Happiness and mental health are highest among people who eat seven portions of fruit and vegetables a day, according to a new report.

Economists and public health researchers from the Univ. of Warwick studied the eating habits of 80,000 people in Britain. They found mental wellbeing appeared to rise with the number of daily portions of fruit and vegetables people consumed. Wellbeing peaked at seven portions a day.

The research was carried out in conjunction with Dartmouth and is due to be published in the journal Social Indicators Research.

Most western governments currently recommend “5 a day” for cardiovascular health and as protection against cancer risk.

In Britain today, a quarter of the population eat just one portion or no portions of fruit and vegetables per day. Only a tenth of the British population currently consume the magic number of seven or more daily portions. The study does not distinguish among different kinds of fruits and vegetables and it defines a portion as approximately 80 grams.

Study co-author Prof. Sarah Stewart-Brown says, “The statistical power of fruit and vegetables was a surprise. Diet has traditionally been ignored by well-being researchers.”

She emphasizes that much remained to be learned about cause-and-effect and about the possible mechanisms at work, and that randomized trials should now be considered.

Fellow co-author, economist Prof. Andrew Oswald from the Centre for Competitive Advantage in the Global Economy (CAGE) in the Department of Economics at the Univ. of Warwick, says, “This study has shown surprising results and I have decided it is prudent to eat more fruit and vegetables. I am keen to stay cheery.”