Friendly gut bacteria explained

Expertly reviewed by Dr Ro Huntriss, Consultant Dietitian and Nutritionist

Did you know that there are trillions of microorganisms living inside your gut?

They’re collectively known as your microbiome and each person’s is unique – a bit like your genes. The microbiome is formed from the moment you’re born, but microbes in your gut help to shape it as you go through life.

The potential effects your microbiome can have on your wellbeing shouldn’t be underestimated, which is why it’s so important to have a healthy gut.

For example, your gut may affect your weight. Studies on twins have shown that family members have similar gut microbes, which indicates that your microbiome could affect how much body weight you gain and where you store it.

So what’s all the fuss about?

Now, unless you’ve been living on a tropical island for the past few years (which does sound lovely, by the way), you’ll have heard the hype surrounding friendly bacteria and the benefits they have on our gut health.

Scientists are still discovering exactly how our gut impacts our wider health and wellbeing, but we do know that friendly, or ‘good’, bacteria play a key role. With the expert advice of Dr Ro Huntriss, Consultant Dietitian and Nutritionist, we’ve got your friendly gut bacteria explained.

In this article, you’ll discover

• What bacteria is
• What friendly bacteria is and what it does
• Types of friendly bacteria
• How diet affects the microbiome

What are bacteria?

Bacteria are tiny living organisms – usually consisting of just one cell – that can be found just about anywhere, including our guts!

Many strains of bacteria are ‘good’ and help our body perform certain tasks. However, some are harmful and can cause infections and illness.

The key is to strike a balance between good guys and the bad.

Researchers say that when our microbiome is out of balance (known as dysbiosis), it can cause health issues which may lead to an increased risk of conditions like heart disease.²

What is friendly bacteria?

Next time you pick up a live yoghurt that’s packed with friendly bacteria, take a look at the label.

It may contain Lactobacillus acidophilus or Bifidobacterium bifidum – these are common bacterial cultures that have been shown to have a beneficial effect on certain aspects of our health.³

They’re called ‘good’ or ‘friendly’ bacteria because they can help restore the balance in our gut following a bout of diarrhoea, a course of antibiotics or an episode of irritable bowel syndrome (IBS), for example.⁴

Why bacteria matters

It’s not just about digestion, though. Scientists are now beginning to discover that beneficial gut microbes can positively impact other aspects of our health.

For example, certain types of fibre are fermented in your large intestine by gut bacteria, producing short-chain fatty acids. These have been shown to support your immune system and general wellbeing.⁵

Resistant starch, another type of fibre which can be found in oats, legumes and some whole grains, has also been shown to feed good gut bacteria. Studies suggest it may be linked with managing the risk of obesity.⁶

What do friendly bacteria do?

Friendly bacteria have mainly been studied for their beneficial effect on gastro-intestinal issues such as traveller’s diarrhoea, antibiotic-associated diarrhoea, IBS and inflammatory bowel disease (IBD).⁷

But there are some new areas of research that show good bacteria may also be helpful for:

1. Dental health  – it’s thought that replacing bad bacteria in your mouth with good bacteria can help protect your teeth and gums.^8,9
2. Mood – a 2017 Canadian study found friendly bacteria could reduce anxiety and symptoms of depression, most likely due to the gut-brain axis; the link between our gut and central nervous system.¹⁰
3.  Urinary tract infections – taking friendly bacteria may help re-balance bacteria in the vagina and bladder, fighting infections¹¹ However, research into this area is in the early stages and there are no definite conclusions yet.
4. Eczema - Beneficial bacterial may ease symptoms.¹²
5. Immunity – Around 80% of your immune system is in your gut and friendly bacteria play a key role.¹³
6. Weight management – Good bacteria may help you to maintain a healthy weight, although evidence for this is limited and more research is required.

Research for all of the above is in the early stages and is ongoing, but it may be worth increasing your intake of friendly bacteria if any of the above conditions are a concern for you.

