Polyphenols, plant compounds present in large amounts in tea, orange juice or dark chocolate, feed the bacteria that defend the intestinal barrier and reduce inflammation in the elderly.
When we eat, the food we eat goes through a process of decomposition to be converted into energy. In the stomach, gastric juices break down food into simpler molecules that reach the small intestine and from there pass into the blood. However, the second part of digestion takes place in the large intestine: colonies of trillions of bacteria, viruses and fungi that together are called the microbiota.
The microbiota microorganisms are responsible for processing those molecules that our body cannot digest on its own. In the process, these bacteria produce different metabolites, substances that, among other things, reinforce the intestinal barrier and reduce inflammation. One of these protective metabolites is called indole-3-propionic acid (IPA).
A new study, published in Molecular Nutrition Magazine and Food Research in charge of Biomarkers and Nutritional Metabolomics of Food Research Group at the University of Barcelonashows that consumption of polyphenols, plant-based compounds present in dark chocolate or green tea, modifies the microbiota, causing colonies of IPA-producing bacteria to increase.
“IPA is a curious metabolite because all the functions discovered in it are beneficial,” says Tomás Meroño, co-author of this study and a biochemist. IPA protects the intestinal barrier, has metabolic and brain effects. “In research with obese children, lower IPA production was associated with lower scores on memory tests,” he adds.
For eight weeks, the study carried out by the Network Center for Biomedical Research in Frailty and Healthy Aging (CIBERFES) observed the consumption of polyphenols in 51 people over 65 years of age in a geriatric home in Italy. While some continued their usual diet, the polyphenol-rich diet group ate lunch and snacks on polyphenol-rich foods such as blueberries, orange or pomegranate juice, green tea, applesauce or dark chocolate.
“These dietary adaptations are viable because they are small interventions, accessible to the palate and adaptable to the peculiarities of the elderly population, such as being easy to chew and swallow”, explains the UB scientist. Feces and blood serum were then analyzed.
In addition to increasing the concentration of IPA, the diet rich in polyphenols improved the levels of zonulin, a marker of intestinal permeability. If the permeability is lower, less toxins are absorbed, which can cause inflammation in the gut. “So, if a diet rich in polyphenols decreases permeability, it can be beneficial for healthy aging,” explains Meroño.
In the study, no differences were observed between ages or between men and women, but the effect of the polyphenol-rich diet varied in the 18 people with kidney disease. “By separating the data between patients with kidney disease and without disease, we saw the research results because people with kidney disease didn’t increase their IPA, it stayed the same,” says Meroño.
There are studies that indicate that kidney disease alters the composition of the microbiota, and since IPA is a metabolite that depends on the microbiota, the UB researchers think that this microbiota is so altered that it can no longer be modified with this strategy.
Can the function of the microbiota be altered?
In this test, the consumption of polyphenols modified the function of the microbiota, which in turn helped to increase the IPA. In addition to diet, lifestyle, physical exercise, alcohol consumption and health status influence the composition and therefore the functions of the microbiota.
During the study they found bacteria that were associated with positive changes, but Meroño believes that composition is not as important as function. For example, “when you eat fiber, you are feeding beneficial bacteria, and their growth leads to improved function,” he explains.
And the polyphenols?
Plants produce polyphenols in response to stress due to changes in temperature, light, infections, or lack of water. Polyphenols are found in foods such as vegetables, fruits, vegetables, olive oil, green tea or dark chocolate. These compounds have been associated with a lower risk of cognitive decline, increased bone mineral mass, a lower risk of cardiovascular disease and a lower risk of diabetes, but so far it has not been fully explained why they were beneficial.
In general, polyphenols are considered prebiotics because they favor the growth of bacteria and, at the same time, modify their function, as in this case. In addition to all these qualities, Meroño highlights the relationship they have with sustainability and local food that pollutes less. “There is a hypothesis called xenohormesis that suggests that foods grown near your region have a more health-beneficial amount of polyphenols than foods grown elsewhere,” explains Meroño. This is because southern hemisphere foods were grown under different conditions than northern foods, so the amount of polyphenols likely varies depending on where it was grown.
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