Dietary fiber and prebiotics play significant roles in human health. Dietary fiber, originally defined as polysaccharides, now includes oligosaccharides based on their physiological effects. Prebiotics are non-digestible carbohydrates that selectively stimulate beneficial gut bacteria, such as Bifidobacteria and lactobacilli. Both fiber and prebiotics are fermented in the colon, producing short-chain fatty acids (SCFAs) that support gut health, immune function, and reduce inflammation. Prebiotics also enhance the growth of beneficial bacteria, improve gut barrier function, and may lower the risk of colon cancer. Dietary fiber is classified based on solubility and fermentation properties. Soluble fibers, like inulin and fructo-oligosaccharides, are more fermentable and may lower cholesterol, while insoluble fibers, such as wheat bran, promote bowel regularity. Fiber intake is linked to reduced cardiovascular disease risk, lower body weight, and improved glycemic control. However, the relationship between fiber and diabetes is complex, with some studies showing no significant effect. Prebiotics, such as inulin, oligofructose, and galactooligosaccharides, have been shown to improve gut microbiota composition, enhance SCFA production, and support immune function. They may also aid in weight management by promoting satiety and reducing calorie intake. However, prebiotic effects vary depending on the type and dose, and not all fibers are equally effective. Despite their benefits, the health claims for prebiotics and fiber are still under investigation. The U.S. Food and Drug Administration allows certain health claims for specific fibers, but more research is needed to fully understand their roles in disease prevention and health promotion. Overall, dietary fiber and prebiotics are important components of a healthy diet, contributing to gut health, immune function, and the prevention of chronic diseases.Dietary fiber and prebiotics play significant roles in human health. Dietary fiber, originally defined as polysaccharides, now includes oligosaccharides based on their physiological effects. Prebiotics are non-digestible carbohydrates that selectively stimulate beneficial gut bacteria, such as Bifidobacteria and lactobacilli. Both fiber and prebiotics are fermented in the colon, producing short-chain fatty acids (SCFAs) that support gut health, immune function, and reduce inflammation. Prebiotics also enhance the growth of beneficial bacteria, improve gut barrier function, and may lower the risk of colon cancer. Dietary fiber is classified based on solubility and fermentation properties. Soluble fibers, like inulin and fructo-oligosaccharides, are more fermentable and may lower cholesterol, while insoluble fibers, such as wheat bran, promote bowel regularity. Fiber intake is linked to reduced cardiovascular disease risk, lower body weight, and improved glycemic control. However, the relationship between fiber and diabetes is complex, with some studies showing no significant effect. Prebiotics, such as inulin, oligofructose, and galactooligosaccharides, have been shown to improve gut microbiota composition, enhance SCFA production, and support immune function. They may also aid in weight management by promoting satiety and reducing calorie intake. However, prebiotic effects vary depending on the type and dose, and not all fibers are equally effective. Despite their benefits, the health claims for prebiotics and fiber are still under investigation. The U.S. Food and Drug Administration allows certain health claims for specific fibers, but more research is needed to fully understand their roles in disease prevention and health promotion. Overall, dietary fiber and prebiotics are important components of a healthy diet, contributing to gut health, immune function, and the prevention of chronic diseases.