Why do you need Bifidobacterium adolescentis?

Bifidobacterium adolescentis: Benefits of the Gut Bacterium That Feeds Other Gut Bacteria

Bifidobacterium adolescentis benefits your gut mostly by feeding other gut bacteria, and it is one of the main bifidobacteria that stay in the gut into adulthood. It breaks down fibre and starch from plant foods and releases acetate, which other gut bacteria use to make butyrate, the preferred fuel for the cells lining your colon. If you have seen B. adolescentis on a probiotic label, it helps to know what it does and how to feed it.

In short:

• B. adolescentis is one of the main bifidobacteria in adult guts, adapted to plant fibre and starch.
• Its main benefit is indirect: it turns fibre into acetate, which other bacteria use to make butyrate, a type of short-chain fatty acid that serves as the preferred fuel for the cells lining your colon.
• Onions, garlic, leeks, oats, and rice or potatoes that have been cooked and cooled supply the fibres and starches it uses.
• Human trials of specific strains are few and small, so most of what it does is known from laboratory studies.

What is Bifidobacterium adolescentis?

Bifidobacterium adolescentis is a bacterium that lives in the large intestine of adults and feeds on plant fibres and starches your own body cannot digest. In a Japanese study of 441 people aged 0 to 104, the guts of adults were dominated by B. adolescentis and its close relative B. catenulatum, while babies' guts were dominated by B. breve and B. longum.

That shift follows the diet. The bifidobacteria that dominate in babies are suited to the sugars in breast milk. B. adolescentis is suited to the solid, plant-based food that replaces it, which is why it stays with you into adulthood.

What does B. adolescentis do in your gut?

B. adolescentis breaks down fibres and starches into acetate and lactate, and other gut bacteria use those products to make butyrate. This handover between species is called cross-feeding, and it works like a relay. B. adolescentis runs the first leg, and butyrate producers such as Faecalibacterium prausnitzii finish the race.

F. prausnitzii is one of the most abundant bacteria in a healthy colon, and butyrate is the preferred fuel for the cells lining it. In a laboratory study, F. prausnitzii grown together with B. adolescentis on fibre made more butyrate than F. prausnitzii grown alone, and the acetate levels fell over the same period as F. prausnitzii used it up.

The benefits of B. adolescentis depend on the community around it. This is because your gut microbiome is an ecosystem, where what one species does depends on and impacts the others it lives with. At the moment, most research still tests one strain or species at a time, because single strains are easier to isolate, dose and measure. So the evidence on what B. adolescentis can do alone is still thin, and it may not capture everything it does in your gut, where its effects depend on which other bacteria are there.

What are the benefits of Bifidobacterium adolescentis?

The best-supported benefit of B. adolescentis is helping other bacteria make butyrate, shown in laboratory studies. Human evidence is limited to a few small studies of specific strains.

• More butyrate from fibre. In laboratory co-cultures, B. adolescentis raised the butyrate that F. prausnitzii made from fibre and starch.
• A response to resistant starch. In a study of 10 adults who ate crackers made with different types of resistant starch for three weeks each, one type (chemically modified wheat starch) raised B. adolescentis, and bifidobacteria rose about tenfold in three of the participants.
• Fewer symptoms of lactose intolerance. In a two-week pilot trial of 21 people with lactose intolerance, the strain iVS-1 at 1 billion CFU a day reduced symptoms such as bloating, abdominal pain and diarrhoea compared with placebo. Researchers linked to the company that sells the strain were among its authors.
• GABA production. Some B. adolescentis strains produce GABA, a compound that carries signals in the nervous system, and two strains raised GABA levels in rats. This has not been tested in people.
  

How do you increase Bifidobacterium adolescentis naturally?

You can feed the B. adolescentis you already have with inulin-type fibres and resistant starch, the two kinds of carbohydrate it is equipped to break down. Foods that supply them include:

• Inulin-type fibres: onions, garlic, leeks, chicory and slightly green bananas.
• Resistant starch: oats, barley, legumes, and rice or potatoes that have been cooked and then cooled, since cooling turns some of the starch into a resistant form.

Responses vary between people, because a fibre can only feed the bacteria that are already there. If you do not eat much fibre now, adding a lot at once can cause gas and bloating for a week or two, so increase it gradually. Begin with one small step: swap one serving of freshly cooked rice this week for rice that was cooked and cooled in the fridge.

Is Bifidobacterium adolescentis safe?

For most healthy adults, yes. B. adolescentis is a normal resident of the adult gut, and bifidobacteria have a long history of use in food and supplements. Side effects reported in trials of bifidobacteria are usually mild and digestive, such as gas or bloating in the first days.

Speak to a doctor before starting any supplement if you are immunocompromised, pregnant or breastfeeding, taking prescribed medication, or managing a diagnosed condition.

Does taking Bifidobacterium adolescentis as a supplement work?

A B. adolescentis supplement can only help if a live strain survives the capsule and your stomach and then becomes active in your colon, and the research on each of those steps is still early. Having it in your gut and getting it there from a capsule are separate questions.

Survival is the first hurdle. Bifidobacteria differ in how well they survive oxygen and stomach acid, so how a product is made, packed and delivered matters.

Once it arrives, its advantage is that it is adapted to the adult gut. In a three-week trial in adults with obesity, the strain IVS-1 reached higher numbers in stool than BB-12, a common commercial strain that is not native to the human gut, and raised total bifidobacteria about as much as the prebiotic GOS did. Taking IVS-1 was also linked to better results on one test of gut barrier function.

In most probiotic trials, supplemented strains are found mainly while people are taking them, which is why probiotics are usually taken every day. A strain does not need to settle permanently to be active. While it passes through your colon, it can break down fibre and pass acetate to the butyrate producers already living there, the cross-feeding described above. Regular doses keep it present for that, although this handover has so far been shown mainly in laboratory studies.

Glossary

• Acetate: A short-chain fatty acid that 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 preferred fuel for the cells lining the colon.
• CFU (colony-forming units): A measure of how many live microbes a product contains.
• Cross-feeding: When one gut bacterium's products become another bacterium's food, as when B. adolescentis produces acetate that butyrate producers use.
• GABA (gamma-aminobutyric acid): A compound that carries signals in the nervous system. Some gut bacteria can produce it.
• Inulin: A type of fibre found in onions, garlic, leeks and chicory, which bifidobacteria can break down.
• Lactose intolerance: Difficulty digesting lactose, the sugar in milk, which can cause bloating, pain and diarrhoea.
• Resistant starch: Starch that escapes digestion in the small intestine and is broken down by bacteria in the colon.
• 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.