Adults who added a daily glass of fruit juice or a smoothie to a diet already rich in fruit and vegetables reported lower depression scores after just four weeks, according to a new randomised controlled trial from Newcastle University in England.
The study recruited people who were eating two or fewer portions of fruit and vegetables a day, well below the five-a-day target recommended by the UK's National Health Service and similar guidelines followed across much of Europe. Researchers gave all participants support to raise their intake, but only some were asked to include a daily glass of 100% fruit juice or a smoothie alongside whole produce.
What the trial found
After four weeks, both groups had successfully increased how much fruit and vegetables they ate. But the group that included juice or a smoothie reported a meaningful drop in depression scores compared with the group eating whole fruit and vegetables alone.
The juice group scored 2.52 points lower on a 27-point scale used to measure depressive symptoms, a difference researchers describe as modest but statistically significant. Dietary recalls suggested both groups increased their fibre intake by roughly 8 to 10 grams a day, indicating that drinking juice did not stop participants from also eating more whole produce.
“"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," said Dr Courtney Neal, who led the study while at Newcastle University and now works at the University of Liverpool.”
A small study with caveats
The trial involved just 42 participants and ran for only four weeks, limits the researchers themselves acknowledged when reporting the results, first detailed by ScienceDaily. Such a small sample makes it harder to know whether the effect would hold in a larger, more diverse population, or across different countries and diets.
The research was also funded by the Fruit Juice Science Centre, a body linked to the juice industry, which is worth noting given ongoing debate in nutrition science over how fruit juice compares with whole fruit. Some larger observational studies have linked high juice consumption to weight gain or even worse mental health outcomes, making this trial something of an outlier worth further scrutiny rather than a final word.
Still, the authors argue the finding fits with other research pointing to benefits from citrus compounds for blood flow to the brain and cognitive function. The peer-reviewed study appeared in the British Journal of Nutrition, and the researchers say it adds to a wider body of evidence that practical, low-cost dietary changes can play a supporting role in mental wellbeing.
For readers across Europe, where fruit and vegetable intake often falls short of national guidelines and juice is widely available in supermarkets, the study offers a modest but intriguing data point. Nutritionists are likely to stress that it should be read alongside broader dietary advice rather than as a standalone remedy for depression, and that anyone experiencing persistent low mood should speak to a doctor rather than rely on dietary changes alone.
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