Table 1.

Factors affecting microbiota.

Factor	Impact on Gut Microbiota
Mode of Delivery [50,57,58]	Influences the initial colonization of a newborn’s GI tract. Vaginal delivery (VD) leads to a microbiota similar to maternal vaginal microbiota with a dominance of Lactobacillus spp. Cesarean section (CS) results in decreased diversity and an imbalance, with infants showing higher abundance of hospital pathogens and lower abundance of Bifidobacteria spp., Bacteroides spp., Staphylococcus spp., Corynebacterium spp., and Propionibacterium spp.
Probiotics [50]	Regulates the immune system, supports gut barrier integrity, and has been shown to alleviate symptoms of depression, anxiety, and stress. Specific strains like Lactobacillus helveticus R0052 and B. longum R0175 have shown benefits in mental health.
Stress [50,59]	Stress can decrease the number of beneficial species like Lactobacillus spp. and Bifidobacterium spp. while increasing pathogenic and non-pathogenic strains of E. coli and species from the genus Clostridium spp.
Circadian Clock System [50,60]	The circadian rhythm affects the diurnal fluctuations of GM. Stress and changes in the circadian clock system can cause dysregulation of the intestinal microbiota, leading to decreases in Lactobacillus and increases in pathogenic bacteria.
Occupational and Environmental Exposure [50]	Occupational and environmental pollutants, including heavy metals, pesticides, and PAHs can modify GM composition. Shift work and exposure to specific work environments can alter the microbiota, indicating potential health risks.
Diet [50,61]	Diet influences GM diversity and abundance, affecting metabolism and immune responses. Dietary fibers are fermented by GM to produce SCFAs, beneficial for colon health. Variations in diet, such as Mediterranean, ketogenic, vegetarian, or vegan diets, have significant impacts on GM composition.