The question of whether probiotics need to be taken daily or could be effective taken every other day (or even less frequently) has been explored in research with mixed results.

1. Gut Colonization and Persistence:
   A study evaluating the persistence of Lactobacillus reuteri DSM17938 found that both daily and alternate-day supplementation resulted in similar levels of gut colonization¹. However, the probiotic count declined rapidly once supplementation was stopped, indicating that continuous intake is necessary for sustained colonization.

2. Dosing in Preterm Infants:
   In preterm infants, higher probiotic doses have been suggested to improve colonization by beneficial bacteria. However, studies have not shown significant effects on clinical outcomes with different dosing strategies².

3. Clinical Outcomes in Adults:
   A study assessing the effectiveness of multi-strain probiotics in adults with diarrhea-predominant irritable bowel syndrome (IBS-D) demonstrated that daily supplementation resulted in significant symptom improvement³. The research did not directly compare alternate-day dosing but implied the necessity of regular intake to maintain benefits.

4. Probiotics for Preventing Infections:
   Another study looked into the effects of probiotics taken every second day in neonates. It showed initial benefits that diminished over time, suggesting a transient yet significant short-term benefit⁴.

5. Necrotizing Enterocolitis Prevention:
   For preterm infants in NICUs, probiotics were administered daily or twice daily, indicating a preference for frequent dosing to achieve desired outcomes⁵.

In summary, the current body of evidence supports daily supplementation to maintain gut colonization and achieve consistent clinical benefits. Alternate-day dosing can still be effective, especially in maintaining gut colonization, but the benefits may decline more rapidly once supplementation stops. Therefore, continuous daily intake is generally recommended to sustain the probiotic effects¹³⁴⁵.

Footnotes

1. Tracey J. Smith, "Persistence of Lactobacillus reuteri DSM17938 in the human intestinal tract: response to consecutive and alternate-day supplementation," PubMed. ↩ ↩²

2. Chandra Rath, "Effect of Probiotic Dose Escalation on Gut Microbiota and Clinical Outcomes in Preterm Infants—A Systematic Review," PubMed Central. ↩

3. Barbara Skrzydło-Radomańska, "The Effectiveness and Safety of Multi-Strain Probiotic Preparation in Patients with Diarrhea-Predominant Irritable Bowel Syndrome," PubMed Central. ↩ ↩²

4. Dirk Olbertz, "Potential Benefit of Probiotic E. Coli Nissle in Term Neonates: A Multicentre Randomised Double Blind Controlled Trial," PubMed Central. ↩ ↩²

5. Julie Kutylowksi, "Types, Frequency, Duration, and Dosage of Probiotics to Prevent Necrotizing Enterocolitis in Preterm Infants Among Countries," PubMed. ↩ ↩²