Certain lifestyle factors, illnesses and overuse of antibiotics are implicated in the destruction of good bacteria in the gut, a reduced diversity of species, and a subsequent imbalance. This is a relatively new area of scientific inquiry, but early research suggests that dietary manipulation with probiotics and prebiotics could help prevent or repair this damage.
Probiotic foods help to reintroduce some species into the population (microbiota), whereas prebiotics feed the existing bacteria, helping them to grow and multiply. These foods contain special elements enabling them to survive the journey through the digestive system.
All probiotic foods are fermented foods, but not all fermented foods are probiotic. To be classed as a probiotic, a food must contain strains of beneficial LIVE bacteria when we consume it. Despite many fermented foods starting out with probiotic potential, all that beneficial bacteria can die if the product is subjected to inhospitable environmental conditions such as being heat-treated during processing or stored in the wrong manner. Most probiotic foods require cool temperatures to remain viable.
The most common probiotic foods are vegetables naturally fermented with salt (such as sauerkraut or kimchi) and fermented full-cream milk products (yoghurt, kefir). There is no evidence to support probiotic claims for apple cider vinegar or fermented tea (kombucha), but these foods may provide other benefits.
Prebiotic foods feed and nourish the beneficial bacteria living in our gut. These foods contain a specific type of carbohydrate, an indigestible dietary fibre capable of travelling the length of the gastrointestinal tract (GIT) without being absorbed into the bloodstream. Obesity studies are reporting reduced inflammation and oxidative stress in the liver, increased production of gut hormones, reduced appetite in the brain’s control centre, and a reduction in growth of fat cells – which sounds very promising for anyone struggling to lose weight.
Foods known to possess a prebiotic function include a range of vegetables, fruit and grains capable of feeding both the host body and the gut bacteria:
- Vegetables (asparagus, beetroot, savoy cabbage, onion, leek, shallots, spring onion, green peas, snow peas, chicory, garlic, fennel bulb, sweet corn, and the potato-like Jerusalem artichoke that is a species of sunflower;
- Legumes (baked beans, chickpeas, lentils, soybeans, red kidney beans);
- Fresh fruit (watermelon, grapefruit, bananas, nectarines, white peaches, custard apples, persimmon, tamarillo, rambutan, pomegranate);
- Dried fruit (dates, figs);
- Breads and cereals (oats, barley, rye bread, rye crackers, pasta, gnocchi, couscous, wheat bran);
- Nuts and seeds (cashews, pistachio nuts).
Healthy human intestines play host to more than 1000 strains of microscopic good bacteria and we are discovering how important they are in keeping us healthy. Our gut microbes help produce folate, short-chain fatty acids (SCFA), and crucial neurotransmitters such as serotonin and gamma amino butyric acid (GABA) that are necessary for healthy brain and nervous system function. We can serve and protect these little champions by feeding them the right food.
- Cani, P. D. (2018). Human gut microbiome: Hopes, threats and promises. Gut, 67(9), 1716–1725.
- Kovatcheva-Datchary, P., & Arora, T. (2013). Nutrition, the gut microbiome and the metabolic syndrome. Best Practice and Research: Clinical Gastroenterology, 27(1), 59–72.
- Monash University. (2019). Prebiotic diet – FAQs – Department of Gastroenterology. Retrieved September 11, 2019, from https://www.monash.edu/medicine/ccs/gastroenterology/prebiotic/faq
- Rezac, S., Kok, C. R., Heermann, M., & Hutkins, R. (2018). Fermented foods as a dietary source of live organisms. Frontiers in Microbiology, 9(AUG).