LGG and Respiratory Infections in Day Care Children

A randomised, double-blind trial of Lactobacillus rhamnosus GG in 281 day care children in Zagreb, Croatia, found that LGG reduced the risk of upper respiratory tract infections, especially those lasting longer than three days. It did not reduce lower respiratory or gastrointestinal infections. The results are promising but come from one setting and one winter.

Why study probiotics in day care?

Children in group care get more infections than children cared for at home, because of close contact and shared surfaces. The gut contains much of the body's immune tissue, which gives a reason to test whether gut-acting probiotics influence infections elsewhere in the body. LGG, as the best-studied probiotic, was a natural candidate.

How was the trial designed?

Researchers led by Iva Hojsak, with Hania Szajewska as a co-author, published the trial in Clinical Nutrition. It enrolled 281 children, 139 in the LGG group and 142 in the placebo group, attending day care centres in Zagreb.

The LGG group received 1 billion CFU of LGG in 100 mL of fermented milk, and the control group received the same fermented milk without LGG. The study was randomised and double-blind. It lasted three months, from November to February, covering the high season for respiratory illness.

What were the results?

Upper respiratory tract infections. LGG significantly reduced the risk of these infections, and of infections that lasted more than three days. The number of days with respiratory symptoms was also reduced.

Lower respiratory tract infections. No significant reduction was seen.

Gastrointestinal infections. LGG did not significantly reduce gastrointestinal infections, vomiting, diarrhoea or days with gastrointestinal symptoms.

The respiratory finding is the main takeaway. The null gastrointestinal result is notable, since LGG is better known for gut effects. The authors noted that the winter timing missed the summer, when gastrointestinal infections peak.

What are the limitations?

Diagnoses depended on clinical judgement and parent or staff reporting. Severe infections were rare, so the study could not say much about serious illness. It was done in one city, with a fermented milk vehicle, and the dose was 1 billion CFU, lower than doses used for diarrhoea prevention. Results from one winter in one country may not apply elsewhere.

What do other studies show?

A pooled review of probiotics for respiratory infections in children and adults concluded that probiotics may modestly reduce the number of people who get a respiratory infection, but the certainty of evidence was low. Results differ by strain, dose, age and setting. LGG has been studied in other day care and hospital settings with variable results.

This pattern means LGG belongs among strains with a plausible, partially supported signal, and that no parent should expect a probiotic to prevent colds reliably .

Why would LGG affect respiratory infections?

Proposed mechanisms include changes in gut immune signalling, effects on antibody production and shifts in the microbiome that influence immune responses at distant mucosal sites. These ideas come mostly from laboratory and animal studies, and the trial did not measure them.

How does this fit with other LGG day care trials?

Another group has also tested LGG in day care children, and evidence from hospitals suggests that LGG may lower the risk of hospital-acquired gastrointestinal and respiratory infections. The results are not identical across settings, which is expected when infection rates, hygiene measures and seasons differ. The overall impression is a signal of possible benefit that has not been confirmed in large, independent trials.

Anyone reading a headline about a probiotic cutting infections should ask three questions. Was the strain named? Was the study blinded and placebo-controlled? Did other groups find the same result? The Zagreb trial passes the first two tests and awaits an answer on the third.

What should parents take from this?

First, there is a reasonable but not conclusive basis for LGG in reducing the length of respiratory infections in day care children. Second, the dose and formulation in the trial differ from a sachet, so the result describes the strain, not a specific product. Third, hand washing, vaccination, sleep, and keeping unwell children at home do the heavy lifting.

Rhamnosus GG Sachets from ELMED Life Sciences provide LGG ATCC 53103 at 6 billion CFU per sachet. For the overall evidence by condition, see the guide to LGG probiotic sachets. For children with frequent or severe infections, poor growth or unusual infections, a doctor's assessment is needed.