Why are polyphenols so important for health?

If you were to ask us why the consumption of fruits, vegetables and nuts has always been considered recommended, surely the words “vitamins” and “minerals” would be the first that would come to mind. But what about polyphenols? Have we ever heard of them?
Polyphenols: what they are and where they are
Polyphenols are secondary metabolites that plants produce as a defense when exposed to stressful situations such as ultraviolet radiation or fungal infections.
They are present in foods of vegetable origin such as fruits and vegetables, nuts, olive oil or wine, where among other things, they provide color, smell and bitterness. But beyond providing organoleptic characteristics to food, different studies have shown that the administration of polyphenols produces beneficial effects in humans. In fact, the efficacy of polyphenols in improving markers of metabolic diseases such as diabetes and insulin resistance, cardiovascular disease, or certain types of cancer has been described.
That would explain why dietary patterns characterized by a high content of foods rich in polyphenols, such as the Mediterranean diet, are related to an improvement in the general state of health. In this sense, although the simplest and most accessible way to ensure the intake of polyphenols would be through the consumption of the aforementioned foods, there is an increasing trend towards the use of supplements with polyphenols.
However, and despite the beneficial effects described for polyphenols, their effectiveness may be limited due to the metabolization they undergo in the intestine. This would make the amount of polyphenols that reach the organs and tissues much less than what is ingested. The good news is that more and more research suggests that this limitation of polyphenols may not be so much.
Polyphenols and microbiota: friends or foes?
In recent years, more and more attention is paid to the intestinal microbiota due to the important role it plays in important biological processes. These include immune function, the production of bioactive metabolites and the digestion of certain food components.
Its functionality depends mainly on its composition and, in turn, this is conditioned (among other factors) by the diet of the host. For example, adherence to the Mediterranean diet has been seen to contribute to an increase in the abundance of bacterial species considered beneficial, such as Bifidobacterium animalis, Oscillibacter valericigenes and Roseburia faecis.
On the other hand, the current Western eating pattern, rich in saturated fats and sugar, is related to an altered composition of the microbiota (less diverse), which seems to be involved in the development of inflammatory metabolic diseases such as obesity or diabetes.
In the case of polyphenols, it has been suggested that the metabolization they undergo by the intestinal microbiota results in a prebiotic effect.
On the one hand, secondary metabolites of polyphenols with anti-inflammatory properties are generated. On the other hand, there are changes in the composition of the microbiota, increasing its diversity and favoring the generation of microbial metabolites with anti-inflammatory effect, such as short-chain fatty acids.
All this ends up reducing inflammation of the intestine, which will help maintain the function of intestinal barrier and reduce the number of pro-inflammatory mediators that reach the bloodstream (which produce metabolic alterations in different organs and tissues).
In addition, numerous studies indicate that polyphenols also inhibit pro-inflammatory mediator synthesis pathways and increase the expression of tight-binding proteins in enterocytes, helping to reduce intestinal permeability.
It has also been proposed that they could contribute to the secretion of mucin and slow down the synthesis of reactive oxygen species (ROS).
All this would favor the creation of an optimal environment for the growth of bacteria considered beneficial such as Akkermansia muciniphila. It should be noted that such effects have been described both for polyphenol supplements and for dietary patterns containing foods rich in polyphenols.
In summary, the available scientific evidence indicates that polyphenols could exert effects similar to those of prebiotics in terms of the intestinal microbiota.
In In this sense, the intake of polyphenols would regulate the composition of the microbiota and its functionality. It follows that consuming foods rich in polyphenols could be an effective strategy for maintaining a healthy microbiota. All this without forgetting that certain factors, such as genetics or the lifestyle of an individual, can influence both the health of the intestinal microbiota and the potential effects that the consumption of polyphenols can produce.
Iñaki Milton Laskibar, Postdoctoral Researcher at Cardiometabolic Nutrition Group, IMDEA Alimentación. Researcher at Centro de Investigación Biomédica en Red de la Fisiopatología de la Obesidad y Nutrición (CiberObn), University of the Basque Country / Euskal Herriko Unibertsitatea; Laura Isabel Arellano García, Nutrition and Health Student, University of the Basque Country / Euskal Herriko Unibertsitatea and Maria Puy Portillo, Professor of Nutrition. Network Biomedical Research Centre for the Pathophysiology of Obesity and Nutrition (CIBERobn), University of the Basque Country / Euskal Herriko Unibertsitatea
This article was originally published on The Conversation. Read the original.

Original source in Spanish