Types of friendly bacteria

These bacteria are some of the most beneficial in terms of keeping your digestion and gut healthy:

1. Lactobacillus

This strain plays a key role in gut health.

Found in the mouth, gastrointestinal tract and female genital tract, lactobacillus produces lactic acid and helps to protect against harmful microorganisms.¹⁴

A 2016 report published in World Journal of Gastroenterology found that lactobacilli can ease symptoms of IBS, like stomach bloating.^15,16

Handpicked content: What is Irritable Bowel Syndrome (IBS) and how can you treat it?

2. Bifidobacteria

This is the first strain to colonise babies’ guts, and it’s also thought to play an important role in immune system health.

There is some evidence to suggest that bifidobacteria may also ease the symptoms of IBS and could reduce the risk of babies developing eczema.^17,18

However, scientists are still investigating the mechanisms behind this.^19,20

Handpicked content: What is my immune system and why is it so important?

3. Christensenella

This type of friendly bacteria has been linked with a healthy gut as it helps to maintain microbial symbiosis – when different species of microorganisms inhabit the same space and benefit each other.^21,22

As part of a twin study at New York State’s Cornell University and King’s College London, researchers found that slim people have higher levels of a particular strain of this bacteria – Christensenellaceae minuta – suggesting it may play a role in managing body weight.²³

External influences

So we’ve seen that the gut microbiome influences many aspects of human health, from your immunity to your metabolism.²⁴

Both environmental exposure and your diet can affect the gut microbiome, find out more on the latter below.²⁵

How does your diet affect your microbiome?

What we eat has a big impact on the health of our gut and our individual microbiome can affect our metabolism, digestion and weight.

A large study in the Netherlands found that everything we drink or eat has an effect on the bacteria living in our digestive systems as well as our overall health.²⁵

Other evidence suggests that a diet high in sugar and fat changes the bacteria in the microbiome and increases the risk of obesity.²⁶

Researchers believe that a diverse diet leads to a diverse microbiome that is able to deal with harmful bacteria.²⁷

What is a microbiome diet?

The idea is to eat a diet full of foods that helps support levels of good bacteria in your gut.

A healthy gut diet plan is rich in whole foods and nutrients – basically, foods that help your digestive system work at its best - and less processed and harder-to-digest foods.

These can include:

• Fruit and vegetables

Packed with essential vitamins, minerals and dietary fibre, getting your 5 a day is essential for a healthy, balanced microbiome.

Aim to fill your plate with a variety of fresh fruit and veg like broccoli, spinach, carrots, blueberries, apples and strawberries.

• Herbs and spices

Flavour your food with aromatic spices like ginger and turmeric. Research suggests that adding herbs and spices to your food could positively affect the gut microbiota composition

How can I consume friendly bacteria?

Friendly bacteria are found in some fermented foods, such as kimchi, miso, sauerkraut and kombucha, a fermented tea.

These foods and drinks are more popular in other parts of the world, but they are starting to become widely available in the UK.

Most of us are currently more likely to consume good bacteria in yoghurts and yoghurt based drinks such as kefir, supplements or powders.²⁸

Friendly bacteria supporting foods

Foods that contain friendly bacteria may help restore good bacteria in your gut and keep it healthy.²⁹

In fact, the Netherlands study found that people who regularly ate yoghurt had more diverse gut bacteria.³⁰

• Omega-3s

Evidence suggests that Omega-3 fatty acids can help support the body’s natural immune response.³¹

To get your fill, go for oily fish like salmon or mackerel – the NHS recommends two portions a week. Chia seeds or flaxseeds are also good sources.

• Wholegrains

According to research, wholegrains aren’t just a nutritious way to provide your body with digestive-friendly fibre, they could also support the balance of bacteria in your microbiome by helping to feed them.³²

Staple wholegrains of a gut health diet include; porridge oats, brown rice, quinoa, bulgur wheat, barley, popcorn, whole-wheat bread and buckwheat.

These hearty grains may also keep you feeling fuller for longer.

