Research has shown that consumption of high fiber breakfast cereal is associated with improved subjective well-being, especially increased energy. One possible explanation of these results is through metabolism by gut bacteria and concomitant production of metabolites that influence psychological and gastrointestinal (GI) welfare. This was examined in the present study to determine whether consumption of wheat bran could modulate the composition of the GI microbiota. This human volunteer study (20 volunteers) involved the comparison of three breakfast cereals, All-Bran, Bran Flakes and Cornflakes (60 g/d). The study involved a 14-day baseline phase (no breakfast cereals) and an eight-week experimental phase. Each cereal was consumed for 14 days. A seven-day washout period (no cereals) was carried out between each successive cereal condition. Faecal samples were collected every seven days. Enumeration of predominant faecal bacterial populations (bacteroides, bifidobacteria, clostridia, lactobacilli and eubacteria) was carried out using the culture independent fluorescent in situ hybridisation (FISH) technique. Faecal short chain fatty acid content was also determined. The volunteers completed a battery of questionnaires to assess fatigue/energy, subjective mood, physical and mental health, bowel function and fiber intake. The results showed that in general there was no overall significant effect of breakfast cereal type on the faecal bacterial populations studied. There was also no major effect of breakfast type on short chain fatty acid content. The high-fiber conditions (All-Bran and Bran Flakes) were associated with less fatigue, a significant reduction in cognitive difficulties, looser stools, more motions and feeling more energised.
The short-chain fatty acid content in the caecal
digesta of rats fed diets with various sources of
fibre