Dietary fiber: The prebiotic connection
Dietary fiber: the prebiotic connection
Dietary fiber intake is linked to improved health outcomes, including a lower risk of cardiovascular disease, improved glucose tolerance, lower obesity rate, and improved gut health. Certain dietary fibers also serve as prebiotics, compounds that promote the growth of colonic microflora.
Despite universal acceptance that fiber content in the diet is essential for good health, intake of dietary fiber in the United States is generally less than half of recommended levels. Because most foods are quite low in fiber, obtaining the recommended intake of fiber from foods is difficult without the inclusion of high-fiber cereals, legumes, foods with added fiber, or fiber supplements.
What is dietary fiber?
Dietary fibers are carbohydrates that are not digested or absorbed by humans.1 Fibers include both "dietary fiber," the fiber naturally occurring in foods, and "functional fibers," isolated fibers such as polydextrose, psyllium, and inulin, that are purified and have positive physiological effects. Dietary fiber is listed on the Nutrition Facts panel required on all packaging.
The FDA currently recommends 25 g of dietary fiber in a 2,000-kcal diet but has proposed to increase the recommended level to 28 g per day. Manufacturers are allowed to call a food a "good source of fiber" if it contains 10% of the recommended amount (2.5 g/serving) and an "excellent source of fiber" if the food contains 20% of the recommended amount (5 g/serving).
Dietary fiber on food labels includes both dietary fiber and functional fiber. Fiber intake is generally closely linked to calorie intake. Thus, recommendations to reduce calorie intake will make increasing fiber intake from food particularly challenging. Most studies find, on average, that fiber intake is about half of recommended levels and that 5% of Americans consume the recommended amount.
To consume amounts of fiber that are healthy for the colon itself and that promote the presence of a healthy gut microbiome, there is a need for additional fiber. This can be in the form of supplements, foods with added fiber, or by conscious intention to eat a number of high-fiber foods on a daily basis.