12 January - 20 June 2016

The impact of polyphenols on gut microbiota

11 Sept 13

Polyphenols have been associated with a number of health benefits including cardiovascular function, blood pressure and plasma lipid profile amongst others.  A study published in the journal Food Research International led by Kemperman from Unilever R&D, has investigated the impact of polyphenols from black tea and red wine grape extract (RWGE) on a gut microbial community.  After ingestion, some polyphenolic compounds are absorbed by the gut epithelium while the majority pass to the large intestine and are metabolised by colonic microbiota.  As the majority reach the lower intestinal tract, a mechanism of action most likely involving an interaction with the microbiota present with some bacterial groups transform polyphenols into metabolites which enhance the low systemic bioavailability of the native compounds.    Using an in vitro simulator of the intestinal microbial ecosystem (SHIME) model, complex dietary polyphenols from black tea or red wine grape extract on colonic microbiota were investigated.   The RWGE contained 80% polyphenols of which 13% were identified as anthocyanins (9%), cathechin and procyanidin di/trimers (3%).   The tea extract contained 5% caffeine and 44% total polyphenols of which 4% were catechins , 2% flavonols, 2% gallic acid and 0.5% theaflavins. Both black tea extract and RWGE resulted in inhibition of bacterial growth leading to the presence of fewer species and a reduction in bacterial numbers. These effects were observed even after a single dose (1000 mg polyphenols) and after a 2 week continuous period (1000 mg/day administered 3 x daily). The antimicrobial effects of the polyphenols were selective and some bacterial groups appeared to be stimulated in the presence of polyphenols.  Black tea stimulated Klebsiella, enterococci and Akkermansia and reduced bifidobacteria, B. coccoides, Anaeroglobus and Victivallis. RWGE promoted growth of Klebsiella, Alistipes, Cloacibacillus, Victivallis and Akkermansia while bifidobacteria, B. coccoides, Anaeroglobus, Subdoligranulum and Bacteroides were decreased.  The polyphenol intervention showed a reduced Firmicutes:Bacteroidetes ratio.  Obesity has been suggested to be associated with a higher ratio which is normalised during weight loss.  It has been hypothesised that a diet high in polyphenols and low in probiotics might support maintaining normal body weight in obese individuals but this needs further validation.  Polyphenol administration also led to a decrease in ammonium production which may be considered to be a positive effect as ammonium is an indicator for proteolytic conditions which are usually associated with increased toxicity and tumorigenesis.  Kemperman et al note that the effect on gut microbiota compositon in vivo can be expected to be less severe as interaction with other dietary components may reduce the levels of polyphenols available to the gut microbiota and so further investigation in vivo is needed.

A mouse study published in Science by Gordon et al has investigated the intimate ties between gut bacteria and diet in the development of obesity. The researchers bred mice in a sterile environment so they had no gut microbes of their own. Gut microbes from human twins - where one twin was lean and the other obese, were then transplanted into the mice. The mice receiving the obesity-related gut microbes gained weight and fat, and developed obesity-related metabolic problems, while the mice that received the leanness-related gut microbes did not. Gordon et al. then paired up the mice so that the ones with microbes from the lean human twin were put in the same cages as mice with gut microbes from the obese twin.  Mice naturally eat each other's faeces, so when the lean and obese mice were caged together, the scientists found that their guts were invaded by Bacteroidetes bacteria from the mice carrying the leanness-related gut microbes. Bacteroidetes are efficient at harvesting calories and nutrients from food.

RSSL's Functional Ingredients Laboratory can assay a range of products for polyphenolic components. For more information please contact Customer Services on Freephone 0800 243482 or email enquiries@rssl.com

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