5.1 Prebiotics and probiotics

One way in which the health of the gut microbiome can be improved is through the use of prebiotics and probiotics. Although these have similar names, they contain quite different substances designed to improve the health of the gut microbiome.

Prebiotics act as a food source for the beneficial bacteria in the gut microbiome and help those bacteria to thrive in order to improve the balance of bacteria within the microbiome. Prebiotics are typically substances that cannot be broken down by human enzymes, that can withstand the acidic environment of the stomach, and which are not absorbed in the upper GI tract.

Prebiotics are typically complex carbohydrates, and can be found naturally in high quantities in lots of different food sources, but especially:

• legumes, beans, and peas
• oats
• bananas
• berries
• Jerusalem artichokes (not the same as regular artichokes)
• asparagus
• dandelion greens
• garlic
• leeks
• onions.

In contrast, probiotics are a collection of live, beneficial microorganisms, often bacteria or yeasts, that are ingested with the aim of colonising the gut to improve the quality and diversity of the gut microbiota. Probiotic bacteria are found in fermented foods, such as live yoghurt, kimchi, sauerkraut, and pickled vegetables, but there are many other commercial mixtures and dietary supplements available too, such as probiotic yoghurt drinks and kefir.

Figure 30 Prebiotic and probiotic foods. The cartoon figures represent the microorganisms in the microbiota that use the pre- and probiotics to thrive and replicate. The tablets represent probiotic supplements (dried or desiccated bacteria products)

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A cartoon-style illustration depicts prebiotic and probiotic foods. Probiotics include supplements in capsule form, milk, flavoured yoghurt, and cottage cheese containing microbiota. Prebiotics include a bunch of red grapes, tomatoes, green apple, zucchini, peas, and broccoli containing microbiota.

Figure 30 Prebiotic and probiotic foods. The cartoon figures represent the microorganisms in the microbiota that use the pre- and ...

Pharmaceutical-grade probiotics, which contain very high amounts of microorganisms, have been shown to have some benefit in clinical trials (NHS, 2022). The high number of microorganisms in pharmaceutical-grade probiotics is thought to result in some of the bacteria being able to survive the highly acidic stomach and beyond. The benefits of commercially-bought probiotic supplements are still controversial, as they contain low concentrations of the microorganisms, the majority of which will most likely be destroyed by the highly acidic environment of the stomach. However, there is still some anecdotal evidence (i.e. not scientific, based on personal accounts) that these may provide some benefit in specific intestinal disorders. To date, there has been no scientific evidence to indicate that there is any benefit to healthy individuals taking probiotics (Jabr, 2017).

You are going to finish off this OpenLearn course by learning about a slightly less palatable way to improve the health of the gut microbiome – faecal transplant!