A Newcastle University trial has found that a simple daily habit—drinking a glass of 100% fruit juice or a smoothie—can lower depression scores in just four weeks.
The study, published in the British Journal of Nutrition, reveals an often-overlooked pathway to better mental health. In a world where fewer than 1 in 5 UK adults meet the recommended 5-a-day fruit and vegetable intake, researchers wanted to understand what happens when people actually reach that target. They recruited 42 adults with notably low fruit and vegetable consumption and split them into two groups: one that increased their intake through whole fruits and vegetables alone, and another that combined whole produce with a daily glass of fruit juice or smoothie.
After just four weeks, both groups successfully boosted their daily intake. But the results diverged in a meaningful way. Participants who included juice or smoothies alongside whole fruits and vegetables reported depression scores that were 2.52 points lower on a 27-point scale—a modest but statistically significant improvement. The control group, despite also increasing their fruit and vegetable intake, did not see the same mental health benefit.
The finding is particularly striking because it challenges a common assumption: that fruit juice, with its concerns about sugar content, might undermine overall health gains. The trial found no adverse effects on metabolic health markers among juice-drinking participants after the four-week period. In fact, both intervention groups increased their daily fiber intake by 8–10 grams, suggesting that juice drinkers were not replacing other fiber-rich foods but genuinely adding to their diet.
Dr. Courtney Neal, who led the study at Newcastle University and is now at the University of Liverpool, emphasized the practical accessibility of these findings. "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," she explained. "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 well-being."
Cost, in fact, may be why this finding matters so much. In an era of cost-of-living pressures, fresh produce remains out of reach for many households. Dr. Oliver Shannon, a senior author and lecturer in Nutrition and Aging at Newcastle University, noted that a daily glass of juice could be "part of the solution" for people struggling to afford fresh fruit and vegetables. The connection to mental health adds another layer of significance: as depression and anxiety affect millions, accessible, affordable interventions backed by rigorous evidence are rare.
The mechanism isn't entirely clear, but existing research hints at answers. Studies have reported improved brain blood flow and cognitive function after people drink citrus juices, suggesting that the nutrients in fruit—not just the general health benefit of increased produce consumption—may directly support mental well-being.
The trial is modest in size, and Dr. Shannon himself called the findings "promising and worthy of further exploration, particularly in individuals experiencing poor mental well-being." Yet it sits within growing evidence that simple dietary changes, far from requiring major upheaval, can meaningfully support mental health. For the millions struggling with depression and the many more trying to afford a healthier diet, that message offers genuine hope.