Lactobacillus vs Bifidobacterium: What's the Difference and Do You Need Both?

Lactobacillus and Bifidobacterium are the two groups of bacteria you will see most often on probiotic labels, and the main difference in your food is where you find them. Lactobacilli occur naturally in many fermented foods, such as yoghurt, kimchi and sauerkraut, while bifidobacteria rarely do. They mostly reach your plate because they have been added to yoghurts and fermented milks by producers. Inside your body they work in different parts of the gut and do different jobs, and most adults carry both.

What is the difference between Lactobacillus and Bifidobacterium?

Lactobacillus and Bifidobacterium differ in where you find them in food, what they feed on and where they work in your gut. Lactobacilli do not need oxygen to grow, but most can survive in it, so they are easy to keep alive in food. They are also already present on vegetables and tolerate the acid they make, which is why they thrive in ferments like kimchi and sauerkraut. Most bifidobacteria survive poorly when exposed to oxygen, which makes them harder to keep alive in food.

What are the benefits of Lactobacillus and Bifidobacterium in your diet?

Eating foods with live Lactobacillus and Bifidobacterium is linked to a more diverse gut microbiome and easier lactose digestion, and specific strains of each have been studied for digestive and vaginal health.

1. A more diverse gut microbiome. In a Stanford trial, 18 healthy adults who gradually increased the fermented food in their diet over 10 weeks, including yoghurt, kefir, kimchi and kombucha, ended up with more diverse gut bacteria and lower levels of inflammatory markers in their blood. Most of the new bacteria did not come from the foods themselves, which suggests fermented foods change the gut environment as well as adding microbes.
2. Easier lactose digestion. The live cultures in yoghurt break down some of its lactose, which is why many people who are lactose intolerant can eat yoghurt more comfortably than milk.
3. Fibre turned into fuel for your colon. Bifidobacteria break down fibre into acetate and lactate, which other gut bacteria then use to make butyrate, the main fuel for the cells lining your colon.
4. Vaginal health. Lactobacilli are the main bacteria in most healthy vaginas, where the lactic acid they make keeps the environment acidic. Specific strains have been studied for vaginal health.

Most of this evidence comes from fermented foods as a whole or from specific strains in supplements. A food's strains and live counts are rarely listed, so it cannot promise the effects found for a particular strain.

What happens to the bacteria you eat?

Some survive the journey, but most do not stay. Food bacteria face stomach acid, bile and competition from the bacteria already living in your gut, and most pass through and are no longer detectable soon after you stop eating them. Four things decide how many make it through:

1. The strain. Some strains tolerate acid and bile far better than others, even within the same species.
2. How the food was made and stored. Heating after fermentation kills the cultures. Live counts in yoghurt also fall the longer it sits in the fridge, and bifidobacteria, which are more sensitive to oxygen and acid, tend to decline faster than lactobacilli.
3. What you eat it with. Food buffers stomach acid, so bacteria eaten with a meal tend to survive better than on an empty stomach.
4. Your own gut. The bacteria already in your gut affect whether newcomers can find a foothold, which is why the same strain settles in some people and not in others.

Despite this, bacteria still do useful work while passing through. They break down lactose, make useful acids, and interact with your gut lining on the way. That is why a regular serving matters more than a large one. The same applies to probiotic supplements, where effects linked to most strains fade after you stop taking them. If you are pregnant or have a weakened immune system, check with your doctor before eating unpasteurised ferments.

Is it better to have both in your diet?

Having both makes sense because they work in different parts of your gut and do different jobs, so they complement each other. Lactobacilli work mainly in the small intestine, making lactic acid from simple sugars. Bifidobacteria work mainly in the colon, breaking down fibre and passing acetate and lactate on to the bacteria that make butyrate. Think of them as two specialists working in different rooms of the same house.

Even though there are currently no studies examining whether eating or taking the two together works better than either alone, a varied diet that includes fermented foods and plenty of fibre has been shown to confer health benefits.

How do you feed the Bifidobacterium you already have?

Eat more fibre, especially prebiotic fibres (fibres that gut microbes use selectively, with a health benefit), because bifidobacteria rely on the fibre that reaches your colon undigested. Good everyday sources include:

• Onions, garlic, leeks and spring onions
• Slightly green bananas
• Oats, barley and other whole grains
• Beans, lentils and chickpeas
• Asparagus and chicory root

Bifidobacterium levels tend to fall with age, so fibre becomes more relevant over time. In a study of Japanese people ranging from newborns to 104-year-olds, the share of Bifidobacterium fell after weaning and fell again in older age.

If you would like to know your own starting point, a gut microbiome test can show your Bifidobacterium levels and compare them with a reference database built on Asian gut microbiomes, so your results are set against people whose diets and backgrounds are closer to yours. Lactobacilli are usually too scarce in stool to measure reliably, which is why Bifidobacterium is the more useful marker here.

What does the research say about probiotic supplements?

Research on probiotic supplements is still emerging, and it is becoming more precise as newer trials test named strains, at set doses, for specific outcomes. So far, it supports specific strains for a few specific situations, while the evidence for most other uses is limited or mixed for now. Most trials have been done in people with a particular problem, so evidence for healthy people taking probiotics for general wellbeing is thinner.

The clearest evidence is for antibiotic-associated diarrhoea. A Cochrane review of 23 trials in nearly 3,900 children found that 8% of those given probiotics alongside antibiotics developed diarrhoea, compared with 19% of those who were not. The best results came from Lacticaseibacillus rhamnosus (formerly Lactobacillus rhamnosus) and the probiotic yeast Saccharomyces boulardii.

Why AMILI's formulas use both

Each of AMILI's four probiotic formulas pairs Lactiplantibacillus plantarum and other lactobacilli with one or more of Bifidobacterium breve, B. longum and B. lactis (B. animalis subsp. lactis), so the strains in each formula are designed to complement each other along the gut.

Each formula also contains prebiotic fibres: fructo-oligosaccharides (FOS), guar gum and orange peel extract. These were chosen because, in AMILI's lab research, they promoted the growth of Bifidobacterium. Here is how each formula is put together.

This article is for general information and isn't a substitute for personalised medical advice. If you have ongoing gut symptoms, speak with a doctor.

Glossary

• Acetate: A short-chain fatty acid and the main product bifidobacteria make from fibre. Other gut bacteria use it to make butyrate.
• Butyrate: A short-chain fatty acid made by certain colon bacteria. It is the main fuel for the cells lining the colon.
• Colony-forming units (CFU): A measure of how many live microbes a product contains. Probiotic doses are usually given in billions of CFU.
• Fermented food: A food made through desired microbial growth and the conversion of food components by microbial enzymes.
• Human milk oligosaccharides (HMOs): Complex sugars in breast milk that babies cannot digest but bifidobacteria can.
• Lactic acid bacteria: In the strict sense, bacteria in the order
• Lactobacillales, which mainly produce lactic acid. Bifidobacteria are often grouped with them but are not part of this order.
• Prebiotic: A food component, usually a fibre, that is selectively used by microbes in the body and provides a health benefit.
• Probiotic: Live microorganisms that provide a health benefit when taken in adequate amounts.
• Starter culture: Microbes added by producers to begin fermentation, such as the bacteria used to make yoghurt.
• Strain: A genetically distinct type within a species, usually shown as a code after the species name. Findings for one strain do not automatically apply to another.