In a new randomised controlled trial, adults with low intakes of fruit and vegetables were given support to increase their daily fruit and vegetable intake, with or without a glass of fruit juice or a smoothie, in order to meet the 5-a-day guideline.

After four weeks, both groups successfully boosted their fruit and vegetable intake but the group of people who added in fruit juice reported a reduction in depression scores.

The results, peer-reviewed and published in the British Journal of Nutrition and funded by the Fruit Juice Science Centre, add to growing evidence that simple, practical dietary changes can support mental health.

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.”

Hitting the targets

Eating the recommended target of whole fruit and vegetables is linked to a lower risk of chronic disease and better long-term health. However, fewer than 1 in 5 (17%) UK adults and 1 in 10 teenagers currently meet the recommended 5-a-day.

In the four-week trial, participants who all consumed two or fewer daily portions of fruit and vegetables at the start of the study, were given support to increase their intake to 5-a-day. Some were told to consume whole fruit and vegetables only, whilst others consumed whole fruit and vegetables and included one daily glass of fruit juice or smoothie in their diet. 

The impact of the dietary changes on participants’ mood was measured using validated questionnaires for anxiety and depression. The group consuming fruit juice and smoothies alongside whole fruit scored lower for markers of depression compared to the control group. The scores were 2.52 points lower on a 27-point scale, reflecting a modest but statistically significant difference.

Both intervention groups were estimated to have increased their fibre intake by 8-10g per day, according to dietary recalls they completed during the study, suggesting that drinking juice did not prevent participants from increasing their intake of other fibre-rich fruits and vegetables.

Despite ongoing concerns around sugar content, the study of 42 participants also found no adverse effects on metabolic health markers after the four-week period among participants consuming fruit juice and smoothies as part of the intervention.

Dr Oliver Shannon, Lecturer in Nutrition and Ageing at Newcastle University and one of the senior authors of the study, 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.

“The finding that fruit juice drinkers had reduced depression scores is promising and worthy of further exploration, particularly in individuals 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.”

Reference:  Including fruit juice and smoothies within 5-a-day fruit and vegetable intake recommendations: A randomised controlled trial investigating impact on levels of intake, mood, and markers of health. Journal: British Journal of Nutrition. DOI: https://DOI.org/10.1017/S0007114526107569

Press release courtesy of the Fruit Juice Science Centre