Background Early probiotic supplementation influences infant immune development, but effects on specific immune biomarkers remain unclear. Methods We searched six databases (2000–2025) for randomised controlled trials of oral probiotic supplementation initiated before 2 years of age that reported faecal secretory IgA (sIgA) and/or cytokines. For sIgA, quantitative synthesis was restricted to healthy full-term infants. Random-effects meta-analyses were conducted for outcomes reported as means, and a quantile-estimation approach was applied to studies reporting medians. Risk of bias was assessed using the RoB 2 tool. Results Thirty-nine randomised controlled trials met the inclusion criteria. Twenty-four trials reported sIgA, 18 reported cytokines, and three reported both outcomes. Seven sIgA trials in healthy full-term infants (440 probiotic, 414 control) were meta-analysed. Probiotic supplementation was associated with higher faecal sIgA, with a pooled mean difference of 435 µg/g stool (95% CI 196–674; I² = 0%). Larger effects were observed when supplementation began at or before 4 weeks of age. Cytokine outcomes were derived from a broader, clinically heterogeneous evidence base, and pooled analyses showed no consistent effects. Conclusion Probiotic supplementation in healthy full-term infants is associated with higher faecal sIgA, whereas effects on cytokine outcomes remain uncertain. Impact <UnorderedList Mark="Bullet"> <ItemContent> Probiotic supplementation was associated with higher faecal sIgA in healthy full-term infants, with a pooled mean difference of 435 µg/g stool (I2 = 0%) </ItemContent> <ItemContent> The pooled sIgA estimate favoured probiotics and remained similar in sensitivity analyses. </ItemContent> <ItemContent> Earlier initiation ( ≤ 4 weeks) was associated with larger sIgA effects than later initiation. </ItemContent> <ItemContent> Cytokine outcomes were derived from more clinically heterogeneous populations, and pooled analyses did not show consistent effects. </ItemContent> <ItemContent> Faecal sIgA may be a practical immunological endpoint for mechanistic infant probiotic trials. </ItemContent> </UnorderedList>

Probiotic supplementation is associated with higher faecal secretory IgA (sIgA) in healthy full-term infants: a systematic review and meta-analysis

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2026年5月22日

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Yihenew Million Yeshtila,
Nerissa Bowcock,
Steven Leach

摘要

Background

Early probiotic supplementation influences infant immune development, but effects on specific immune biomarkers remain unclear.

Methods

We searched six databases (2000–2025) for randomised controlled trials of oral probiotic supplementation initiated before 2 years of age that reported faecal secretory IgA (sIgA) and/or cytokines. For sIgA, quantitative synthesis was restricted to healthy full-term infants. Random-effects meta-analyses were conducted for outcomes reported as means, and a quantile-estimation approach was applied to studies reporting medians. Risk of bias was assessed using the RoB 2 tool.

Results

Thirty-nine randomised controlled trials met the inclusion criteria. Twenty-four trials reported sIgA, 18 reported cytokines, and three reported both outcomes. Seven sIgA trials in healthy full-term infants (440 probiotic, 414 control) were meta-analysed. Probiotic supplementation was associated with higher faecal sIgA, with a pooled mean difference of 435 µg/g stool (95% CI 196–674; I² = 0%). Larger effects were observed when supplementation began at or before 4 weeks of age. Cytokine outcomes were derived from a broader, clinically heterogeneous evidence base, and pooled analyses showed no consistent effects.

Conclusion

Probiotic supplementation in healthy full-term infants is associated with higher faecal sIgA, whereas effects on cytokine outcomes remain uncertain.

Impact

Probiotic supplementation was associated with higher faecal sIgA in healthy full-term infants, with a pooled mean difference of 435 µg/g stool (I² = 0%)

The pooled sIgA estimate favoured probiotics and remained similar in sensitivity analyses.

Earlier initiation ( ≤ 4 weeks) was associated with larger sIgA effects than later initiation.

Cytokine outcomes were derived from more clinically heterogeneous populations, and pooled analyses did not show consistent effects.

Faecal sIgA may be a practical immunological endpoint for mechanistic infant probiotic trials.