In a randomised controlled trial, adults with low fruit and vegetable intake were given support to increase their daily consumption, with some participants adding a glass of fruit juice or a smoothie to their diet to help meet the 5-a-day recommendation.

After four weeks, both groups had successfully increased their fruit and vegetable intake. However, participants who included fruit juice or smoothies in their diet reported a reduction in depression scores.

The findings, which have been peer-reviewed and published in the British Journal of Nutrition, add to growing evidence that simple dietary changes may support mental wellbeing. The study was funded by the Fruit Juice Science Centre.

Dr Courtney Neal, who completed the study while at Newcastle University and is now at the University of Liverpool, said: "While most people know eating 5-a-day can be good for your health, many people struggle to."

"Our trial showed that when people with low fruit and vegetable intake were provided with targeted financial and educational support to address common barriers to eating 5-a-day, they were able to make meaningful changes to their diet. We found that simple, cost-effective solutions, like drinking a small glass of 100% fruit juice or a smoothie daily, could help people reach their 5-a-day, with potential benefits for mental wellbeing," Neal said.

Hitting the targets

Eating the recommended amount of whole fruits and vegetables is associated with a lower risk of chronic disease and better long-term health. However, fewer than one in five (17%) UK adults and one in 10 teenagers currently meet the recommended 5-a-day target.

In the four-week trial, all participants were consuming two or fewer portions of fruit and vegetables per day at the beginning of the study. They were then given support to increase their intake to five portions a day.

One group was instructed to consume whole fruits and vegetables only, while the other consumed whole fruits and vegetables along with one daily glass of fruit juice or a smoothie.

The researchers assessed changes in participants' mood using validated questionnaires measuring anxiety and depression. The group that consumed fruit juice or smoothies alongside whole fruits and vegetables recorded lower depression scores than the control group.

The scores were 2.52 points lower on a 27-point scale, representing a modest but statistically significant difference.

Both intervention groups were estimated to have increased their fibre intake by 8-10 grams per day, based on dietary recalls completed during the study. This suggested that consuming juice did not prevent participants from increasing their intake of other fibre-rich fruits and vegetables.

Despite ongoing concerns about sugar content, the study, which involved 42 participants, found no adverse effects on metabolic health markers after four weeks among those who consumed fruit juice or smoothies as part of the intervention.

Dr Oliver Shannon, Lecturer in Nutrition and Ageing at Newcastle University and one of the study's senior authors, said: "Given the ongoing cost of living pressures in the UK, the price of fresh produce is often a barrier for people trying to eat more fruit and vegetables.

"Our study shows that drinking a daily glass of fruit juice or a smoothie could be part of the solution and help people reach 5-a-day fruit and vegetable targets."

He added that the finding of lower depression scores among fruit juice consumers was "promising" and warranted further research, particularly among people experiencing poor mental wellbeing.

"It backs up studies which report improved brain blood flow and cognitive function after people drink citrus juices. Simple dietary changes—like increasing fruit intake, including through a daily glass of juice—could play a role in supporting mental wellbeing," Shannon said.