The importance of fiber as a dietary component
Diets rich in dietary fiber and prebiotics are those with high levels of plant foods including fruits, vegetables, whole grains, legumes, nuts and seeds (Table 2 and Table 3). Such diets are associated with improved gastrointestinal, cardiovascular and metabolic health.9 In fact, the American Gut Study showed that eating 30 plant-based foods per week was associated with the highest levels of gut microbial diversity.10 In addition to their high fiber content, these foods also typically have a lower energy density and lower glycaemic index, and contain important micronutrients, essential fatty acids and other bioactive substances that contribute to overall health. EFSA recommends 25g dietary fiber per day for adults to promote adequate laxation, while recommendations for prevention of type 2 diabetes, cardiovascular disease, colorectal cancer, overweight and obesity are higher (25-38g/day).11 Some studies have found a greater risk reduction as more dietary fiber was consumed. However, this was not consistent across studies. Evidence is currently too limited to recommend specific types of fiber, so instead a diet rich in vegetables, fruits, and whole grain cereals is advised. There is less information available to set dietary fiber recommendations in children and current guidelines have been based on those for adults and vary according to energy requirements. EFSA suggests an intake of 2 g/MJ (megajoules) is considered adequate for normal laxation in children from the age of one year. There are no guidelines for fibre intake below 1 year of age. As research advances, recommendations should expand to include individual fibers and consider the effects and physiochemical properties of specific fiber rich foods in combination with other supplements.