A polyphenol-rich diet prevents inflammation in the elderly


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Summary: Polyphenols may reduce inflammation in the elderly by altering the gut microbiota and inducing indole-3-propionic acid production.

Source: University of Barcelona

Polyphenols in the foods we eat may prevent inflammation in older people because they alter the gut microbiota and induce the production of indole-3-propionic acid (IPA), a metabolite resulting from the breakdown of tryptophan by gut bacteria.

This study, published in Molecular nutrition and food researchwas carried out by the Research Group on Biomarkers and Nutritional & Food Metabolomics of the Faculty of Pharmacy and Food Sciences of the University of Barcelona and the CIBER on Fragility and Healthy Aging (CIBERFES).

The team, led by Professor Cristina Andrés-Lacueva from the Faculty of Pharmacy and Food Sciences at UB, is also a member of the Food Innovation Network of Catalonia (XIA).

Polyphenols and healthy aging

Polyphenols are natural compounds that are considered probiotics and that we primarily get from fruits and vegetables. Several dietary polyphenols have known antioxidant and anti-inflammatory properties and the ability to interact with bacteria present in the human gut and produce postbiotics (such as IPA), amplifying their beneficial health effects.

There is a growing body of evidence confirming that the regular intake of polyphenols in the diet can contribute to healthy aging, especially when they are part of a healthy diet such as the Mediterranean and associated with a healthy lifestyle, i.e. an inclusive regular one physical activity and, for example, without tobacco and alcohol.

The study shows that the interaction between polyphenols and gut microbiota can induce the proliferation of bacteria with the ability to synthesize beneficial metabolites such as IPA. IPA is a postbiotic with antioxidant, anti-inflammatory, and neuroprotective properties that help improve gut wall health. This compound appears to help prevent some age-related diseases.

“When we consider the beneficial effects of IPA on the gut microbiota and health in general, it is important to find reliable strategies to promote the production of this metabolite,” notes co-initial signatory of the study, Tomás Meroño, of the department for Nutrition, Food Science and Gastronomy of the UB and CIBERFES.

As part of the study, researchers performed a multiomic analysis to monitor serum IPA levels. The researchers analyzed the composition of the gut microbiota in fecal samples from fifty-one volunteers over the age of sixty-five who followed a polyphenol-rich diet (including consumption of green tea, dark chocolate, fruits such as apples, pomegranates and blueberries) for eight weeks.

Increase in IPA in the blood and growth of bacteria

The results show that the polyphenol-rich diet resulted in a significant increase in blood IPA levels, along with a decrease in inflammation levels and changes in gut bacteria from the order Bacteroidales.

This shows a range of fruits and vegetables
Polyphenols are natural compounds that are considered probiotics and that we primarily get from fruits and vegetables. The image is in the public domain

Surprisingly, the researchers did not observe the same effects in the subjects with kidney disease. This could be explained by the altered composition of their gut microbiota. These subjects had lower levels of IPA at baseline compared to the volunteers with normal kidney function.

“These results could be clinically relevant as low IPA levels have been associated with rapid decline in kidney function and chronic kidney disease,” notes Professor Cristina Andrés-Lacueva.

Therefore, a polyphenol-rich diet, including probiotic foods like green tea, dark chocolate, and some fruits like apples, pomegranates, and blueberries, might increase the production of IPA through changes in gut microbiota composition. This increase in levels of a postbiotic like IPA in the elderly could be helpful in delaying or preventing chronic diseases that affect quality of life.

The study also involved teams from the University of Milan (Italy), the Quadram Institute (UK) and the National Institute of Health and Sciences on Aging (INCRA, Italy), among other institutions.

About this diet and news from inflammation research

Author: Rosa Martinez
Source: University of Barcelona
Contact: Rosa Martínez – University of Barcelona
Picture: The image is in the public domain

See also

This shows a happy elderly man

Original research: Open access.
“A diet high in polyphenols increases the gut microbiota metabolite indole-3-propionic acid in older adults with preserved renal function” by Tomás Meroño et al. Molecular Nutrition & Food Research


A diet high in polyphenols increases the gut microbiota metabolite indole-3-propionic acid in older adults with preserved kidney function


Dietary polyphenols can alter the gut microbiota (GM) and promote the production of bioactive metabolites. Several indoles resulting from the genetically engineered metabolism of dietary tryptophan have been implicated in gut barrier integrity. Our aim is to investigate the changes in GM-derived indoles during a polyphenol-rich (PR) dietary intervention in older adults.

methods and results

Randomized, controlled, crossover study in adults ≥ 60 years living in an inpatient care facility during an 8-week PR versus control diet (n = 51). Seven GM tryptophan metabolites are measured in serum and metataxonomic analysis of GM is performed on stool samples.

Exploratory subgroup analyzes will be performed based on renal function (RF). The PR diet significantly increases serum indole-3-propionic acid (IPA) in subjects with normal RF but not in subjects with impaired RF. Other GM tryptophan metabolites are unaffected.

Comparison of baseline GM composition reveals shifts in members of the Bacteroidales order, as well as a higher frequency of Clostridiales in participants with normal RF. During the study, variations in IPA are associated with changes in C-reactive protein (β = 0.32, p = 0.010) and GM, especially in the Clostridiales (right = 0.35, p < 0.001) and enterobacteria (right = −0.15, p < 0.05) orders.


A PR diet increases serum concentrations of IPA in older adults with normal RF. Our results may be important in defining appropriate nutritional interventions for older adults.

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