Five to seven daily serves of fruit and vegetables has been linked to a lower incidence of psychological stress among the over 45s.

The more fruit and vegetables people eat, especially women, the less stress they feel, according to new research.

A longitudinal study of more than 60,000 Australian men and women aged 45 and over found eating five to seven daily serves of fruit and vegetables was associated with a 14 per cent lower incidence of psychological stress compared to those who ate less than this.

Three to four daily serves of vegetables alone was linked to a 12 per cent lower risk of stress than those who ate 0-1 serves daily.

The findings add to a growing body of evidence that supports the idea of using a high-quality diet as an intervention treatment for people with depression.

"There's growing awareness in that what we put into our mouths is closely linked to our mental state," said Dr Melody Ding of the University of Sydney's School of Public Health.

Researchers at the University of Sydney examined data from the Sax Institute's 45 and Up Study and found most of the effect on a person's mood, which was measured using the Kessler Psychological Distress Scale, was mostly driven by a moderate to high consumption of vegetables.

Combined consumption of fruit and vegetables was, however, more beneficial to women, said Dr Ding.

Women who ate five to seven daily serves of fruit and vegetables had a 23 per cent lower risk of stress than women who ate just one serve a day.

"This study is among the first to report associations between fruit and vegetable consumption and psychological well-being separately for men and women," the authors wrote.

"It is possible that there may be a true physiological difference between men and women, although a mechanism that could explain this difference remains unclear, or perhaps women more accurately report consumption of fruit and vegetables than men," the authors added.

The study is published in the British Medical Journal.

Earlier this year researchers at Deakin University's Food and Mood Centre showed the widely lauded Mediterranean diet to be a powerful treatment for major depression.

A randomised controlled trial found a third of the participants who followed the Mediterranean diet for three months met criteria for remission of major depression, compared to eight per cent of those who only received social support.

"These results were not explained by changes in physical activity or body weight, but were closely related to the extent of dietary change," said the centre's director Professor Felice Jacka.