The health benefits of antioxidants are widely known. In particular, their ability to prevent free radical damage throughout the body and helping us fight off illnesses by boosting our immune systems. One of these antioxidants is polyphenols, which we get from a variety of plant-based foods. So why are we talking about them? Because they are also good for our gut!

Polyphenols have been shown to help with digestion issues, and a study published in the Journal of Nutritional Biochemistry study focused on how polyphenols can promote overall health as well as gut health.

Polyphenols and the Gut

This study examined the reciprocal interactions between the gut microbes and polyphenols, including the benefits on human health. One thing is certain – there is a dietary polyphenol influence on the modulation of the composition or activity of the microbes in our gut.

When we talk about dietary polyphenols, we are referring to natural compounds found in some fruits and vegetables, but also in legumes and nuts, coffee and tea, chocolate, and even wine.

Once ingested, our body treats them as a foreign substance and much like prebiotic fiber, they are able to pass through the stomach and into the small and large intestines relatively undigested. Intestinal microbes then break down the polyphenolic structures into the nutrients that are responsible for the health benefits.

This polyphenol-microbiota relationship, according to studies, can affect the gut bacteria and change the composition of the microbiota in beneficial ways. Thus, polyphenols can help us keep our gut microbiota in balance. Polyphenols can also provide protection against gastrointestinal disorders and pathogens, enhance the nutrient processing, reduce cholesterol, and reinforce the immune system.

The study also suggests that polyphenols have anti-inflammatory, anticarcinogenic, antidiabetic, antiadipogenic, and neuroprotective properties in addition to their antioxidant properties. The consumption of polyphenol-rich foods can reduce the risk of a number of serious chronic diseases like diabetes.

Effects of Polyphenols on the Gut: Modulation of the Microbial System 

Human research trials concluded that differences in individual gut microbiota populations led to differences in the bioavailability and bioefficiency of polyphenols and their metabolites. Certain doses of selected polyphenols were shown to modify the microbiota composition. While some bacteria remain inhibited, the good ones can prosper to maintain the balance.

What really changes the microbiota composition are phenolic compounds. Specific flavan composition, even in the presence of other nutrients such as proteins and carbohydrates, can significantly prevent the growth of Clostridium histolyticum, while enhancing the growth of E. coli and members of the Clostridium coccoides–Eubacterium rectale group.

The same applies for dietary administration of extracts rich in proanthocyanidin. Research done on rats showed that a proanthocyanidin-rich extract diet derived from a dealcoholized red wine made a shift in the predominance of Bacteroides, Clostridium and Propionibacterium spp. to prevalence of Bacteroides, Lactobacillus and Bifidobacterium spp.

Another study on proanthocyanidin-rich extracts from grapes demonstrated a similar increase in bifidobacteria, a group of bacteria living in intestines and preventing a wide range of disorders. The same results can be obtained from dietary extracts from sources like chocolate, green tea, and blackcurrant or grape seeds. All can modulate the intestinal microbiota and make positive changes in the beneficial bacteria. Additionally, the tea phenolic reduces the growth of pathogenic bacteria while the polyphenol found in the wild blueberry has an important modulating role on the gut microbiota composition.

All of these polyphenol food groups have a major impact on our digestive track, as they support healthy bacteria which leads to a stronger immune system and disease prevention.

Polyphenols, Microbes and Cancer   

Several studies have seen a connection between gut health, polyphenols, and colorectal cancer prevention. Studies done on rats demonstrated that certain nutrients can be converted by the gut microbiota into positive compounds that decreased the tumor number and size and cancerous cell multiplication while also increasing tumor cell apoptosis (the death of cells that occurs as a normal and controlled part of an organism).     

Moreover, some polyphenol dietary components may in fact lower the overall risk of cancer, by affecting the colonic mucosal enzymes and bacterial enzymes that are associated with a significant reduction of the rate at which colonic tumors occur.

Another element to consider for the extra health security is ellagic acid, which is packed with a multitude of biological properties like antioxidant and cancer preventing activities. Coffee and caffeic acid specifically inhibited colon cancer metastasis and neoplastic cell transformation (abnormal growth of tissue) in mice.

Other Health Benefits of Polyphenols

We have noted the benefits of polyphenol-rich foods, but let’s pay some attention to their impact on the immune system and intestinal health. Red wine polyphenols have a protective aspect with regards to cardiovascular and circulatory function because they can decrease blood pressure, cholesterol, and inflammation.

Fruit, green tea, and wine vinegars can help with healthy weight maintenance and weight loss, and in clinical trials on human subjects classified as having anxiety issues who consumed dark chocolate resulted in a major positive modification in the metabolism.

Interestingly, upon closer inspection of proanthocyanidins polyphenols, it has been suggested that they just might be a new beneficial therapy for the management of immunoinflammatory diseases like atherosclerosis, as well as for reducing inflammatory response to bacterial agents such as those experienced in chronic inflammatory or autoimmune diseases like IBD.

Adding to the equation, microbial metabolites of plant polyphenols can also decrease the risk of metabolic syndrome; the polyphenol properties of ellagitannin are very important when it comes to diabetes and related diseases, including blindness.

All in all, most of the studies confirm that not only the food polyphenols, but their microbial metabolites, must be taken into account when talking about the number of benefits they have on our overall health.

Anyone can certainly benefit from taking steps to get more natural food-based polyphenols in their diet. Best of all – a lot of those foods also contain prebiotic fiber, to pack and even bigger punch to both gut and overall health.