Participants were instructed to drink 5 oz. of fluid per day with each muffin in addition to the 9 oz. juice mixture and their usual fluid intake; during the baseline segment they were to drink an additional 28 oz. of fluid per day as this amount was provided with the supplements. Subjects could reduce their intake of dietary fiber once during the study if they reported that they were not tolerating the supplements, and the reduced amount was maintained for the remainder of the study. The reduced amount of fiber was 10 g of total fiber per day and was distributed in the juice and muffin proportionally to the original supplement.
Design and Procedures
This study had a longitudinal, pre-post, among-groups design. The protocol of the parent study was 52 days in length and divided into the following segments: a 14-day baseline segment, a 6-day incremental dosing segment, an 18-day steady dose 1 segment, and a 14-day steady dose 2 segment (Figure 1). During the incremental dosing segment, the amount of fiber administered was gradually increased by one-third every two days to the total of 16 g of total fiber per day. Participants consumed 16 g of total fiber per day during the steady dose 1 and steady dose 2 segments unless a subject required a reduction in the amount of dietary fiber in the supplement (as explained above). During the steady dose 2 segment, the same type of data was collected as during the baseline segment. In determining the length of the segments of the parent study, past research and subject burden were considered. In a previous study, clinical effects from dietary fibers were seen in approximately two weeks of taking a steady dose of fiber. Advancing the amounts of dietary fiber over six days seemed to promote tolerance of any flatus that occurred (Bliss et al., 2001). Past experience informed suitable lengths of data collection for planned analyses and overall participation that promoted completion of the study by subjects.