Gut Bacteria Diet : how does your diet affect your gut bacteria?
What does your microbiome like to eat?
Is there a good gut bacteria diet?
Find out about eating a variety of high fibre (fiber) foods in your diet for a healthy, diverse mix of gut bacteria.
Gut Bacteria feed on Fibre (Fiber)
Our gut bacteria breakdown the fibre in our food to feed themselves.
They create chemicals & vitamins vital to our health, in the process of releasing nutrients for themselves.
Dietary fibre is the indigestible part of the foods we eat, that our body can’t break down on its own.
These non digestible fibres are known as prebiotics, food for the good bacteria in our gut.
Which carbohydrates in our diet feed our gut bacteria?
Most of the foods we eat are made up of types of carbohydrates.
Only some types of carbohydrates are prebiotics (which encourage the growth of good gut bacteria):-
Simple carbohydrates or starches (like pasta, white bread, white rice) are broken down by our body’s own enzymes.
Shown on food labels as “sugars”, simple carbohydrates are short chains of different types of sugar molecules.
Our own enzymes can easily snip these into glucose (a type of sugar) without needing any help from the gut bacteria.
They are absorbed straight into the bloodstream from the small intestine, giving us an immediate burst of energy.
Gut bacteria eat the longer chains of carbohydrates which our body can’t digest with its own enzymes.
These pass undigested from the small intestine, to the colon, where gut bacteria break them down into new molecules.
Known as polysaccharides, dietary fibre, or complex carbohydrates, these are long chains of sugar molecules.
They are found in plant foods, and give structure to & store energy within the plant.
There are thousands of different types of polysaccharides in fruit & vegetables, beans and wholegrains.
For example, pectin, found in fruit, and inulin in onions.
Gut Bacteria also eat food sheltered within particles too large for our body to breakdown.
When we eat unrefined wholegrains like whole oats, the protective outer casing allows the oat inside to survive the journey to the colon mostly intact, where the bacteria can digest the coating & oat inside.
Quick cook / rolled oats have had the protective coating on the oat removed, meaning the carbs can be digested in the small intestine, broken into sugars & absorbed straight into the bloodstream.
Less processed foods aren’t as easily absorbed before reaching the colon, leaving plenty of food for our gut bacteria
Different bacteria eat different fibre
Different bacteria, living in different parts of the colon, feed on different types of prebiotic fibre.
Studies show that people eating diets higher in fibre have a larger variety of bacteria in their guts.
And importantly, lower rates of inflammatory diseases.
A more diverse microbiome (mix of bacteria) produces more helpful short chain fatty acids which calm our immune systems & boost our overall health.
Change your diet, change your gut bacteria : variety is key
The mix of bacteria in our gut is flexible and we can alter it by changing our diet
Our microbiome responds instantly to the food we choose to eat.
Gut bacteria can reproduce a new generation within half an hour when given suitable food.
Eat a banana, and the types of bacteria that feed on the type of fibre in bananas, will multiply fast, fueled by their favourite food.
Bacteria need the complex carbs found in fruit, vegetables, beans, and unrefined wholegrains.
By eating many different types of these high fibre foods that help friendly gut bacteria thrive, you can encourage a wide mix of helpful gut bacteria to thrive.
Consistency is key – we need to keep up the varied fibre intake to sustain gut bacteria in the long term.
Falling levels of Dietary Fibre
Modern changes to our diet & lifestyle mean the mix of bacteria in our guts has become less diverse:-
– Western diet of bland, pre-prepared, highly processed, industrially produced fast foods
– Antibiotics & use of antibacterial cleaners
Studies suggest than we now eat on average, less than 20 types of food a week, compared to estimates of 150+ for our ancestors
From the industrial revolution onwards, we have changed the food we eat:-
– Food is mass produced, processed & sanitised for longer shelf life.
– Artificially refined foods : biscuits, crisps, soft drinks, breakfast cereals
– Processed foods like ready meals, based on corn, soy, wheat or meat,
– Foods often bear little resemblance to their raw ingredients
Americans eat on average 10-15g fibre a day and the British, an average of 18g per day (NHS).
Compare this to the hunter gatherer tribes still existing in remote regions, scientists suggest they eat 100g-150g fibre daily.
Some estimates suggest our ancestors ate up to 150 types of ingredients a week and up to 100g of fibre each day.
Gut Bacteria Diet = A Varied High Fibre Diet : feed your microbiome for diversity
Plants are the key foods for our gut bacteria : eat as many types of fruit, veg, wholegrains, beans as you can.
– Eat the rainbow – lots of brightly coloured, nutrient dense fruit & vegetables
– Avoid processed snack foods, low fat / “light” foods & ready meals
– Choose nuts, fruit & seeds for snacks
– Consider eating foods in season, to increase the range of fruit & vegetables you consume, as well as seasonal fruit & veg being better value at the supermarket
– Chose wholegrain varieties of bread, oats, cereals
Gradually introduce more fibre to your diet gradually over a few weeks.
You may notice some extra wind (flatulence / gas) as the blend of bacteria in your gut adapts to their new food sources, which will soon settle down.
If you suffer from IBS or another gastric disorder, talk to your doctor before adding high fibre foods to your diet.
The Science Bit
The information I share on this site distills the research I’ve read on the microbiome, prebiotics & probiotics.
You’ll find links to the relevant research studies on each page.
I’m not a scientist / dietician / nutritionist. I’m a food lover & home cook, putting microbiome research findings into action in my kitchen.
Find out more about the scientists leading research into the microbiome on the FAQs page
Keep Reading : What Are Prebiotics?