The gut microbiome plays a crucial role in modulating the risk of chronic diseases such as inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. Diet significantly influences the microbiome, with dietary changes leading to rapid shifts in microbial composition within 24 hours. This review examines how various dietary components affect the intestinal microbiota and their implications for human health. It highlights that specific foods alter the composition of host bacterial genera, which in turn influence immune and metabolic parameters. Understanding these associations is vital for both practitioners and patients. The human gut microbiome consists of trillions of microorganisms, primarily bacteria, which contribute to host health through vitamin synthesis, essential amino acid production, and metabolic byproducts from undigested dietary components. Short-chain fatty acids (SCFAs) like butyrate, propionate, and acetate serve as energy sources for intestinal epithelial cells and strengthen the mucosal barrier. The microbiome also influences local and systemic immunity through toll-like receptor (TLR) expression, antigen-presenting cells, T cells, and lymphoid follicles. Dietary changes, such as switching to a plant-based or animal-based diet, rapidly alter the microbiome within 24 hours. High-fat or high-sugar diets can disrupt circadian rhythms, while severe burn injuries can cause acute changes in the microbiome. The microbiome is associated with various diseases, including inflammatory bowel disease (IBD), autoimmune arthritis, type 2 diabetes, obesity, and atherosclerosis. For instance, IBD patients have reduced bacterial diversity and lower levels of butyrate-producing bacteria, which may contribute to inflammation. The microbiome also influences the development of Th17 cells, which are involved in autoimmune arthritis. Dietary protein, particularly animal-based protein, increases microbial diversity and the abundance of bile-tolerant bacteria like Bacteroides and Alistipes, while reducing beneficial bacteria like Roseburia. High-protein diets may increase the risk of cancer, diabetes, and mortality. Fats, especially saturated and trans fats, increase cardiovascular disease risk, while monounsaturated and polyunsaturated fats are beneficial. High-fat diets increase anaerobic microflora and Bacteroides abundance, while low-fat diets increase Bifidobacterium. Carbohydrates, particularly non-digestible ones like fiber, promote the growth of beneficial bacteria such as Bifidobacteria and Lactobacillus. Artificial sweeteners may be less healthy than natural sugars. Probiotics, such as those found in fermented dairy products, improve gut health and may reduce pathogen counts. Polyphenols, found in fruits, vegetables, and tea, have antioxidant properties and influence microbial composition. Popular diets like the Western diet reduce beneficial bacteria and increase harmful ones, while the Mediterranean diet, rich in fiber, polyphenols, and healthy fats, promotes a balanced microbiome. The gut microbiome significantly impacts hostThe gut microbiome plays a crucial role in modulating the risk of chronic diseases such as inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease, and cancer. Diet significantly influences the microbiome, with dietary changes leading to rapid shifts in microbial composition within 24 hours. This review examines how various dietary components affect the intestinal microbiota and their implications for human health. It highlights that specific foods alter the composition of host bacterial genera, which in turn influence immune and metabolic parameters. Understanding these associations is vital for both practitioners and patients. The human gut microbiome consists of trillions of microorganisms, primarily bacteria, which contribute to host health through vitamin synthesis, essential amino acid production, and metabolic byproducts from undigested dietary components. Short-chain fatty acids (SCFAs) like butyrate, propionate, and acetate serve as energy sources for intestinal epithelial cells and strengthen the mucosal barrier. The microbiome also influences local and systemic immunity through toll-like receptor (TLR) expression, antigen-presenting cells, T cells, and lymphoid follicles. Dietary changes, such as switching to a plant-based or animal-based diet, rapidly alter the microbiome within 24 hours. High-fat or high-sugar diets can disrupt circadian rhythms, while severe burn injuries can cause acute changes in the microbiome. The microbiome is associated with various diseases, including inflammatory bowel disease (IBD), autoimmune arthritis, type 2 diabetes, obesity, and atherosclerosis. For instance, IBD patients have reduced bacterial diversity and lower levels of butyrate-producing bacteria, which may contribute to inflammation. The microbiome also influences the development of Th17 cells, which are involved in autoimmune arthritis. Dietary protein, particularly animal-based protein, increases microbial diversity and the abundance of bile-tolerant bacteria like Bacteroides and Alistipes, while reducing beneficial bacteria like Roseburia. High-protein diets may increase the risk of cancer, diabetes, and mortality. Fats, especially saturated and trans fats, increase cardiovascular disease risk, while monounsaturated and polyunsaturated fats are beneficial. High-fat diets increase anaerobic microflora and Bacteroides abundance, while low-fat diets increase Bifidobacterium. Carbohydrates, particularly non-digestible ones like fiber, promote the growth of beneficial bacteria such as Bifidobacteria and Lactobacillus. Artificial sweeteners may be less healthy than natural sugars. Probiotics, such as those found in fermented dairy products, improve gut health and may reduce pathogen counts. Polyphenols, found in fruits, vegetables, and tea, have antioxidant properties and influence microbial composition. Popular diets like the Western diet reduce beneficial bacteria and increase harmful ones, while the Mediterranean diet, rich in fiber, polyphenols, and healthy fats, promotes a balanced microbiome. The gut microbiome significantly impacts host