Gut Health: Probiotics and Prebiotics

Guest blog by Vicky Ware

Probiotics and Prebiotics Explained

In the last blog on bacteria I explored what the ‘microbiome’ is and how the bacteria affect your health – it turns out there are billions of bacteria living in your intestines. The good news is, these little interlopers are actually giving you a helping hand digesting your food and play a big part in training your immune system when you’re young and keeping it on track when you’re older.

Different types of bacteria have a different effect on your immune system. As they’re in your intestines, the bacteria can only eat what you eat. Different types of food allow different types of bacteria to survive. The type of bacteria in your gut have been linked with health issues from asthma and obesity to anxiety and autism, so it’s worth considering whether you’re giving your bacterial ecosystem a fighting chance by eating foods that promote ‘good’ bacteria.

Good for Health

Many studies have highlighted the beneficial effect of probiotics on human health 1.

Eating foods containing probiotics has been shown to:

-          Reduce your chance of getting an upper respiratory tract infection (a cold)

-          help with antibiotic associated diarrhoea

-          treat Clostridium difficile infection

-          treat atopic eczema

-          treat recurrent urinary tract infections

-          improve irritable bowel syndrome symptoms

-          treat infectious diarrhoea2

-          lower cholesterol

-          improve gastrointestinal function

-          enhance immune function and

-          reduce your risk of getting colon cancer 3;4.

Companies are no longer allowed to claim probiotics ‘boost the immune system’.

Although companies in the European Union are no longer allowed to make these claims, this isn’t because scientists found probiotics don’t have an effect on the immune system but because the effects are so wide ranging experts are not sure precisely what the bacteria are doing.

However, messages about the beneficial effects of probiotics are allowed by non-commercial government bodies. In fact, five EU member states have national nutritional guidelines recommending probiotic containing foods 5.

1.       Sauerkraut

Sauerkraut is cabbage that has been fermented by bacteria. While it might not sound that delicious, it has a mild flavour and makes a great addition to meals. The bacteria that cause the fermentation are already present on the cabbage leaves – the only added ingredient is salt. Sauerkraut comes with a healthy dose of Lactobacilli, one of the strains of bacteria with the most proven health benefits 6;7.

In a study which reviewed lots of previous research it was found that regular consumption of sauerkraut resulted in lower chances of getting cancer 8. However, repeatedly eating sauerkraut may cause an upset stomach, so don’t go zero to hero on the cabbage consumption 8.

Fermented vegetables are also great because fermentation is a natural way to preserve foods. Non-natural preservatives may have a negative impact on your gut bacteria (they work by stopping bacteria growing on food, so they may prevent bacteria growing in your gut).

2.       Kombucha Tea

Kombucha is made by fermenting sweet black tea, although it can be made with green tea too. It contains a cocktail of diverse microbial life 18. Kombucha is also rich in fibre and protein – especially the amino acid lysine 9. Kombucha has been shown to help with a range of metabolic disorders and maintenance of general health 10.

Along with bacteria, kombucha tea is also a rich source of antioxidants 9 and the micronutrients zinc, copper, iron, manganese, nickel and cobalt 11. Vitamin B1, B6 and B12 and Vitamin C are also in this nutritious tea 11.

3.       Fibre

I wrote a whole blog on the other benefits of fibre** but one of the main benefits to eating fibrous foods is feeding your good bacteria. Although fibre isn’t a bacteria containing food, it does change the type of bacteria that can live in your intestines – it is a ‘prebiotic’ 12.

In one study, eating fibre changed the microbial fingerprint of individuals to the type seen in healthy, lean individuals rather than that typically seen in obese individuals 13. In other words, the fibre fed the kind of bacteria which are usually seen in lean people and starved those usually seen in over-weight people.

This is really significant because studies have shown that changing the bacteria in a mouse from the ‘lean’ microbial fingerprint to the ‘obese’ microbial fingerprint can cause mice to lose or gain weight – without any change to their diet. It might be that for some people, the type of bacteria in their intestine is causing them to be overweight, rather than their diet 14.

4.       Miso

Miso is a type of Japanese seasoning made from fermented soybean, barley or brown rice. Miso soup is a classic example of how this seasoning is used – simply dissolve a tablespoon of the paste like substance to soup to add flavour and good bacteria. This should be done after cooking, to make sure the probiotic bacteria are not killed in the cooking process. Its soybean base also means miso is rich in protein.

5.       Tempeh

Tempeh is also made from fermented soybeans. The finished product is a solid substance often used as a meat substitute. The taste of raw tempeh is quite strong, meaning it is often cooked to reduce the strong flavour. Fermented soybean products such as miso and tempeh have been shown to contain Lactobacilli and improve intestinal health, while also preventing the growth of bad bacteria in the intestine 15.

6.       Kefir

Kefir is a drink made by adding kefir grains to milk (or coconut water for dairy free kefir) and allowing the mixture to ferment. During the fermentation process the bacteria in kefir get rid of the lactose in milk, meaning people who are lactose intolerant may be able to drink kefir with no ill effects 16.

Kefir contains many different types of bacteria, some of which are known to produce molecules that fight ‘bad’ bacteria in your intestine 16. Regularly drinking kefir may also lower your chances of some cancers, although this may be because of other lifestyle factors associated with drinking kefir 16. Kefir may also be anti-inflammatory, which could be why it lowers the risk of cancer 16. It also improves digestion, lowers cholesterol and lowers blood pressure 16.

7.       Yoghurt

Probably the most well know probiotic containing foods are fermented dairy products such as yoghurts. There are now other yoghurts based on coconut rather than dairy which contain probiotic bacteria – great news if you can’t eat dairy. Yoghurts generally contain Lactobacilli and Bifidobacterium – two of the most well know ‘good’ bacteria. Eating probiotic containing dairy products has been shown to decrease chances of getting inflammatory bowel disease 6. They also help prevent infection with bad bacteria 17.


There are lots of foods that contain bacteria. Usually they’re preserved by fermentation – a natural process involving bacteria. Eating foods containing bacteria may improve the composition of your microbiome leading to multiple health benefits. Do you enjoy eating any foods that contain bacteria? Have you found they improve your health? Let us know in the comments below!


Vicky has a degree in Biological Sciences with a focus on biochemistry and immunology and is currently studying for a  MSc in Drug Discovery and Protein Biotechnology.  She is also an endurance athlete.


About Lucy Bee

Any information provided by us is not intended to diagnose, treat, cure or prevent disease. We always recommend referring your health queries to a qualified medical practitioner.

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