Shoppers are entirely unaware that purple foods are as healthy as greens, according to a new survey.

A study by the Blackcurrant Foundation found that 53% identified 'green' foods as being beneficial to health. Some 24% named 'red' foods but only 14% suggested 'purple'.

Blackcurrants contain high levels of vitamin C and anthocyanins that protect against conditions including joint inflammation, kidney stones and cardiovascular disease.

Only 8% of respondents actively seek out purple foods as part of their daily diet to stay healthy, compared with 50% for greens. Some 60% of shoppers said it never occurred to them to link food colour with health benefits.

"It is imperative that we eat a rainbow of colours in our daily diet to ensure that we are incorporating the most beneficial food components to keep us healthy," said nutritionist Juliette Kellow.