Polyphenols and Gut Health
In a nutshell (pun intended!) polyphenols are natural compounds found in plants. There are many different types of polyphenols out there but basically, they are the pigment in plants that give plants their distinctive colour – and they just so happen to be extremely beneficial to human health.
Why do plants have polyphenols?
Well, in addition to providing visual appeal (if it looks pretty animals are more likely to eat it), these pigments also play a role in protecting plants from environmental stressors such as UV radiation and insect damage. The visual appeal of polyphenols is one of the things I love most about them, it makes us visually able humans happy to eat things that are colourful and pretty. There’s a lot’s of other things to love about them to though so read on.
There are LOADS of different types of polyphenols that have been identified so far (over 5000 in fact), including fruits, vegies, nuts, seeds, grains, and beverages such as tea, coffee, and, my all-time favourite cacao (you thought I was going to say wine didn’t you! 😉
Well, there are polyphenols in wine too, especially the reds of course, but go easy as too much alcohol can be a problem for gut health - different post for another day). Different types of polyphenols include flavonoids, phenolic acids, lignans, and stilbenes, among many many others.
Although there are many different types of polyphenols, they all share some common characteristics such as their antioxidant properties, which allow them to
help protect our cells from damage caused by free radicals.
Additionally, many polyphenols have anti-inflammatory, anti-cancer, and other potential health benefits, which make them an important component of a healthy diet. More about the general health benefits of polyphenols can be found in this article on The Conversation.
So how do polyphenols effect gut health?
Well, I’m glad you asked! I hope you’re ready for this!
Prebiotic effects: Some polyphenols can act as prebiotics, which means that they can “feed” beneficial gut bacteria, such as Bifidobacteria and Lactobacilli, and stimulate the growth and beneficial activity. These bacteria can produce short-chain fatty acids (SCFAs), which are important nutrients for the cells that line the colon, and also have anti-inflammatory effects.
Antimicrobial effects: Some polyphenols have antimicrobial effects, which means that they can help to kill harmful bacteria in the gut, such as pathogenic bacteria that can cause infection or dysbiosis (imbalanced gut microbiota). Some of the antimicrobial polyphenols include Epigallocatechin gallate (EGCG) (found in green tea), Quercetin, Resveratrol, Curcumin and Catechins.
Anti-inflammatory effects: Many polyphenols have anti-inflammatory properties, which can help to reduce inflammation in the gut. Chronic inflammation in the gut is associated with several diseases, such as inflammatory bowel disease (IBD) and colorectal cancer.
Regulation of gut barrier function: The gut barrier refers to the physical and functional barrier that separates the inside of the gut from the rest of the body. Polyphenols can help to maintain the integrity of the gut barrier by regulating the expression of tight junction proteins, which are involved in controlling the permeability of the gut lining, thus preventing, and treating leaky gut.
So how do I get more polyphenols in my diet?
I’m glad I pretended you asked! It’s simple, eat/drink plants, lots of them, every day! Also eat a variety of coloured plants.
Challenge for the week
Notice what colours (plants not meat) you have in your breakfast lunch and dinner – I bet you there’s plenty of white, orange, some green and a bit of red. The trick is to get lots and lots of different polyphenols in your diet. The simplest way to do this is to go for different colours. Bump up your greens and get some dark greens in your daily diet, some green tea, and cacao, aim for some purple and black polyphenols too, like black rice, black quinoa, purple carrots or purple potatoes, black tahini (yep, it’s a thing! Made from black sesame seeds), and plenty more reds other than tomato and capsicum (I’m sure you already eat those).
To sum up, the beneficial effects of polyphenols on gut health are due to their ability to modulate the gut microbiota and reduce inflammation. By promoting a healthy gut microbiota, polyphenols can contribute to overall health and wellbeing. Yay!
So, as I say to my patients (and my kids), be sure to eat a rainbow every day.
References:
(1) Romo-Vaquero M, Selma MV, García-Villalba R, et al. Targeted metabolic profiling of pomegranate polyphenols and urolithins in plasma, urine and colon tissues from colorectal cancer patients. Mol Nutr Food Res. 2017;61(11):1700228. doi: 10.1002/mnfr.201700228. PMID: 28881056.
(2) Fleschhut J, Kratzer F, Rechkemmer G, Eder K. Functional properties of coffee melanoidins: a matter of size and complexity. J Agric Food Chem. 2009;57(18):8581-8588. doi: 10.1021/jf9018785. PMID: 19708392.
(3) Sánchez-Fidalgo S, Villegas I, Aparicio-Soto M, et al. Effects of extra-virgin olive oil enriched with its own phenolic compounds on the gut microbiota of mice. Eur J Nutr. 2018;57(8):2739-2750. doi: 10.1007/s00394-017-1522-6. PMID: 28948421.
(4) Kang J, Badger TM, Ronis MJ, Wu X. Non-isoflavone phytochemicals in soy and their health effects. J Agric Food Chem. 2010;58(14):8119-8133. doi: 10.1021/jf100616d. PMID: 20550189.
(5) Su Y, Yao W, Perez-Gutierrez ON, et al. Phenolic-rich blackcurrant extract (Ribes nigrum L.) alters the composition of the gut microbiota and improves high-fat diet-induced obesity in mice. Food Funct. 2019;10(8):4138-4152. doi: 10.1039/c9fo00652a. PMID: 31259370.
(6) Khan ST, Ahad A, Afridi MS, et al. Antimicrobial potential of green tea polyphenols against clinical isolates of extended-spectrum beta-lactamase (ESBL) producing Klebsiella pneumoniae. Pak J Pharm Sci. 2019;32(6):2609-2613. PMID: 31969270.
(7) Guo Y, Xie JP, Wang Y, et al. Tea polyphenols alleviate high fat and high glucose-induced endothelial hyperpermeability by modulating gut microbiota. J Agric Food Chem. 2019;67(20):5765-5775. doi: 10.1021/acs.jafc.9b01207. PMID: 31016931.
(8) Moco S, Martin FP, Rezzi S. Metabolomics view on gut microbiome modulation by polyphenol-rich foods. J Proteome Res. 2012;11(10):4781-4790. doi: 10.1021/pr300581s. PMID: 22992073.
(9) Bai Y, Cui W, Xin Y, et al. Anthocyanins from black soybean seed coat improve the beneficial effect of green tea on high-fat-diet-induced gut dysbiosis in mice. J Agric Food Chem. 2019;67(7):1846-185
