The gut microbiota is under intense scientific investigation, as detailed in a recent review published in the journal Food & Function. This analysis focuses on the benefits of polyphenols—antioxidant substances found in fruits, coffee, green tea, and other foods—for the digestive tract, suggesting potential positive impacts on mental health.
Mario Marostica, a food engineer from the State University of Campinas (Unicamp), conducted this study in collaboration with the Federal University of Juiz de Fora, located in Minas Gerais. He emphasizes that polyphenols constitute one of the main groups of bioactive compounds present in vegetables. Among these compounds are the pigments responsible for the purplish and reddish hues of fruits such as grapes and jabuticaba.
Mechanisms of Benefit
Scientific literature has identified three central processes in the benefits provided by polyphenols. The first involves a targeted action on intestinal bacteria: on one hand, stimulating the growth of beneficial microorganisms; on the other, reducing the presence of potentially harmful strains.
The second mechanism is linked to metabolite production. Many polyphenols reach the large intestine without significant alteration, subsequently being converted into compounds that are more easily absorbed and possess biological activity. The third factor refers to short-chain fatty acids (SCFAs), which are produced by the bacteria themselves and help maintain the integrity of the intestinal barrier.
Gut-Brain Connection
Several studies demonstrate that these modifications in the microbiota positively influence mental state. This phenomenon is known as the gut-brain axis, a communication channel involving neurotransmitters linked to feelings of well-being, such as serotonin. Although polyphenols cannot cross the blood-brain barrier, they participate in signal transmission that can modulate emotions.
This interaction can occur through the vagus nerve, a structure originating in the brainstem, running all the way to the intestine, and reconnecting to the brain. Celso Cukier, a nutritionist at Einstein Israelite Hospital, observes that this system is already well documented and could become a future adjuvant in the treatment of conditions such as anxiety and depression.
For Cukier, studying the microbiota and the gut-brain axis represents one of the most promising scientific areas, and substances like polyphenols have the potential to be used alongside medications. However, he warns that more research is needed to determine which compounds are the most effective, in addition to the quantity and the profiles of people who would benefit most from this approach.
Composition and Function of Polyphenols
Also called phenolic compounds, polyphenols encompass approximately eight thousand members, classified according to their chemical structure. In nature, they are classified as secondary metabolites because they are synthesized by plants during their development to protect them against environmental adversities, such as ultraviolet rays, droughts, or heavy rains.
In our body, they play a protective role due to their antioxidant capacity, neutralizing free radicals—unstable molecules that require electrons to stabilize. By interrupting this reaction, they mitigate oxidative stress and protect cells. Furthermore, research indicates that these compounds have an anti-inflammatory effect.
Within the categories of polyphenols, flavonoids are the largest group, containing over five thousand cataloged substances and showing the most evidence regarding their effects. Anthocyanins, reddish and purplish pigments, belong to this group and are found in grapes, jabuticaba, and açai. There are also hesperidin and naringenin, examples of flavonoids found in citrus fruits. Other examples include quercetin (found in onions and apples), kaempferol (from broccoli), and catechin (from green tea). Coffee contains phenolic acids, notably caffeic acid, while red berries provide gallic acid.
The recommendation for incorporating polyphenols into the routine is to prioritize a diversified diet rich in vegetables, fruits, and greens. The researcher from Unicamp advises that consistency is crucial, since the effects of phenolic compounds seem to be more linked to habitual consumption than to sporadic and large-volume intakes.
It is essential to emphasize that the benefits are intrinsically linked to a healthy lifestyle, which includes not only diet but also physical exercise, adequate sleep, and stress management.