First things first: Let's define these food groups. Fibre is a type of complex carbohydrate found exclusively in plants that isn't broken down in the digestive tract and, therefore, helps with satiety, digestion, blood sugar balance, healthy bowel movements and microbial balance (i.e., good versus bad gut bugs). Fibre-rich staples include buckwheat, barley, kale, broccoli, lentils, cabbage, beans, sweet potatoes and more—you can find a full list here.
Fermented foods, on the other hand, are created through fermentation (duh), in which components of foods, like the natural sugars, are broken down by yeast and bacteria and result in food chock-full of probiotics (aka, the good bugs), amino acids, polyphenols (antioxidants), bio-available vitamins and minerals.
Some examples include water and milk kefir, kombucha, kimchi, kraut, miso, and live yogurt.
Beware of so many products that have been pasteurised to kill off the live bacteria to create a long shelf life, have added sugar or sweeteners such as erythritol, sorbitol, sucralose, saccharin, aspartame. I have recently looked at many of our competitors and shocked at the additives.
To boil it all down to a one-sentence comparison: Fibre foods feed the good bugs in your gut, while fermented foods help increase the actual number of those good bugs.
Howeverrrrr ... these wonderful good bacteria digest the fibre and resistant starch, releasing energy producing carbohydrates, amino acids (the essential building blocks of protein), and polyphenols (antioxidants), vitamins and minerals.
Both are ultimately important for optimal gut health, and one is not necessarily "better" than the other. However, if you're just embarking on your gut health journey, its important to get your fill of fermented foods before loading up on fibre.
In a recent study undertaken by Harvard Medical School, in which researchers measured microbial diversity in folks who ate five to eight servings of fibre per day versus those who ate six cups of fermented foods per day: "What they found is that a high-fermented-foods diet increased microbial diversity in that group and lowered 19 inflammatory markers," he explains.
What are the best foods for gut health? Fibre and fermented foods, as both are ultimately necessary for a flourishing microbiome. However, if you already have an unhealthy, inflamed gut, you might want to especially load up on fermented foods. Once you replenish those healthy gut bacteria, then you might feel more comfortable feeding them with fibre to do just that.