings are a “real cause for concern”.

“Low intake of all these nutrients damages brain function and increases the risk for heart disease, bone disease and premature death,” Dr Derbyshire said.

“At the moment the message is still not getting through,” she added.

An adult portion of fruit or vegetable should be approx. 80g. That is the equivalent of 2 kiwi fruits, 1 apple or pear or a slice of melon. For vegetables that is 2 broccoli spears, 3 tablespoons cooked veg such as carrot, peas, or sweetcorn or 1 medium tomato.