Summary: A randomized controlled tria demonstrated that incorporating a single glass of 100% fruit juice or a smoothie into a daily diet can significantly improve mental wellbeing and lower depression markers.
The four-week clinical trial evaluated adults with chronically low fruit and vegetable intakes. While targeted educational and financial support successfully helped participants hit the UK’s recommended “5-a-day” health milestone, the cohort that utilized fruit juice or smoothies scored significantly lower for markers of depression without experiencing any adverse metabolic side effects.
Key Facts
- The 5-a-day Nutritional Deficit: Consuming recommended daily quantities of whole fruits and vegetables is directly linked to better long-term health and a decreased risk of chronic disease. However, fewer than 17% of UK adults and only 10% of teenagers currently meet these baseline standards.
- The Controlled Trial Blueprint: Researchers monitored 42 adult participants who initially consumed two or fewer daily portions of produce. All subjects were given targeted financial and educational support to eliminate common barriers to healthy eating. One group was directed to hit the 5-a-day target using whole produce only, while the second group fulfilled the target by adding a small daily glass of 100% fruit juice or a smoothie.
- Quantifiable Mental Health Gains: Using validated questionnaires to measure anxiety and depression, scientists found that the juice-and-smoothie group recorded a modest but statistically significant drop in depression scores compared to the whole-produce control group. Their scores dropped by 2.52 points on a standard 27-point scale.
- No Displacement of Dietary Fiber: A common concern with juice consumption is that it might displace fiber-rich whole foods. However, dietary recalls showed that both testing groups successfully boosted their daily fiber intake by 8 to 10 grams, proving juice inclusion did not prevent participants from eating whole fruits and vegetables.
- Zero Metabolic Disadvantage: Despite lingering public health concerns regarding the sugar content of fruit juices, the study tracked metabolic health markers over the four-week window and recorded absolutely zero adverse metabolic effects among juice and smoothie drinkers.
- Cost-Effective Intervention: Senior study investigators emphasize that high fresh produce prices driven by economic cost-of-living pressures operate as a major barrier to clean eating. Utilizing a daily glass of 100% juice or a smoothie serves as an accessible, affordable tool to bridge the nutritional gap while optimizing brain blood flow and mental wellness.
Source: Newcastle University
People who drink a glass of 100% fruit juice or a smoothie each day as part of the UKโs 5-a-day healthy eating guidance see improvements in their mental wellbeing, according to new research from Newcastle University, UK.
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: โWhile most people know eating 5-a-day can be good for your health, many people struggle to.
โOur 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.โ
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 4-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 participantsโ 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: โGiven 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.
โThe 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 changesโlike increasing fruit intake, including through a daily glass of juiceโcould play a role in supporting mental wellbeing.โ
Study Design
In the 4-week trial, 42 participants who all consumed two or fewer portions of fruit and vegetables at the start of the study, were randomly divided into three groups.
The first group of 14 was a control group who were asked to maintain their usual diet throughout the study. The second group of 14 was given support to increase their fruit and vegetable intake to 5-a-day by consuming whole fruit and vegetables only, whilst the final group of 14 were asked to consume whole fruit and vegetables and include one daily glass of fruit juice or smoothie in their diet.
All groups received ยฃ10/week, with groups 2 and 3 also given educational material to help support their dietary changes.
The impact of the dietary changes on participantsโ mood was measured using validated questionnaires for anxiety (GAD-7 โ Generalised Anxiety Disorder 7) and depression (PHQ-9 โ Patient Health Questionnaire-9).
The group consuming fruit juice and smoothies alongside whole fruit scored statistically significantly lower for markers of depression compared to the control group. The scores were 2.52 points lower on a 27-point scale in the group consuming fruit juice versus the control โ with the adjusted mean score of 5.45 for control group and 2.93 for the group including fruit juices.
During the study, participants also completed dietary recalls four times about their diet in the previous 24 hours. Both intervention groups were estimated to have increased their fibre intake by 8-10g per day.
Key Questions Answered:
A: It provides a highly concentrated, accessible source of brain-boosting nutrients. The study from Newcastle University highlights that simple dietary improvements can directly alter brain function. This liquid intervention aligns with previous neurological data showing that the specific compounds found in citrus and whole fruit juices improve overall blood flow to the brain and optimize cognitive performance, directly pushing back against low mood states.
A: This trial specifically monitored that risk and found no negative consequences. Even with ongoing public debates surrounding the natural sugars found in juices, tracking the participants’ internal metabolic health markers across the four-week study revealed zero adverse side effects. When consumed as a balanced portion to hit your nutritional targets, juice operates as a safe, highly effective health elevator.
A: Because fresh, whole produce is often incredibly expensive and difficult to integrate into a busy life. With massive cost-of-living pressures stretching household budgets, buying fresh berries or vegetables acts as a major financial barrier for millions of families. A daily glass of 100% fruit juice or a blended smoothie provides a practical, highly shelf-stable, and cost-effective solution to help people easily conquer their nutritional targets.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this diet and depression research news
Author:ย Helen Rae
Source:ย Newcastle University
Contact:ย Helen Rae โ Newcastle University
Image:ย The image is credited to Neuroscience News
Original Research:ย Open access.
โIncluding 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 healthโ by Courtney Neal, Georg Lietz, Kirsten Brandt, Anthony W. Watson, and Oliver M. Shannon.ย British Journal Of Nutrition
DOI:10.1017/S0007114526107569
Abstract
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
Consuming fruit juice/smoothies could help overcome barriers to fruit and vegetable (F&V) intake. However, their contribution towardsย F&Vย intake within a healthy diet is contentious. We investigated howย F&Vย intake is affected by UK 5-a-day advice, with and without one portion/day of fruit juice/smoothies and explored how these interventions impacted markers of health.
Healthy individuals (n=42) with lowย F&Vย intake (โค2 servings/day) completed a four-week, parallel-group randomised controlled trial (ClinicalTrials.gov ID: NCT06628401). Participants were randomised to 1) control, 2) wholeย F&Vย (FV), or 3) wholeย F&Vย plus fruit juice/smoothies (FV+FJ). All groups received weekly financial support (to remove financial barriers toย F&Vย purchase in the intervention groups). FV and FV+FJ also received a co-designed educational booklet.
We investigated the intervention effects on self-reportedย F&Vย intake (primary outcome), biomarkers of intake and metabolism, mood, gut symptoms, and acceptability. Post-interventionย F&Vย intake differed between groups (p<0.001;ย ฮทp2=0.62). It was significantly higher in FV ((estimated marginal means [SE]); 8.9 [0.64] portions/day,ย p<0.001) and FV+FJ (6.6 [0.64],ย p<0.001) versus control (2.45 [0.64]), but there was no difference between FV and FV+FJ (p=0.051). Both interventions showed good acceptability.
Depression symptoms differed between groups (p=0.01;ย ฮทp2=0.21); they were significantly lower in FV+FJ than control. There were no differences in anxiety or gut symptoms, nor in intake or metabolic biomarkers.
A financial and educational intervention based on UK 5-a-day recommendations, with or without fruit juice/smoothies, significantly increased short-termย F&Vย intake and benefited mood without adversely impacting health markers in the short-term.
