and a modification of the original method was later adopted by the Association of Official Analytical Chemists International (AOAC) as a method for measuring fiber in animal feeds (AOAC, 1995). The crude fiber method was used for the determination of the fiber content for the U.S. Food Composition tables in the 1970s (Watt, 1976). It continues to be used in some regions of the world as well as the animal feed industry. However, its usefulness is severely limited by the loss of all soluble polysaccharides, some insoluble polysaccharides, and some lignin, and the inclusion of some nitrogenous material in the remaining residue.
In the 1960s, Van Soest and colleagues introduced the use of detergents to solubilize protein. The Acid Detergent Fiber (ADF) method, which was adopted for animal feeds, utilizes strong acid to hydrolyze all polysaccharides except cellulose and lignin, which are therefore the only components in ADF (Van Soest, 1963). Other cell wall polysaccharides are not included in this method, limiting its usefulness for human nutrition in the same way as crude fiber.
Recognizing the need to describe and include other cell wall constituents, Van Soest and Wine (1967) developed the Neutral Detergent Fiber (NDF) method, which measures all insoluble cell wall material. This proved to be a better predictor of the nutritional value of dietary fiber in animal feeds than crude fiber. In the 1970s, the use of the NDF method spread to human nutrition, but its utility remained limited because it did not include soluble fiber components nor did it remove all starch.
With growing interest in dietary fiber in human nutrition in the 1970s and the development of a physiological role for this dietary component, there was a need for an analytical method that measured insoluble cell wall and soluble fiber components. German researchers introduced the use of enzymes during the nineteenth century to remove available carbohydrate, and this approach was used by Williams and Olmsted (1935) in the United States in an effort to measure the indigestible material in a more physiological way in their human studies. Building on this work, a number of investigators, such as Asp and Johansson (1981), Furda (1977), Hellendoorn and colleagues (1975), and Schweizer and Würsch (1979), developed analytical approaches that reflected the “nondigested” fraction of the diet, including soluble material as well as insoluble components. Prosky and coworkers (1985) published a method that was based on the work of these various investigators, and it was subsequently adopted by AOAC as AOAC method 985.29. The method provides a measure of total dietary fiber by enzymatic removal of available starch and solubilization and extraction of a portion of the protein; the remaining residue is dried, weighed, and corrected for crude protein and ash contents. An initial step is added to remove fat if it is present at concentrations of 10 percent or more. The method is relatively rapid and easy to perform and has been automated to enable a large number of samples to be assessed. It has been adopted as an official method for dietary fiber analysis by many countries.