By suppressing fermentation, silymarin may help reduce excessive energy extraction, revealing a potential new mechanism of action. This effect was observed at low concentration, indicating that higher doses, such as those found in supplements, could lead to a more pronounced impact, warranting further investigation. DIABLO analysis confirmed the previously reported differences in fecal microbial composition between healthy young and healthy elder subjects. We have shown that these differences are associated with a change in silymarin degradation and catabolite production. Our study revealed a higher abundance of the genera Lachnospiraceae UCG-010, Lachnospiraceae UCG-004, Ruminococcaceae UCG-003 and Erysipelotrichaceae UCG-003 in the microbiome of healthy young donors. This is a confirmation of previously known differences between microbiota of young and elderly people. The Lachnospiraceae and Ruminococcaceae families are frequently associated with the production of SCFAs. In contrast, there is no direct evidence specifically addressing the role of the Erysipelotrichaceae family in SCFA production. However, studies have highlighted its potential impact on gut health and metabolic disorders. The higher abundance of these taxa of Lachnospiraceae and Ruminococcaceae family is linked to young age and better health outcomes. It is increased in subjects with lower total cholesterol levels. Higher abundances of Lachnospiraceae UCG-010 and Lachnospiraceae UCG-004 were also observed in individuals with higher intakes of certain other polyphenols. Similarly, the genus Ruminococcaceae UCG-003 is associated with a lower risk of the metabolic syndrome, dyslipidemia, and other cardiometabolic diseases. In our study, all these strains were also associated with faster degradation (lower area under the curve) of silybin A and isosilybin B. These genera were also associated with the formation of the catabolite 469.113@11.9, suggesting their involvement in the degradation of silybin A and isosilybin B via demethylation, leading to the formation of the catabolite 469.113@11.9.