Effects of Physical Activity on Brain White Matter Integrity Are Region-, Dose-, and Age-Dependent: Findings From the Population-Based Rhineland Study.

For many years, human health was primarily examined through individual physiological systems. However, increasing scientific interest in the gut microbiota has substantially changed this perspective. The gut microbiota, which consists of trillions of microorganisms inhabiting the gastrointestinal tract, plays an active role in numerous physiological processes. These include immune regulation, metabolic balance, control of inflammatory responses, and modulation of neurological pathways. Accordingly, the microbiota is now considered a key component of a holistic understanding of health rather than merely a digestive element. The composition and diversity of the gut microbiota are influenced not only by genetic factors but also by everyday lifestyle behaviors. Among these, dietary habits represent one of the most powerful and modifiable determinants. Diets rich in dietary fiber, together with regular consumption of fermented and probiotic foods, have been associated with increased beneficial microorganisms and greater microbial diversity. In contrast, frequent intake of highly processed foods and imbalanced dietary patterns has been linked to adverse alterations in the gut microbiota, commonly described as dysbiosis. Probiotics are defined as ‘live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. This definition implies that probiotic status requires strain-specific characterisation and evidence of a clinically relevant health effect. Fermented foods, by contrast, are defined as ‘foods made through desired microbial growth and enzymatic conversions of food components. Although many fermented foods such as yogurt and kefir may contain live microorganisms, not all fermented foods qualify as probiotics particularly those subjected to heat treatment (e.g., tarhana) or pasteurisation (e.g., commercially processed pickles), which may reduce or eliminate viable microbial populations.