Abstract
PurposeTo investigate whether age influences colonic polyphenol metabolism.MethodsHealthy participants, younger (n = 8; 23–43 years) and older (n = 13; 51–76 years), followed a 3-day low-polyphenol diet (LPD) and a 3-day high-polyphenol diet (HPD). Urinary phenolic acids (PA), short chain fatty acids (SCFA), pH and gas were monitored, alongside selected colonic bacteria. Human faecal in vitro fermentations of rutin with or without raftiline were used to evaluate the gut microbiota capacity in a subset of both groups.ResultsTotal urinary PA were higher in the older group after HPD compared to the younger group (1.5-fold; p = 0.04), with no difference between groups in terms of a change between diets (Δ high-low diet). While 17 PA were detected in all younger participants after HPD, a narrower range (n = 8 to 16 PA) was detected in most (n = 9/13) older participants, with lower level of benzoic acid (19-fold; p = 0.03), vanillic acid (4.5-fold; p = 0.04) but higher hippuric acid (2.7-fold; p = 0.03). Faecal SCFA concentration did not change after HPD within group, with similar differential excretion (Δ high-low diet) between groups. There were no differences between groups for faecal pH, total, faecal bacteria including Flavonifractor plautii, bifidobacteria, and bacteroides. In human in vitro faecal fermentations, seven PAs were detected in both groups after 24 h of rutin fermentation, with no quantitative and modest qualitative differences between groups. Total SCFA in faecal fermentation did not differ between groups, except for butyric acid (twofold higher in the older group; p = 0.009) when rutin was fermented with raftiline over 24 h.ConclusionsUrinary phenolic acids were less diverse in older participants despite limited difference in functional capacity of in vitro faecal fermentations.
Highlights
The number of adults aged 60 years and over will double between 2000 and 2050, from 11 to 22% [1] globally
As there are very limited data on the effect of ageing on the bacterial metabolism ofphenols, this study aimed to test whether age (≥ 50 years) affects the colonic metabolism of dietaryphenolics, with a focus on flavonols, which are ubiquitous in the Western diet
This study tested the hypothesis that age influences the metabolism of dietaryphenols, which may be relevant for gut health and the development of chronic diseases
Summary
The number of adults aged 60 years and over will double between 2000 and 2050, from 11 to 22% [1] globally. The increase in lifespan has a direct effect on the incidence of age-related diseases, including colorectal cancer (CRC), which can put a tremendous strain on health services [2]. Changes in the colonic microbiota and its metabolic products including short chain fatty acids (SCFA), butyrate, acetate and propionate, could directly affect the proliferation, differentiation, and gene expression of the colonic epithelium [4,5,6]. Butyrate is the primary energy source for colonocytes, and may play a key role in maintaining homeostasis of the colonic mucosa inhibiting proliferation and inducing apoptosis and differentiation in colorectal cancer cell lines [7, 8]. The conversion of the parent (poly)phenolic compound (poorly bioavailable) to smaller phenolic acids (with increased bioavailability) by the colonic microbiota is likely to be an important contributor to the beneficial effect ascribed to the compounds
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