University studies are often accompanied by increased workloads, sleep deprivation, and emotional strain, which is why researchers continue to investigate how diet affects mental health. Scientists are particularly interested in polyphenols—natural compounds present in berries, fruits, vegetables, tea, and cocoa. Earlier studies have shown that a diet rich in plant-based foods, such as the Mediterranean diet, is linked to a lower risk of developing depression.
Researchers from King’s College London set out to determine whether daily consumption of cranberry juice could influence mood, memory, and stress levels among students. The experiment included 72 healthy upper-year students aged 20 to 26. Over a 12-week period, one group drank 236 milliliters of cranberry juice each day, containing 442 milligrams of polyphenols, while the other group received a placebo—a beverage with a similar taste and color but without the active compounds.
During the study, specialists assessed mood, anxiety, stress, and depressive symptoms using specialized questionnaires. Participants also completed tests for memory and attention and provided saliva, blood, and urine samples to measure cortisol levels—the stress hormone—along with polyphenol metabolites. Based on subjective reports, no significant differences were found between the two groups: mood and anxiety indicators remained largely unchanged regardless of which drink was consumed.
However, objective results were more noticeable. After 12 weeks, students who regularly consumed cranberry juice showed lower cortisol levels. Additionally, they performed better on tests measuring short-term and verbal memory. Blood and urine analyses confirmed that polyphenols from the juice were effectively absorbed by the body, with higher concentrations associated with reduced stress hormone levels. Still, the researchers emphasized that the observed relationship is correlational and does not prove a direct cause-and-effect link.
The authors of the study believe that cranberry juice may potentially have a beneficial effect on memory and the body’s ability to handle stress. Nevertheless, the current evidence is insufficient to recommend it as a tool for improving mental health. According to the researchers, the greatest benefits come from a varied diet rich in plant-based foods, including berries, vegetables, whole grains, nuts, and tea, with cranberries being just one component of such an approach.
About the Author
