Bitesize digest
- Bifidobacterium is a key "good" bacterium that supports digestion, immunity, vitamin production, and overall gut balance.
- Levels are highest in infancy and fall to a small share of gut bacteria in adults, declining further with age.
- Low levels are linked to digestive problems, weaker immunity, and some chronic conditions, and have been associated with mood through the gut-brain axis.
- You may be able to support your Bifidobacterium levels by eating fermented foods with live cultures (like yoghurt, sauerkraut, kimchi), feeding them with prebiotic fibres (like garlic, onions, bananas, oats), or taking supplements that name their Bifidobacterium species.
Bifidobacterium is a family of beneficial bacteria that play a central role in keeping the gut healthy. It is one of the most researched bacteria in the human body and is found mainly in the colon.
This group of microbes is one of the first to colonise the human gut during infancy, particularly in breastfed babies. Often called a "good" bacterium, it helps with digestion, supports the immune system, and contributes to a balanced gut microbiome, which is associated with a lower risk of gut dysbiosis, an imbalance in the gut bacteria.
What is Bifidobacterium?
Bifidobacterium naturally inhabits the gastrointestinal tract, vagina, and mouth. These bacteria are among the most studied of the live cultures found in the human gut, and their species appear in many supplements designed to support gut health. The name comes from the forked, Y-shaped cells many species grow in: 'bifid' means split in two.
There are many species of Bifidobacterium, including:
- Bifidobacterium longum
- Bifidobacterium bifidum
- Bifidobacterium breve
- Bifidobacterium infantis
- Bifidobacterium animalis
The benefits of Bifidobacterium
- Supports digestion: Bifidobacterium helps digestion by fermenting the complex carbohydrates and dietary fibres the body cannot break down on its own.
- Produces short-chain fatty acids (SCFAs): Bifidobacterium makes acetate, which other gut bacteria feed on and convert to butyrate. SCFAs are compounds your gut bacteria produce when they break down fibre, and butyrate in particular is a main energy source for the cells lining the colon and helps support the gut barrier.
- Protects the gut from harmful bacteria: it can inhibit harmful bacteria, including Clostridium difficile and Escherichia coli, by producing lactic and acetic acid, lowering gut pH, and competing for nutrients and space.
- Supports the immune system: Bifidobacterium helps regulate immune responses, and its fibre-derived SCFAs have anti-inflammatory properties.
- Synthesises vitamins: some species help produce B vitamins.
These roles are set out in a review of bifidobacteria and the butyrate-producing bacteria they feed (Riviere et al., 2016, Frontiers in Microbiology), and in a wider review of how Bifidobacterium uses dietary and milk carbohydrates across life (Xiao et al., 2024, npj Biofilms and Microbiomes).
What is a healthy level of Bifidobacterium?
There is no single agreed "healthy" number, and levels change a lot across life. In breastfed, vaginally born infants, Bifidobacterium can make up most of the gut bacteria; in adults it settles to a much smaller share, often under 5%, and it tends to fall further in older age (Riviere et al., 2016; Arboleya et al., 2016, Frontiers in Microbiology). These figures are averages across studies, and healthy people sit across a wide range.
The infant species are specialists: Bifidobacterium breve, Bifidobacterium infantis and Bifidobacterium longum dominate early on because they are well suited to feeding on the sugars in breast milk (Xiao et al., 2024). In children, low levels of Bifidobacterium in the gut have been linked to eczema. Much of the Bifidobacterium a baby carries is passed on from the mother: a 2025 review of 810 mother-infant pairs estimated that around 30% of species are shared, more often after a vaginal birth (Flores Ventura et al., 2025, npj Biofilms and Microbiomes).
What happens if Bifidobacterium levels are too low?
Low levels of Bifidobacterium have been linked to a range of health problems. These are associations researchers report, not proof that low levels cause the condition.
Digestive issues
- Greater susceptibility to bloating, gas, diarrhoea, Indigestion or constipation.
