Vegetable dietary fibres made with minimal processing improve health-related faecal parameters in a valid rat model.

Dietary fibre-induced faecal bulking and hydration are important contributors to large bowel function and health, and are affected by the dietary fibre structure. To determine faecal bulk-related parameters for vegetable dietary fibres with retained structure, cold water fragmentation of vegetables was used to make minimally processed vegetable fibres (MPVF) from swede, broccoli and asparagus. A valid adult rat model was used to subject the fibres to processes of hind gut fermentation and faecal accumulation similar to those in humans. All the MPVFs had high faecal bulking indexes (FBIs, mean ± sem: wheat bran (reference), 100 ± 6.0; asparagus 168 ± 5.7; swede 135 ± 6.1; broccoli 135 ± 5.9; broccoli rind 205 ± 10.4), and caused large increases in the theoretical colonic water load at 10 g per 100 g diet (increase over baseline (%): wheat bran, 137 ± 8.3; asparagus, 236 ± 25, swede 193 ± 8.8; broccoli 228 ± 12; broccoli rind 223 ± 8.5). Faecal bulking by MPVFs was much greater than by fermentable extracted polysaccharides such as pectin and raftilose, or by commercial fibres made from highly processed cell walls. The results show natural, non-degraded vegetable fibres with retained botanical structure have beneficial effects not provided by structure-less fermentable dietary fibres. Dietary fibre-deficient diets supplemented with prebiotics cannot, therefore, adequately substitute for varied diets containing adequate vegetables, fruits and wholegrain cereals in which fermentation is associated with enough retained structure to conserve physicochemical properties of benefit to colonic function.

No difference in fecal levels of bacteria or short chain fatty acids in humans, when consuming fruit juice beverages containing fruit fiber, fruit polyphenols, and their combination.

This study examined the effect of a Boysenberry beverage (750 mg polyphenols), an apple fiber beverage (7.5 g dietary fiber), and a Boysenberry plus apple fiber beverage (750 mg polyphenols plus 7.5 g dietary fiber) on gut health. Twenty-five individuals completed the study. The study was a placebo-controlled crossover study, where every individual consumed 1 of the 4 treatments in turn. Each treatment phase was 4-week long and was followed by a 2-week washout period. The trial beverages were 350 g taken in 2 doses every day (ie, 175 mL taken twice daily). The hypothesis for the study was that the combination of polyphenols and fiber would have a greater benefit on gut health than the placebo product or the fiber or polyphenols on their own. There were no differences in fecal levels of total bacteria, Bacteroides-Prevotella-Porphyromonas group, Bifidobacteriumspecies, Clostridium perfringens, or Lactobacillus species among any of the treatment groups. Fecal short chain fatty acid concentrations did not vary among treatment groups, although prostaglandin E2 concentrations were higher after consumption of the Boysenberry juice beverage. No significant differences were found in quantitative measures of gut health between the Boysenberry juice beverage, the apple fiber beverage, the Boysenberry juice plus apple fiber beverage, and the placebo beverage.