• Red wine

In moderation, red wine could help keep your microbiome diverse.

It contains resveratrol, which one study found may lessen the risk of heart disease by adapting the gut microbiome.³³

What to look for in friendly bacteria

Not all good bacteria foods or supplements are made the same, so you need to know how to pick the right one for you:

• Does it contain enough friendly bacteria to be effective? In 2013, Italian researchers concluded that the amount for good general gut health was between 10 million to 1 billion CFU (colony forming units) a day.³⁴
• Will the bacteria reach your intestines intact? Many are destroyed by stomach acid before they can actually do any good in your gut.³⁵
• Are you taking the right one for your symptoms? Different types of bacteria may be better for certain conditions. It’s best to talk to your GP or a specialist dietician for advice if you’re unsure.³⁶

You can help support boost the good bacteria already living in your gut by eating fermented foods such as kimchi or sourdough bread, consuming more high-fibre foods to help feed your microbiome and tackling stress.

Stress can make your gut more sensitive (making IBS worse) and can lead to poor food choices that don’t feed your gut bacteria.³⁷

What is fibre?

Sometimes known as ‘roughage’, fibre is made up of a group of substances found in plant foods.

These include lignin, waxes and polysaccharides, such as pectin and cellulose. Most fibre passes through your digestive system, pushing food along and helping to keep bowel movements regular.

That’s why, if you don’t have enough, you can become constipated.

Handpicked content: What is digestion?

Are you getting enough?

Unfortunately, in the UK, we don’t eat anywhere near enough fibre to keep our tummy bugs happy.

We should have 30g of fibre a day but, on average, we only manage 18g – about 60% of what we should be aiming for. So our good bugs aren’t getting the fertiliser they need.⁴⁶

Go up gradually

Convinced you need more fibre? A word of warning before you start loading up on lentils, brown rice and veg.

Lots of people find they get more wind when they suddenly increase their intake, which is why it’s a good idea to increase it gradually.

This will settle as your gut gets used to your new way of eating.

And check with your doctor or nutritionist if you have IBS.

Guidelines from NICE (National Institute for Health and Care Excellence) state that, for people with IBS, it may actually be helpful to reduce high-fibre cereal-based foods such as brown bread and brown rice, as they are too much for a sensitive digestive system.⁴⁷

But you could discuss other ways to pack it into your diet.

Handpicked content: What is IBS and how can you treat it?

What foods should you avoid on a microbiome diet?

There are a few foods that you should avoid on a microbiome diet...

1. Alcohol

Research shows that drinking excessively or for long periods may affect the microbiome which could, in turn, lead to liver disease.³⁸

2. Refined carbohydrates

Evidence shows that eating refined carbohydrates on a regular basis could have an inflammatory effect on the body.³⁹

Instead, cut down on white bread and pasta in favour of whole grains, which are much better for a good gut health diet.

3. Hydrogenated fat

Research suggests that processed food that contains hydrogenated (trans) fat may cause inflammation.⁴⁰

These foods are also often high in calories, which may decrease the diversity of our gut bacteria.⁴¹

Making some changes to your diet helps support your microbiome, but remember that there is no “one size fits all” approach. 

“But there is a good correlation between diversity and health: greater diversity is better,” researcher Alexandra Zhernakova MD PhD says.

And Dr Kelleman agrees: “The key is to keep supporting your little friends inside — your microbiome.”

The final say

Thankfully, you can increase the level of friendly bacteria in your gut by eating a healthy balanced diet full of wholegrains, fruits, vegetables and fermented foods.

Or if you need a little extra help, try live friendly bacteria supplements that state on the packet that they’re priven to survive stomach acid. It’s usually best to take a multi-strain variety, rather than just one type of bacteria because diversity is key, but do check with your GP first.

The advice in this article is for information only and should not replace medical care. Please check with your GP or healthcare professional before trying any supplements, treatments or remedies. Food supplements must not be used as a substitute for a varied and balanced diet and a healthy lifestyle.

Last updated: 3 August 2022