Probiotics Cut Baby Infections: The 23% vs 40% Surprise

The missing ingredient wasn’t a medicine. It was sugar — not the candy kind, but complex sugars copied from breast milk, paired with the gut bacterium that knows exactly how to digest them. And the result, reported this week, was a drop in baby sniffles and coughs so big it made even the outside experts blink.

The experiment: breast milk’s best trick, in a bottle

Breast milk is packed with complex sugars called human milk oligosaccharides (HMOs) — the third most abundant solid in breast milk after lactose and fat — that babies can’t even digest. Their gut bacteria can. One bacterium in particular, Bifidobacterium infantis (B. infantis), thrives on HMOs, fermenting them into short-chain fatty acids that appear to help the immune system respond to viruses and bacteria. Yet many babies in Western countries seem to lack B. infantis in their guts.

Petter Brodin’s team at the Karolinska Institutet closed that gap with a synbiotic — seven HMOs plus B. infantis strain LMG11588 mixed into formula powder — and ran a randomized, double-blind trial: about half of the 223 babies drank the synbiotic formula, the rest the same formula without it. Parents didn’t know which was which, logging every sneeze, cough, and runny nose until the babies turned 6 months old.

The numbers: fewer infections, faster recoveries

By 6 months, just 23% of the babies on the synbiotic formula had developed a respiratory infection, versus 40% on plain formula — a relative reduction of more than 40%. And when supplemented babies did catch something, they recovered a few days faster on average.

Stool samples matched the symptom diaries: near-universal colonization with B. infantis (versus less than 10% in controls), lower gut inflammation, higher secretory IgA, and calmer systemic inflammation. The researchers suggest the synbiotic dampened inflammatory responses to the everyday microbes babies constantly meet.

Daniel Davis, an immunologist at Imperial College London who wasn’t involved in the study, called the results “phenomenally exciting.” Early-life infections have been linked to more severe infections and higher allergy risk later in childhood, so a formula that helps set up healthier immune development is, as he put it, “a really powerful concept.”

The catch: why this isn’t a formula run just yet

A few caveats. First, the funding: Nestlé, a formula giant, paid for the trial, and several co-authors are Nestlé employees. The academic authors say they had full data access and final say on publication — but the industry tie is worth knowing.

Second, this is one trial in one country. Davis says larger studies across more countries and longer follow-up are needed, and warns revving up an infant’s immune response could have unintended consequences, including higher allergy or autoimmunity risk. The formula is also experimental (trial NCT06073652), with findings shared ahead of peer review at a Royal Society conference on October 12. Promising, yes. Proven, no.

A Canadian footnote: the HMO half of this synbiotic is already cleared in Canada — Health Canada approved 2′-fucosyllactose, the most abundant HMO, for infant formula years ago, noting it feeds gut bacteria and may support immune modulation in infants. The sugar is already here; the live-bacteria pairing is the new frontier.

What are probiotics and how are they supposed to work?

Probiotics are live microorganisms — mostly bacteria from the Lactobacillus and Bifidobacterium families, sometimes yeasts like Saccharomyces boulardii — found in yogurt, other fermented foods, and dietary supplements.

Researchers think they may work by maintaining a healthy community of gut microbes, producing useful substances like short-chain fatty acids, and influencing the immune response — the mechanism the baby trial tapped into.

Benefits run strain by strain: if one specific Lactobacillus strain helps with something, that says nothing about another strain of the same species. That’s why the trial names the exact strain (B. infantis LMG11588), not just the species. And probiotics and prebiotics aren’t the same thing — prebiotics are the indigestible food components that feed desirable microbes, and a product combining both is called a synbiotic.

What are the side effects of probiotics?

For most healthy adults, probiotics are well tolerated — side effects are usually mild and digestive, like gas or bloating, and tend to fade. That said, they aren’t risk-free for everyone.

The serious caution: severe or even fatal infections have been reported in premature infants given probiotics, prompting an FDA warning to healthcare providers. People with weakened immune systems, serious illness, or central venous catheters should talk to a doctor before using probiotics.

Probiotics may also interact with certain medications, including immunosuppressants and some antifungals — check with a pharmacist or doctor if you take prescription drugs. And one firm line: nothing in this research is a reason to change an infant’s diet on your own. That’s a pediatrician conversation, full stop.

How much probiotics should you take?

There is no one right dose — studies use widely different amounts depending on the strain and outcome, so bigger CFU numbers on a label don’t automatically mean better. The honest approach: look for the dose used in human studies of that exact strain and follow it. If a label hides its strains and doses behind a “proprietary blend,” you’re buying blind. A pharmacist or doctor can help match a product to your situation.

What should you look for on the label?

What separates a serious product from a hopeful one:

Full strain identification. The label should name the genus, species, and the alphanumeric strain code — e.g. Lactobacillus rhamnosus GG or Bifidobacterium infantis LMG11588. “Contains probiotics” without strain details tells you nothing, because effects are strain-specific.

A valid NPN. In Canada, probiotics sold as natural health products need an 8-digit Natural Product Number from Health Canada. No NPN means no Health Canada review of the product’s safety, quality, and claims.

CFU guaranteed at expiry, not at manufacture. Live organisms die off over time. A reputable label states the colony-forming units you’re actually getting through the expiry date, not just the number that went into the bottle on day one.

Third-party testing and honest packaging. Look for independent verification of contents and clear storage instructions (some strains need refrigeration). If the company won’t say exactly what’s in each capsule, shop elsewhere.

This article reports on recent health research and is for general information only — it isn’t medical advice and doesn’t replace your doctor, pharmacist, or another qualified professional. Study findings describe what researchers observed, not a promise of results, and nothing here claims any supplement can diagnose, treat, cure, or prevent a disease. These statements have not been evaluated by Health Canada. Check with a healthcare professional before starting any new supplement, especially if you’re pregnant, nursing, taking medication, or managing a health condition.