The human microbiome refers to all the microorganisms that live in or on humans. These include the likes of single-celled organisms, fungi, non-living viruses, and most prominently, bacteria. In fact, we have more bacterial cells in our bodies than human cells, with estimates of the ratio ranging from 3:1 to as much as 10:1. Our microbiomes are extremely important to our overall health, providing us with abilities our human cells cannot, such as digesting certain foods, or fighting off harmful bacteria.
Some estimates say that our microbiomes represent about 80% of our immune systems. The vast majority of these microorganisms are found in the gut, but can also be found in other open cavities, such as the nose or genitals. Apart from the fact that what we eat gives us certain nutrients, vitamins, etc, the fact that so much of our immune systems are in the digestive tract is one of the reasons that things like genetically modified food and the use of certain pesticides have remained controversial for so long: many people argue that what goes into our food ultimately ends up affecting our immune systems directly.
Before looking at the differences between probiotics and prebiotics, it is worth discussing antibiotics in the context of the human microbiome. While antibiotics have undoubtedly saved millions of lives, we in society have started to treat them very casually. Most doctors who prescribe antibiotics will tell you that the first question they hear is whether or not they will affect drinking, not immune systems. But antibiotics work by essentially flushing out the microbiome and starting it anew, which replaces all of the microorganisms involved. Studies have now shown that this can affect your immune system and make you more susceptible to developing certain health issues. As science advances, antibiotics are becoming more targeted, but drastically changing your immune system is not something to be taken lightly, so make sure to discuss this with your doctor if you are considering antibiotics.
On the other hand, probiotics and prebiotics are both beneficial for your microbiome, but each has a very different purpose. Probiotics tend to come as either an added ingredient in food, quite commonly yoghurt, and contain live bacteria. These are the so-called “good bacteria” that we hear about in advertisements. Prebiotics on the other hand are a form of non-digestible fibre. Bananas, onions, and raw garlic are all examples of food that are high in prebiotic fibres. When prebiotics are ingested, they move past the small intestine and settle in the colon, where they are fermented. This is essentially fertiliser or feed for the bacteria that exists in your gut already, whether that is naturally occuring or from probiotics. The purpose of prebiotics is to encourage the growth of the good bacteria.
As mentioned earlier, your microbiome plays an enormous role in your overall immune system, so keeping it healthy is very important. Probiotics and prebiotics are often used in treating conditions like Irritable Bowel Syndrome or diarrhea, but their benefits extend far beyond that. While they may not be as influential in treating conditions like depression and anxiety as previously suggested, both are very beneficial to your immune system, and therefore your overall health and quality of life.