Abstract
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.
Highlights
There is considerable evidence that constipation and other disorders of bowel functioning are significant causes of morbidity (Garrow & James, 1993)
The major aims of the present human study were to confirm that consumption of wheat bran cereals increase energy and reduce cognitive difficulties
A secondary aim was to determine whether wheat bran cereals have a prebiotic effect that could explain behavioural effects associated with consumption of these cereals
Summary
There is considerable evidence that constipation and other disorders of bowel functioning are significant causes of morbidity (Garrow & James, 1993). An intervention study was carried out to determine whether increasing fiber intake, by consuming All-Bran or Bran Flakes, was associated with changes in bowel functioning and physical/mental health. Results suggested that increased dietary fiber from wheat bran cereals reduced fatigue This effect did not depend on the removal of symptoms of bowel dysfunction. Many dairy products have added live additions of health promoting bacteria as probiotics (Hill et al, 2014), whilst the fermentation of certain carbohydrates (prebiotics) can selectively enhance beneficial components of the gut microbiota, such as lactobacilli and bifidobacteria (Gibson & Roberfroid, 1995) While the former approach has been widely advocated, it is likely that a greater number of food products may have prebiotic effects. A further important objective was to confirm the effects of high-fiber cereals on fatigue, cognition and digestive functioning as assessed through the use of daily and 14-day questionnaires
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