Definitions, regulations, and new frontiers for dietary fiber and whole grains

The aim of this article is to review the definitions and regulations for dietary fiber and whole grains worldwide and to discuss barriers to meeting recommended intake levels. Plant foods, such as whole grains, that are rich in dietary fiber are universally recommended in dietary guidance. Foods rich in dietary fiber are recommended for all, but dietary recommendations for whole grains and dietary fiber depend on definitions and regulations. Official recommendations for dietary fiber in the United States and Canada are denoted by dietary reference intakes (DRIs), which are developed by the Institute of Medicine. An adequate intake (AI) for dietary fiber was based on prospective cohort studies of dietary fiber intake and cardiovascular disease risk that found 14 grams of dietary fiber per 1000 kilocalories protected against cardiovascular disease (CVD). This value was used to set AIs for dietary fiber across the life cycle based on recommended calorie intakes. Actual intakes of dietary fiber are generally about half of the recommended levels. Recommendations for whole grain intake are equally challenging, as definitions for whole grain foods are needed to set recommendations. The 2005 Dietary Guidelines for Americans recommended that half of all grain servings be whole grains, but usual intakes are generally less than 1 serving per day, rather than the recommended 3 servings per day. Scientific support for whole grain recommendations is based on the same prospective cohort studies and links to CVD protection used to inform dietary fiber guidance. Thus, dietary fiber is a recommended nutrient and whole grains are a recommended dietary pattern in dietary guidance in North America and around the world. Challenges for attaining recommended intakes of dietary fiber and whole grains include low-carbohydrate diets, low-gluten diets, and public health recommendations to avoid processed foods.