Dietary fibres and IBS: translating functional characteristics to clinical value in the era of personalised medicine

Abstract

Clinical guidelines in the use of fibre supplementation for patients with IBS provide one-size-fits-all advice, which has limited value. This narrative review addresses data and concepts around the functional characteristics of fibre and subsequent physiological responses induced in patients with IBS with a view to exploring the application of such knowledge to the precision use of fibre supplements. The key findings are that first, individual fibres elicit highly distinct physiological responses that are associated with their functional characteristics rather than solubility. Second, the current evidence has focused on the use of fibres as a monotherapy for IBS symptoms overall without attempting to exploit these functional characteristics to elicit specific, symptom-targeted effects, or to use fibre types as adjunctive therapies. Personalisation of fibre therapies can therefore target several therapeutic goals. Proposed goals include achieving normalisation of bowel habit, modulation of gut microbiota function towards health and correction of microbial effects of other dietary therapies. To put into perspective, bulking fibres that are minimally fermented can offer utility in modulating indices of bowel habit; slowly fermented fibres may enhance the activities of the gut microbiota; and the combination of both fibres may potentially offer both benefits while optimising the activities of the microbiota throughout the different regions of the colon. In conclusion, understanding the GI responses to specific fibres, particularly in relation to the physiology of the individual, will be the future for personalising fibre therapy for enhancing the personalised management of patients with IBS.

Evaluating tolerability of resistant starch 2, alone and in combination with minimally fermented fibre for patients with irritable bowel syndrome: a pilot randomised controlled cross-over trial

“…The overall tolerability of RS2 and sugarcane bagasse in combination, despite the high fibre dose of 30 g/d above background intake and the greater tendency of the minimally fermented sugarcane bagasse to induce symptoms alone, was impressive. This might relate to a synergy between fermentable and minimally fermented fibres that has previously been observed in rats, pigs and humans, where fermentation of the RS2 is distributed throughout the colon rather than predominantly proximally ( 9 ) .…”

“…The presence of sugarcane bagasse in the observed exacerbations suggests that there may be underlying mechanisms related to the fibre, independent of fermentation, that may have induced these responses, such as increases in colonic volume through its bulking actions ( 9 ) . Comparatively, tolerance of RS2 in the IBS cohort was good with no clear dose-response effects identified, even at the highest dose evaluated (20 g/d RS in addition to 20–25 g/d background total fibre intake), although there was evidence of increased bloating.…”

“…Notably, the individuals with IBS had much lower intakes of FODMAPs than a typical Australian intake and were more consistent with a low FODMAP diet ( 18 ) and baseline symptoms were lower compared with FODMAP-naïve patients ( 18 ) , which may have assisted tolerability to the fibre doses evaluated. Thirdly, the short washout between fibres evaluated may have enhanced tolerability of subsequent interventions as has been suggested with up-titration and a gradual introduction ( 9 ) , although these effects may have been attenuated by the randomised order of interventions. Finally, statistical analyses were limited by the small patient numbers evaluated.…”

“…A specific variety of type 2 resistant starch (RS2), Hi-Maize 1043, appears to be especially suitable for patients with IBS, having been shown to be fermented at a slow rate ( 7 ) . Moreover, evidence from healthy controls and animal models suggests that the fermentative activities of RS2 may be enhanced in combination with a ‘carrier’ fibre, enabling its fermentation to be more evenly spread through the colon, potentially ameliorating protein fermentation that is predominant distally ( 9 ) . Wheat bran has been previously used as the ‘carrier’, but this would be counterintuitive given its effects with IBS (as earlier).…”

The Role of Diet and Gut Microbiota in Regulating Gastrointestinal and Inflammatory Disease

“…For example, a positive correlation between gut transit time and microbiome alpha diversity was observed in healthy individuals, with increased abundance of Akkermansia muciniphilia in those considered to have longer transit time (> 59 hours) ( 201 ). Although acute consumption of non-fermentable fibres may hasten transit time, it remains unclear if this may result in long-term changes to the gut microbiota and if this alters immune homeostasis ( 202 ).…”