In recent years, there has been a global trend towards a plant-based lifestyle. In the NuEva study, dietary self-reports of 258 participants following one of four diets (Western diet (WD), flexitarians (Flex), vegetarians (VG), and vegans (VN)) were related to fecal microbiome composition. Reduced consumption of animal products (VN < VG < Flex < WD) was associated with a decreased intake of energy (p < 0.05), and an increased intake of soluble and non-soluble dietary fibers (p < 0.05). We observed the lowest average microbiome diversity in vegans and the highest in WD. Compared to WD, VG (p < 0.05) and VN (p < 0.01) differed significantly in their bacterial composition. These data were related to dietary fiber intake. Furthermore, we identified 14 diet-specific biomarkers at the genus level by using LefSe analysis. Of these, 11 showed minimum or maximum counts in WD or VN. While the VN-specific species were inversely associated with cardiovascular risk factors, a positive association was detected for the WD-specific species. Identifying biomarkers for the diets on extreme ends of the spectrum (WD and VN) and their association with cardiovascular risk factors provides a solid evidence base highlighting the potential and the need for the development of personalized recommendations dependent on dietary patterns. Even so, the mechanisms underlying these diet-specific differences in microbiome composition cannot yet be clearly assessed. The elucidation of these associations will provide the basis for personalized nutritional recommendations based on the microbiome.

Insufficient dietary fiber intake can negatively affect the intestinal microbiome and, over time, may result in gut dysbiosis, thus potentially harming overall health. This randomized controlled trial aimed to improve the gut microbiome of individuals with low dietary fiber intake (<25 g/day) during a 7-week synbiotic intervention. The metabolically healthy male participants (n = 117, 32 ± 10 y, BMI 25.66 ± 3.1 kg/m²) were divided into two groups: one receiving a synbiotic supplement (Biotic Junior, MensSana AG, Forchtenberg, Germany) and the other a placebo, without altering their dietary habits or physical activity. These groups were further stratified by their dietary fiber intake into a low fiber group (LFG) and a high fiber group (HFG). Stool samples for microbiome analysis were collected before and after intervention. Statistical analysis was performed using linear mixed effects and partial least squares models. At baseline, the microbiomes of the LFG and HFG were partially separated. After seven weeks of intervention, the abundance of SCFA-producing microbes significantly increased in the LFG, which is known to improve gut health; however, this effect was less pronounced in the HFG. Beneficial effects on the gut microbiome in participants with low fiber intake may be achieved using synbiotics, demonstrating the importance of personalized synbiotics.

Synbiotics modulate the gut microbiome and contribute to the prevention of liver diseases such as metabolic-dysfunction-associated fatty liver disease (MAFLD). This study aimed to evaluate the effect of a randomized, placebo-controlled, double-blinded seven-week intervention trial on the liver metabolism in 117 metabolically healthy male participants. Anthropometric data, blood parameters, and stool samples were analyzed using linear mixed models. After seven weeks of intervention, there was a significant reduction in alanine aminotransferase (ALT) in the synbiotic group compared to the placebo group (−14.92%, CI: −26.60–−3.23%, p = 0.013). A stratified analysis according to body fat percentage revealed a significant decrease in ALT (−20.70%, CI: −40.88–−0.53%, p = 0.045) in participants with an elevated body fat percentage. Further, a significant change in microbiome composition (1.16, CI: 0.06–2.25, p = 0.039) in this group was found, while the microbial composition remained stable upon intervention in the group with physiological body fat. The 7-week synbiotic intervention reduced ALT levels, especially in participants with an elevated body fat percentage, possibly due to modulation of the gut microbiome. Synbiotic intake may be helpful in delaying the progression of MAFLD and could be used in addition to the recommended lifestyle modification therapy.

The global coronavirus disease 2019 (COVID-19) pandemic has affected multiple aspects of people’s lives, which may also influence the results of studies conducted during this period across diverse research domains. This particularly includes the field of nutritional science, investigating the gut microbiota as a potential mediator in the association between dietary intake and health-related outcomes. This article identifies the challenges currently facing this area of research, points out potential solutions, and highlights the necessity to consider a range of issues when interpreting trials conducted during this period. Some of these issues have arisen specifically because of the measures implemented to interrupt the spread of small acute respiratory syndrome coronavirus 2 (SARS-CoV-2), while others remain relevant beyond the pandemic.

Elite athletes undergo intense physical training and experience substantial physiological stress, which could affect the composition and function of their gut microbiome. This study compared the gut microbiomes of 148 German junior and senior elite athletes with those of 108 healthy adults to identify taxonomic and functional features associated with elite athletic status. Group comparisons were conducted between healthy adults, senior athletes, and junior athletes, and a matched-subgroup analysis was performed in adults only, controlling for age, sex, body mass index, and dietary pattern. Significant differences in taxonomic composition were observed between athletes and healthy adults. Healthy adults exhibited greater microbial evenness and diversity than junior athletes, whereas senior athletes displayed higher microbial richness. Principal coordinate analysis revealed distinct clustering by athletic status. Linear discriminant analysis effect size identified taxa such as Escherichia-Shigella as being enriched in athletes. Predictive metagenomic profiling (PICRUSt2) indicated differences in microbial functional potential between adult athletes and matched controls, including pathways related to amino acid metabolism, glycolysis, fatty acid β-oxidation, and quinone biosynthesis. Together, these findings demonstrate distinct taxonomic and predicted functional microbiome signatures associated with elite athletic status. IMPORTANCE: Elite athletic training and lifestyle are associated with the gut microbiome. Our research has revealed distinct microbial structures in elite athletes, characterized by reduced evenness in junior athletes and increased richness in senior athletes, compared to healthy adults. Matched-subgroup analyses confirmed these group-specific differences. The gut microbiomes of athletes were enriched in pathways related to amino acid biosynthesis, glycolysis, fatty acid β-oxidation, and quinone synthesis. These microbiome features may be relevant for metabolic efficiency and resilience to oxidative stress. Combining taxonomic and functional prediction data from a uniquely characterized cohort of junior and senior elite athletes provides novel insight into microbiome signatures associated with sustained physical and psychological stress, with potential implications for performance, recovery, and health. CLINICAL TRIALS: This study is registered with ClinicalTrials.gov as NCT03582020 .

Oats (Avena sativa) are a valuable food source known for their multiple beneficial physiological effects due to their unique nutrient composition, including high levels of dietary fiber, especially...