What is the gut microbiota?
The gut microbiota is the layer of so called “friendly” bacteria that line (called the flora) our digestive systems. Each person has a unique mixture of different varieties of bacteria (from Firmicutes to Lactobacillus and many more) which we which we collect over our lifetime. We acquire some from our mother’s placenta at birth, and then over our lifetime from the food and drinks we eat and our environment.
The gut flora microbes have a beneficial role in health. They provide a protective barrier between the walls of our intestines and stomach and our digestive system, protecting us from inflammation from when a pathogenic, or disease causing, microbe tries to invade our gut. They also regulate our immune system, reducing food allergies and intolerances by reducing the immune system hyper-sensitive response (when our bodies infection-protective-defence mechanisms see something non-disease causing like milk or nuts as disease causing) via control of immune cells called T regulatory cells.
They also work via the brain-gut axis to help regulate Serotonin, the happiness neurotransmitter (brain chemical) and hormone, and Dopamine, the pleasure and reward neurotransmitter and hormone, and so play a role in mental health and focus and concentration. Recent evidence even shows that they help regulate cholesterol levels and the glycaemic index of foods, and so play a role in metabolism, weight, and insulin regulation (how we respond to fats and carbohydrate sugars in our diet).
What to eat to improve your gut health?
Probiotics
Probiotics are products which have been specifically formulated to include specific classes of micro-organisms which have a benefit to health. These products, including natural sources like natural yoghurt or kefir, or supplemented products like some types of yoghurt drink products and medications, directly add helpful bacteria to your gut. The ideal is to add some strains of Lactobacilli and Bifidobacterium, Saccharomyces boulardii and Bacillus coagulans to your gut, as well as some helpful E. coli strains.
Probiotics are not regulated, and so be sure to research the bacterial strains included before you purchase a product. Many of the “gut friendly” yoghurts contain high levels of sugars and so try to find one with less than 10g of sugar per serving (120ml/g serving size). Also avoid anything pickled in vinegar as, despite the marketing, vinegar is a preservative designed to kill micro-organisms, including helpful bacteria, and so there will be little or no probiotic benefit to the product.
Examples of probiotics include:
- Natural yoghurts
- Greek yoghurt
- Fortified yoghurt drinks and yoghurts
- Kefir
- Kombucha
- Sauerkraut
- Miso and other soy products
- Sourdough
- Kimchi
- Pickles (those not pickled in vinegar as this kills bacteria)
Prebiotics
Whilst the probiotics add gut microbes to the gut, the prebiotics feed existing gut microbes, helping to increase their numbers and increase their health and health-giving properties for us. A prebiotic is a type of fibre, although this does not mean all fibre is prebiotic.
There are two types of prebiotic fibre:
- Soluble: This absorbs water and binds to the carbohydrates and sugars in food and slows their digestion, so improves their glycaemic index, helping to keep your energy levels balanced and you feeling fuller for longer (as energy dips increase appetite). These include oats, psyllium husk, barley, beans, lentils, and the pectin found in most fruit (mainly citrus fruit) and peels.
- Insoluble fibre: This is the roughage that improves digestive health. It is found in wholegrains in bread and wholegrain pasta, wild rice, quinoa, buckwheat, nuts and seeds and vegetable (such as carrot, parsnips, onion, potato, and apple) skins and peels.
Both types of fibre increase the numbers and benefits of the gut flora.
Other things you can do to increase the gut microbiota
The gut microbiota love prebiotics, and the main prebiotic is fibre. Most fibre is found in the skins and peels of vegetables and so, to reduce food waste and carbon emissions from landfill of food waste, AND boost your healthy gut flora, the best option is to stop peeling your carrots and to eat your potato skins. Broccoli stems and cauliflower leaves are also thrown away by most households but are super high in prebiotic fibre and vitamins. Feed your gut and stop throwing away fabulous fibre.
References
- Cheng, L., Kong, L., Xia, C., Zeng, X., Wu, Z., Guo, Y. and Pan, D., 2022. Sources, Processing-Related Transformation, and Gut Axis Regulation of Conventional and Potential Prebiotics. Journal of Agricultural and Food Chemistry.
- Manning, T.S. and Gibson, G.R., 2004. Prebiotics. Best practice & research clinical gastroenterology, 18(2), pp.287-298.
- Pimentel, T.C., de Assis, B.B.T., dos Santos Rocha, C., Marcolino, V.A., Rosset, M. and Magnani, M., 2022. Prebiotics in non-dairy products: Technological and physiological functionality, challenges, and perspectives. Food Bioscience, p.101585.
- Puntillo, M., Segli, F., Champagne, C.P., Raymond, Y. and Vinderola, G., 2022. Functional Microbes and Their Incorporation into Foods and Food Supplements: Probiotics and Postbiotics. Annual Review of Food Science and Technology, 13, pp.385-407.
- Williams, N.T., 2010. Probiotics. American Journal of Health-System Pharmacy, 67(6), pp.449-458.