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Probiotics and Prebiotics


Frst, let’s start with some definitions for those of us who are not firmly up to date on our gut microbiota (ecological communities of commensal, symbiotic and pathogenic microorganisms). And, in that vein: commensal organisms have no effect on the host upon which they live, symbiotic means that the relationship is mutually beneficial, and pathogenic means they can cause disease.

So, 100 trillion organisms live on and inside our bodies; they are there from birth and can be added to through the foods we eat. These are probiotics: foods which contain live bacteria or yeast (also a single-celled organism, like bacteria, but considered a fungi). For example, anything which is fermented (meaning a food made by converting another food through controlled bacterial growth) e.g. yoghurt, kefir, kombucha, sauerkraut, tempeh, natto, miso, kimchi, bread and pretty much all alcoholic drinks. Many of these foods are labelled as containing healthy or friendly bacteria although the quantities are not mentioned, and neither is whether the bacteria will stay alive all the way to your gut. Most of the yeast in bread will die in the baking process, but some will survive; Kvass (a Russian drink) is made by fermenting the yeast in bread again to make a very slightly alcoholic (about 1%) beverage.


Prebiotics are “compounds in food that induce the growth or activity of beneficial microorganisms such as bacteria and fungi”. They are specialised plant fibres, and are essentially the things the probiotic guys like to eat. On this list we have Artichoke, Garlic, Onions, Leeks, Asparagus, Sweet Potato, Cabbage, Apples, Berries, Bananas (particularly when less ripe), Cocoa (much better than unripe bananas), and Beans and Lentils. This list goes on but that’s plenty for now. 

There is currently an argument in the medical world about leaky gut syndrome (defined as increased intestinal permeability which allows bacteria and toxins to leak out). The debate is over whether it causes a range of problems in the body and whether it is caused by drinking too much alcohol, taking non-steroidal anti-inflammatory drugs (e.g. ibruprofen) or because the bacteria in the gut are so starved they begin to digest the lining of the gut itself. Leaky gut syndrome is claimed to cause food sensitivities, fatigue, feeling bloated and other digestive issues and skin problems. It is also argued that it may contribute to migraines, multiple sclerosis, fibromyalgia, thyroid abnormalities, mood swings, and autism.


Probiotics have been found to lower cholesterol and blood pressure when taken every day for 8 weeks. A new field of research is looking at the effects of gut bacteria on the brain. It’s called psychobiotics, and it’s finding that the metabolites of our gut microbiota stimulate the brain and affect neurotransmitters and even our DNA and its expression.  


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