Good and bad bacteria

Good and bad bacteria

Bacteria live throughout our whole body, with the average healthy adult having 100 trillion good and bad bacteria in the gut alone! These microscopic bacteria outnumber our human cells 10 to 1. Based on these numbers – we humans are 95% bacteria!  The balance of our good and bad bacteria is constantly changing, responding to our environment and our diet.

The food we eat, is more than just calories, vitamins and minerals. Our meals provide prebiotics or ‘food’ to our gut bacteria, regulating our good and bad bacteria mix. In turn these bacteria show their appreciation by keeping our bodies in balance. Long term dietary patterns can have an impact on our good and bad bacteria in our gut. Do you give these 100 trillion good and bad bacteria the attention they deserve?

There are many known health benefits associated with the balance of good and bad bacteria in our gut.

Good and bad bacteria – Nutrition & Digestion

The good bacteria that live in our digestive tract support the body in optimal nutrition and digestion by synthesising vitamin K, certain B Vitamins and nutrients – such as Short Chain Fatty Acids (SCFA).

SCFA are produced following the fermentation of food by our gut bacteria, which in turn help the good gut bacteria to thrive. SCFA are a fuel for the cells lining our large bowel, aiding absorption of nutrients and water, keeping our bowels happy and healthy and helping to reduce diseases such as Bowel Cancer. 

good and bad bacteria

good and bad bacteria

Good and bad bacteria – Immune system

Any bad bacteria, that make it through the protective stomach acid, are met by these trillion good bacteria. The good and bad bacteria compete by producing natural antibiotics to kill off these invading germs. Not only that, but the good bacteria teach our immune system how to fight off bad bugs that make us ill and ignore the things that aren’t a threat, generating ‘friendly’ signals to our immune system.

Good and bad bacteria – Disease

When the balance between our good and bad gut bacteria gets out of kilter, it can be associated with a number of diseases and conditions – such as Irritable Bowel Syndrome (IBS), Inflammatory Bowel disease (IBD), Diabetes, Obesity, Heart disease, Allergic disorders, Coeliac disease, Asthma and certain Cancers.

The research around the role our good and bad bacteria play in our health is constantly evolving with exciting discoveries. What is clear is that these trillions of microbes play an astoundingly important role in our health and need to be looked after.

Looking after your bacteria

Good and bad bacteria

Good and bad bacteria

Our good and bad bacteria are constantly changing in response to our environment and our diet. Exciting research is emerging around the role of yoghurt and probiotic (good bacteria) supplements in the balance between our good and bad bacteria. Research is also increasingly helping us to understand the role our diet plays in influencing the balance of good and bad bacteria. Many foods act as a prebiotic (food for your good bacteria), so the usual healthy eating advice applies – a varied diet high in fruit, vegetables and wholegrains to supply food to our bacterial friends.

Are you worried about food intolerances? Or have you cut certain foods out of your diet? Discuss any foods that you’ve eliminated from your diet with a Dietitian and look after your good and bad bacteria balance.

If you liked the blog – ‘Good and bad bacteria’, you might also want the read ‘Health benefits of yoghurt’.

photos by: NIAID & muammerokumus
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Registered Dietitian and owner of The Internet Passionate about family nutrition and the dietary treatment of Irritable Bowel Syndrome (IBS) Busy mum of 3 little uns. Cheshire, UK

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Leave A Reply (4 comments so far)

  1. Philip Taylor
    4 years ago

    Finally someone tells the truth about our gut flora. Everyone talks about the “good” bacteria and taking “good bacteria” probiotics. You are absolutely right the balance of the gut flora is a distribution of many type of bacteria, yeasts, and fungi. There too many strains so adding just a constant source of limited good bacteria strains not only affects the balance, but the distribution of the biodiversity of the gut environment. There are detriments and benefits to both worlds – the good, the bad, and the ugly (which no one even mentions). If we do not even completely understand the complexity of all of our human cells than how can we possibly understand the more complex world in our guts. Seems to me we have only scratched the surface to the possible and all the interactions in the community of our gut flora. I strongly feel that eliminating or altering the distribution in our gut can have dramatic and unforeseen implications. We cannot have a myopic view of a world that is diverse and complex. Taking probiotics has shown benefits but to what avail. To my knowledge there is no long term efficacy as taking them seems to be a fad.

    • Sian Riley
      4 years ago

      Hi Philip,
      Thanks for your thoughts and your feedback on the blog 🙂
      You’re so right, gut bacteria and it’s role in our health is such a complex world.
      I do think there is a place for probiotics and ‘good bacteria’ from fermented foods such as yoghurt, but we need to not neglect our diet in the pursuit of getting the ‘balance right’.

  2. Marina Christou
    3 years ago

    I would like to investigate and make sure my gut is working properly.
    I frequently suffer from trapped gas.
    I believe I eat healthily exercise drink water etc
    I am not over weight, but have developed a pop belly in the last yr

  3. will
    2 years ago


    Good read and simply articulated, but a side note to this would be:

    I am half way through a clinical nutrition course and recently I approached my local Pharmacy and asked why amongst all the supplements, they don’t sell Probiotics, given that they are handing out antibiotics all day long.

    I was not given a coherent answer, but questioned as to my motive for asking, as their reply was like some scripted marketing promo explaining that short term use of antibiotics causes no long term damage.

    It is alarming that in my Pharmacy they can sell you sweets, soft drinks, and other rubbish, which contribute to dental visits, obesity and diabetes, but but they will not sell probiotics to replenish the Micobiome, Maybe they want you to have further G.I.Tract disorders as that would be good for business.


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