Dietary fiber guidelines in the Exchange Lists for Menu Planning. Should they be revised?

What is a high fiber diet?

There is no recognized definition of what constitutes a high fiber diet. Intakes of dietary fiber in different populations internationally vary widely from less than 20 g to more than 80 g per day. The types of foods contributing fiber also vary; in some countries cereals contribute the most fiber, in others leafy or root vegetables predominate. Vegetables have the highest fiber content per Kcal, and in most populations with fiber intakes over 50 g, vegetables contribute over 50% of total fiber intake. In rural Uganda, where the fiber hypothesis was first developed by Burkitt and Trowell, vegetables contribute over 90% of fiber intake. An experimental diet, the "Simian" diet, has been developed to mimic as closely as possible using human foods, the diet consumed by our simian ancestors the great apes. It is also similar to the Ugandan diet in containing large amounts of vegetables and 50 g fiber/1000 Kcal. Though nutritionally adequate, this diet is very bulky and not a suitable model for general recommendations. Dietary guidelines are that fat intake should be < 30% of energy, with a fiber intake of 20-35 g/d. These recommendations are inconsistent with a high fiber diet because, for people consuming more than about 2400 Kcal, low fiber choices for fruits and grains must be selected to keep dietary fiber intake within the range of 20-35 g. In a 30% fat, 1800 Kcal omnivorous diet, selection of wholemeal bread and whole fruit, results in a fiber intake over 35 g/d, and for and 1800 Kcal vegetarian diet, with substitution of modest amounts of peanut butter and beans for meats, dietary fiber intake goes up to 45 g/d. Thus, if it is desirable to promote the use of unrefined foods, the recommended dietary fiber intake should be a minimum of 15-20 g/1000 Kcal.

Database and quick methods of assessing typical dietary fiber intakes using data for 228 commonly consumed foods

To promote assessment of dietary fiber intakes in clinical settings, we established two objectives for this study: to provide a detailed database in grams per serving of fiber content and polymer composition for most fiber sources in the US diet, and to develop a quick method for estimating total fiber intakes. Data for 342 foods were condensed to 228 foods by combining similar foods. The comprehensive database developed includes pectin, hemicelluloses, and beta-glucan contents of the soluble and insoluble fractions of fiber and the cellulose and Klason lignin contents of the insoluble fiber. Three fourths of the 228 foods contained 2.0 g fiber per serving or less; only 10% contained more than 3.0 g per serving. The quick method consists of multiplying the number of servings in each food group by the mean total dietary fiber content of foods in that group: 1.5 g for fruits (n = 43), 1.5 g for vegetables (n = 68), 1.0 g for refined grains (n = 80), and 2.5 g for whole grains (n = 13). Actual fiber values from the database should be used in the quick method if foodstuffs concentrated from grains, legumes, and nuts and seeds are consumed. Sample menus demonstrate that quick assessment of total fiber intake yielded results similar to the sum of individual values from the database.

Macronutrient and energy database for the 1995 Exchange Lists for Meal Planning: a rationale for clinical practice decisions

For more than 50 years the exchange lists have been one method of meal planning for persons with diabetes as well as for those on weight-loss regimens. Little research has been conducted, however, concerning the methodologic basis of the system or its clinical effectiveness. Justification for specific food inclusions and general food groupings for the 1995 revision of the Exchange Lists for Meal Planning is provided by a database of foods and associated energy and macronutrient values. The mean energy and macronutrient values for each of the lists and sublists (starch, fruit, milk, and vegetables from the carbohydrate group; the meat and meal substitutes group, and the fat group) closely match the mean exchange values; however, the standard deviation and range are large. Interpretation of the database provides a rationale and guidance for decision making in clinical practice when using exchanges for meal planning, recipe, and food label calculations.