Good Bugs, Bad Bugs, Your Diet and Probiotics

By Amanda Whitford

The word bacteria often comes with negative connotations of uncleanliness and illness, but in fact there are both good and bad bacteria that are vital for our health and well being.

The human gut is home to trillions of bacteria that begin colonisation at birth and continue to evolve throughout a person’s life span. There are hundreds of different types of bacteria and no two people will have exactly the same composition, however, it is the balance between numbers of good bacteria versus bad bacteria that seems to be the key to a healthy outcome

Gut bacteria have many important roles in our bodies.  At the most basic level they help digest our food and we have around 2 kilos of these bacteria in our gut.  They are able to break down certain food components that we are unable to, thus releasing more energy from our food

They can synthesise Vitamin K and some B vitamins, and produce short chain fatty acids that are the main food source for intestinal cells.

They have a role in shaping the immune system from birth, with inadequate numbers and/or composition being associated with food allergies and inflammatory gut diseases. They help to keep harmful microorganisms out of our body by blocking access to our inner gut surfaces, and by outcompeting them for food and space.

It’s not surprising then that if the balance of good to bad bacteria is upset and not reinstated, that our health can suffer. Along with disrupting the above functions, too many bad bacteria leads to increased exposure to their endotoxins, which cause an immune response and inflammation in the body. Low grade chronic inflammation is a major risk factor for many disease including irritable bowel disease, diabetes, obesity and cardiovascular disease and many studies have found links between these diseases and gut bacteria composition.


So what dictates the types of bacteria that reside in the gut?

Many factors affect this balance, but one of the biggest contributors is diet. This makes sense as gut bacteria feed off the food that enters our gut, each type having specific ‘food’ preferences. This means that diet will determine which bacteria get fed and can therefore multiply and colonise the gut.

Eating a nutritious, balanced diet is the best way to ensure a healthy gut flora balance.   The good bacteria love fibre which is yet another good reason to include plenty of fibrous veggies in your daily diet.  Unhealthy dietary habits, in particular high fat and high sugar diets are associated with higher numbers of ‘bad’ bacteria and the related health outcomes. Gut bacteria balance can also be affected by antibiotic medications, and by gastrointestinal illnesses. Usually in these situations a probiotic would be recommended to counteract this.

Probiotics are live bacteria that can be ingested in foods such as probiotic yoghurts and other fermented dairy products, or in supplement forms like pills or powders. Most of these will contain different strains of Lactobacillius and Bifidobacterium which make up the majority of our ‘good’ bacteria. The aim of probiotics is to get beneficial bacteria into our gut so it can colonise there. When choosing to take probiotics it’s important to look for those that are compatible with the human gut, are resistant to digestion, and if they are to combat antibiotics, it may to check with your doctor which species of bacteria the particular antibiotics target as these are what you will need to replace. If you taking probiotic capsules aim to use those which have around 25 billion good bacterial per capsule.

Prebiotics can also be a valuable tool in achieving desirable bacteria balance. Prebiotics are a type of dietary fibre that our digestive enzymes cannot breakdown so they reach the colon where they feed our ‘good’ bacteria, stimulating their growth. Prebiotics can be found in onion, garlic, leeks, asparagus and bananas, and like the probiotics can also be found added to foods or in supplement form.

While probiotics and prebiotics can help to reset and maintain bacterial balance in our gut, diet is still the most important factor here. Gut bacteria composition is transient and hugely affected by long term food intake patterns. If you eat a high fat or sugar filled diet, the changes this induces is going to be counterproductive to the effect of any probiotics or prebiotics that you ingest.


So what is the take home message from this? 

Strive to eat a healthy, low sugar, high fibre, real food diet as much as possible.


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