Blueberries influenced the microbiome and reduced symptoms of depression

The experiment involved 18 people over 65 years of age with mild depressive symptoms. All of them led a sedentary lifestyle. The participants were randomly divided into two groups: one group received 48 grams of blueberry powder daily (which is approximately two cups of fresh berries), while the other received a placebo. The powders were selected so as not to differ in appearance or taste, and the experiment was conducted in a blinded manner: neither the participants nor the researchers knew who was receiving what. The intervention lasted three months.

To track the effect of the berries, experts used several methods at once. The composition of the microbiota and gene activity were assessed using metagenomic sequencing. The level of short‑chain fatty acids in the stool was determined using liquid chromatography and mass spectrometry. And the severity of depressive symptoms was recorded using validated questionnaires — before the start and after the end of the experiment.

No differences were found in the overall composition of microbes or in the level of short‑chain fatty acids between the groups. However, within the group that received blueberries, statistically significant changes occurred in the activity of certain genes responsible for the functioning of microbial enzymes. Particularly interesting was the change in the expression of the EC 3.1.3.11 gene (Polyamine Transporting ATPase), which is involved in the production of gamma‑aminobutyric acid (GABA) — an important neurotransmitter that regulates the excitability of the nervous system.

At the same time, the difference in the reduction of depressive symptoms between the blueberry group and the placebo group did not reach the level of statistical significance. That is, it cannot be claimed that the berries unequivocally improved mood — the effect was noticeable, but it cannot be considered proven within the framework of this small study.

According to the lead author of the study, Courtney Millar, the goal was precisely to preliminarily assess how blueberries affect the microbiome, metabolites, and mood. The key role is likely played by fiber and anthocyanins — plant pigments that the berry is rich in. It is they that can change the environment in the gut and influence microbial processes, which, in turn, may be linked to mood.

It is important to take into account the limitations of the study: the sample size was very small, and the participants were predominantly women of European descent, so it is too early to generalize the results to all groups of older people. Furthermore, this was a pilot project: its purpose was not to provide a definitive answer, but to identify promising directions for further research.

Nevertheless, the data obtained look promising. If larger and longer‑term studies confirm that blueberries can indeed gently influence emotional well‑being through the microbiome, this could become one of the elements of non‑pharmacological support for older people with mild depressive symptoms.