- Reduced breakdown of dietary fibre. Fibre is central to producing short-chain fatty acids, so with fewer Bifidobacterium to break it down, fewer SCFAs are produced.
Weakened immune system
- A greater risk of infections and ongoing inflammation, as Bifidobacterium helps regulate immune responses and produces SCFAs, which are associated with lower levels of inflammation.
Gut dysbiosis
- An imbalance in gut bacteria can allow harmful microbes to overgrow. Gut dysbiosis has itself been linked to several chronic conditions.
Chronic conditions
- Low levels of Bifidobacterium are linked to several chronic diseases such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and metabolic conditions like obesity and type 2 diabetes. A systematic review of 24 studies found people with IBS tend to have lower Bifidobacterium than people without it, though whether that is a cause or a consequence of IBS is not yet known (Pittayanon et al., 2019, Gastroenterology).
Mental health
- Bifidobacterium contributes to the gut-brain axis, the two-way communication pathway between the gut and the brain. Some small studies have found lower levels in people with depression, but this research is limited and shows an association only, not that low levels cause low mood.
Autoimmune conditions
- Low levels have been associated with a higher rate of allergies and autoimmune conditions, such as eczema and rheumatoid arthritis.
How to increase Bifidobacterium levels naturally
There are two broad routes: feed the Bifidobacterium already living in your colon, or take in live bacteria through fermented foods and supplements. The first has the stronger evidence, which is why it comes first here.
Focus on prebiotic foods
Prebiotics are fibres your body cannot digest but your gut bacteria can. They are the best-evidenced way to raise Bifidobacterium through food: a meta-analysis of 64 trials in around 2,000 adults found that fibre supplements increased Bifidobacterium, with fructans (inulin-type fibres) and galacto-oligosaccharides having the clearest effect (So et al., 2018, American Journal of Clinical Nutrition). Overall diversity did not change in those trials, which points to fibre feeding the bacteria you already have rather than adding new species. Key sources include:
- Chicory root
- Jerusalem artichokes
- Garlic
- Onions
- Asparagus
- Bananas
- Whole grains, like oats and barley
- Legumes and pulses
- Polyphenol-rich foods like berries, apples, tea, herbs, dark chocolate, and flaxseeds.
Our guide gives a full breakdown of the best foods to eat for gut health.
Eat fermented foods with live cultures
Fermented foods with live cultures, such as live yoghurt, sauerkraut, kimchi, miso and tempeh, contain beneficial bacteria and may help support gut health. In one 17-week trial, a diet rich in fermented foods increased the overall variety of gut bacteria and lowered markers of inflammation, though the study was small and did not single out Bifidobacterium (Wastyk et al., 2021, Cell). For live yoghurt, look for active cultures that list Bifidobacterium species; for sauerkraut and kimchi, choose chilled, unpasteurised versions, as shelf-stable jars are usually pasteurised, which kills the live cultures.
Consider supplements with live cultures
Many supplements with live cultures contain strains of Bifidobacterium. Look for products that name their strains, such as B. longum, B. bifidum, or B. breve. The evidence here is less consistent than for fibre, and results from one named species do not automatically carry over to another, so a vague 'live cultures' label on its own tells you little.
Breastfeeding for infants
Breast milk is a natural source of oligosaccharides, which encourage the growth of Bifidobacterium in infants. Some formula milks include added live cultures, such as Bifidobacterium species. This is background on why Bifidobacterium features so strongly in infant guts, not feeding advice: how to feed a baby is a decision for parents to make with their midwife or health visitor.
Why diversity and balance are key
The key to a healthy gut is diversity and balance, with each species contributing something different. Bifidobacterium is important, but its dominance should not overshadow other beneficial microbes such as Lactobacillus and Akkermansia. A diverse microbiome supports digestion, helps keep immune responses balanced, supports the gut-brain axis, and creates the competition that limits harmful overgrowths. That is one reason the advice above leans on a variety of plant foods rather than a single fibre: a varied diet feeds a range of bacteria, not just Bifidobacterium.
