How Polyphenols Can Have an Effect on Cardio Disease

Polyphenols and gut microbiota

You may have heard that polyphenols are beneficial to our health, but did you know how important the gut microbiota are for this?

Polyphenols are non-nutrient bioactives found in fruits, vegetables, cocoa, teas and other plant based foods that have been linked to improvement of digestion, brain function, and blood sugar levels, as well as protection against blood clots, heart disease, and certain cancers. The polyphenols can act as antioxidants to fight free radicals and decrease or prevent inflammation, which contributes to number of the previously mentioned diseases, but the exact mechanisms of how they work is still unknown.

Some of the polyphenols are themselves broken down and metabolised by gut microbiota into more (or less) bioactive compounds, and within the human population some of us are more efficient metabolisers than others, partly because of the types of microbiota in our gut. Polyphenols can also have anti-microbial properties that can act in the gut and decrease abundance of undesirable bacteria and with that reduce the risk of disease.

There are several types of polyphenols that are classified based on their chemical structure and function. One of the classes are anthocyanins, which give red and purple colour to foods like blueberries, blackberries, blackcurrants, cherries, black rice or red cabbage. In science, we often use plant extracts and powders to maximise the benefits of these anthocyanins, but studies show that consumption of whole foods containing these compounds might be most beneficial, as they often contain a fibre component that improves the level of absorption of these phytochemicals, as well as other non-nutrient bioactives.

A science story that continues … One interesting case where polyphenols may affect health through gut microbiota is the choline-TMAO story. TMAO (or a more science sounding term – trimethylamine N-oxide), is a compound that comes from the gut microbiota breakdown of dietary choline, which is a nutrient commonly found in animal products such as meat, fish, eggs and dairy. Recent studies showed that higher TMAO levels in blood are seen in multiple diseases, such as cardiovascular disease, chronic kidney disease, inflammation and neurodegenerative disorders. This, however, does not necessarily mean that TMAO is causing disease.

Nevertheless, scientists have tried to come up with strategies to change the plasma levels of TMAO in order to test just that, and one way to do it is to change the composition of our gut microbiota. Since the choline is broken down (metabolised) by gut bacteria, researchers are trying to identify the main bacterial species involved the process and while doing this they found out that choline is first broken down to a compound called trimethylamine (TMA) in the gut, which is then converted to TMAO in the liver.

So, in order to reduce TMAO in plasma they are now focussed on reducing TMA in the gut by changing the gut microbiota. They are doing this by using different polyphenols and specifically anthocyanins to see if there is the potential to alter the gut microbiota with these polyphenols to reduce those bacteria that can use choline to produce TMA.