What can decrease Bifidobacterium levels?
Several things can disrupt gut balance and lower the levels of Bifidobacterium and other beneficial bacteria, including:
- Poor diet or a Western diet: diets high in processed foods, sugar, alcohol, and additives, and low in fibre, can harm beneficial bacteria.
- Stress: chronic stress disrupts the gut-brain axis and affects microbial health.
- Certain medications: broad-spectrum antibiotics kill both good and bad bacteria, which disrupts the balance of the gut microbiome. Longer-term use of medicines like NSAIDs such as naproxen and Proton Pump Inhibitors including Omeprazole may also reduce Bifidobacterium levels; one study of 1,815 people found PPIs were associated with a shift towards a less healthy gut microbiome (Imhann et al., 2016, Gut). None of this is a reason to stop or change a prescribed medicine: if you are worried about a medicine you take, speak to your GP or pharmacist.
- Ageing: Bifidobacterium levels naturally decline with age, which is part of why diet matters more over time.
- Gut parasites: certain intestinal parasites such as Cryptosporidium and Giardia Lamblia can compete with beneficial bacteria for nutrients and space, sometimes reducing their numbers. Because some parasites can sit in the gut for years without obvious symptoms, an at-home gut parasite stool test can help detect them early.
Why should I test my Bifidobacterium levels?
When your gut is balanced, you are less likely to experience common digestive issues or irregular bowel movements.
Gut microbiome testing of this kind is not part of routine NHS care, so seeing your levels means using a private test. A gut bacteria test can assess the levels of Bifidobacterium in your gut, along with other beneficial and harmful bacteria that affect the overall balance. It also comes with nutritional and supplement suggestions to help address any imbalances it identifies.
It is worth being clear about the limits, too. A test is a snapshot of a single sample, and for most gut bacteria the day-to-day variation within one person can be larger than the differences between people, so one reading is a guide rather than a fixed value (Vandeputte et al., 2021, Nature Communications). There is no single agreed "healthy" level of Bifidobacterium, and a test does not diagnose any condition.
When to see a GP
Gut symptoms are usually not about your Bifidobacterium levels, and some need proper medical checks rather than a test. See your GP if you have any of the following:
- Blood in your stool
- Unexplained weight loss
- A change in your usual bowel habit lasting more than three weeks
- Difficulty swallowing or persistent vomiting
- Iron-deficiency anaemia
- New bowel symptoms if you are over 50, or a family history of bowel or ovarian cancer
These can have many causes, most of them treatable, but they should be looked at by a doctor rather than managed at home. If you are not sure whether a symptom needs an appointment, NHS 111 can help you decide.
Sources
- Riviere et al., 2016, Frontiers in Microbiology: review of bifidobacteria and the butyrate-producing gut bacteria they feed.
- Xiao et al., 2024, npj Biofilms and Microbiomes: review of how Bifidobacterium uses dietary and breast-milk carbohydrates across life.
- Arboleya et al., 2016, Frontiers in Microbiology: review of gut Bifidobacterium populations through life and in older age.
- Flores Ventura et al., 2025, npj Biofilms and Microbiomes: systematic review and meta-analysis of 810 mother-infant pairs.
- Pittayanon et al., 2019, Gastroenterology: systematic review of 24 studies of gut bacteria in IBS.
- So et al., 2018, American Journal of Clinical Nutrition: meta-analysis of 64 fibre trials in around 2,000 adults.
- Wastyk et al., 2021, Cell: 17-week trial of fermented-food and high-fibre diets.
- Imhann et al., 2016, Gut: proton pump inhibitors and the gut microbiome in 1,815 people.
- Vandeputte et al., 2021, Nature Communications: daily sampling study of within-person gut microbiome variation.
