Probiotic Lactobacillus reuteri for infant colic - dosage and evidence
Probiotic Lactobacillus reuteri for infant colic: dosage and evidence in the table. u Bucha.
Infant colic affects 10 to 40% of children in the first months of life and is one of the most common reasons for pediatric visits during this period (Sung et al., BMJ, 2014). In the sea of home remedies - dill, massages, special mixtures - one bacterial strain has gathered a solid evidence base from randomized clinical trials: Lactobacillus reuteri DSM 17938. A meta-analysis of six RCTs published in Pediatrics showed that L. reuteri significantly reduces crying time in infants with colic compared to placebo (Sung et al., Pediatrics, 2014). This article explains what dosages were used, who benefits the most, and what we still don't know.
KEY INFORMATION
• A meta-analysis of 6 RCTs confirmed the effectiveness of L. reuteri DSM 17938 in reducing crying time in colic (Sung et al., Pediatrics, 2014).
• Dosage used in studies: 10^8 CFU (100 million) once daily for 21-28 days.
• The effect is stronger in breastfed infants than in formula-fed ones.
• The Cochrane review (2018) confirms the effect but points out the heterogeneity of studies.
• The DSM 17938 strain matters - other strains of L. reuteri do not have the same evidence base.
What is infant colic and why is it so difficult to treat?
Infant colic is defined by the Wessel criteria: crying lasting more than 3 hours a day, more than 3 days a week, for more than 3 weeks in a healthy, well-nourished child (Wessel et al., Pediatrics, 1954). This is the classic definition, although newer clinical positions allow for modifications. Colic usually resolves spontaneously before the 4th month of life, which complicates the assessment of treatment effectiveness - it is difficult to distinguish the effect of therapy from natural remission.
Why is treating colic difficult? The causes are not fully understood. Hypotheses include: immaturity of the gut nervous system, disturbances in gut microbiota, hypersensitivity to cow's milk proteins, lactose intolerance, and many others. This multifactorial nature means that no single intervention works for all children. L. reuteri addresses a specific mechanism - modulation of gut microbiota - and therefore is not a "cure for colic," but an intervention aimed at a subgroup of children with dysbiosis as the cause of symptoms.
How L. reuteri reduces colic symptoms - mechanism of action
L. reuteri DSM 17938 operates through several overlapping mechanisms. Firstly - it secretes reuterin (3-hydroxypropionaldehyde), a compound with antibacterial properties that selectively inhibits gut pathogens without harming healthy microbiota (Shornikova et al., Acta Paediatrica, 1997). Secondly - it accelerates the motility of the small intestine, which reduces the time gas remains in the intestines and the associated discomfort.
Thirdly, and perhaps most importantly - L. reuteri modulates the gut-brain axis through neural (vagus nerve) and immune signals. Studies in animal models have shown that colonization by L. reuteri affects the expression of visceral pain receptors and may reduce neuropathic hypersensitivity in the gut. For parents observing colic: a child with colic is truly in pain - it is not a matter of temperament or upbringing.
We have noticed that parents find it difficult to assess whether L. reuteri "works," because the reference point - "how much they normally should cry" - does not exist. Clinical studies measure crying time in minutes per day, recorded daily by caregivers. If you decide to try this probiotic, start keeping a crying diary from day one - without this, after a month, it is unclear whether there was any improvement.
Dosage table for L. reuteri in infant colic studies
The table below compares the dosing parameters used in key published studies. The doses listed below do not constitute medical advice - the decision to use a probiotic in an infant should be consulted with a pediatrician.
| Study / source | Strain | Dose CFU/day | Form | Duration | Main outcome |
|---|---|---|---|---|---|
| Savino et al. (2010) | L. reuteri DSM 17938 | 10^8 (100 million) | Oil drops | 21 days | Reduction of crying by ~50 min/day after 7 days; ~60+ min after 21 days |
| Sung i in. (2014) - metaanaliza 6 RCT | L. reuteri DSM 17938 | 10^8 | Drops | 21-28 dni | Significant reduction in crying time vs placebo; stronger effect in breastfed infants |
| Cochrane (2018, review) | L. reuteri DSM 17938 and others | 10^8 | Drops | 21-28 dni | Effect confirmed, but heterogeneity of studies; caution with formula milk |
| Szajewska et al. (2013) | L. reuteri DSM 17938 | 10^8 | Drops | 28 days | Significant reduction in crying in breastfed infants; no effect in formula-fed infants |
| Conclusion: A dose of 10^8 CFU of L. reuteri DSM 17938 once daily for 21-28 days is the only regimen with a solid evidence base. Other strains or doses do not have comparable research support in infant colic. | |||||
It should be emphasized that studies on infant colic are methodologically challenging - blinding is limited (taste, smell), and the endpoint is the subjective assessment of parents (crying diary). This does not devalue the results but requires treating them with appropriate caution. A meta-analysis of 6 RCTs is, however, a solid foundation for a relatively niche pediatric topic.
Does L. reuteri work the same way in formula-fed children?
This is one of the key questions, as the answer is not straightforward. Early studies by Savino et al. (2007, 2010) focused almost exclusively on breastfed infants and showed a clear effect (Savino et al., Pediatrics, 2007). Szajewska's studies (2013) conducted in Poland on infants fed both breast milk and formula showed a significant reduction in crying only in the breastfed group.
Why the difference? The hypothesis is that the gut microbiota of breastfed infants is more "open" to colonization by new strains because colostrum and breast milk contain prebiotics (HMO - human milk oligosaccharides) that support the growth of beneficial bacteria. Formula milk, even when fortified, has a different prebiotic spectrum. L. reuteri may find it harder to implant in the intestines of infants on formula.
This does not mean that trying it on a formula-fed child is pointless - some studies suggest an effect, albeit weaker. But expectations should be calibrated accordingly. If after 3 weeks of administering L. reuteri you see no change, and the child is on formula, it is possible that this intervention simply may not be sufficient in your case.
We have noticed in the literature analyses that pediatricians in Poland are increasingly mentioning L. reuteri as one of the options for colic, but they rarely explain to parents the difference between strains. Buying "any L. reuteri" instead of specifically DSM 17938 is a mistake - the evidence pertains only to one strain and cannot be directly transferred to others.
What else can help with colic - clinical context
L. reuteri is not the only evidence-based approach. A 2013 Cochrane review assessed several interventions. A maternal diet excluding cow's milk protein may help children with milk protein allergies - this is a separate mechanism from microbiota. Fennel (fennel tea) showed effects in small studies, but the methodological quality of these studies is low.
Simethicone (over-the-counter gas relief) is a popular choice among parents, but systematic reviews do not confirm its superiority over placebo in infant colic. Abdominal massage has weak but positive data - and is completely safe, making it a reasonable complement to pharmacological and probiotic interventions.
The most important clinical conclusion: no single intervention works for all children. A gradual approach - from eliminating maternal diets when allergy is suspected, through massage, to L. reuteri - offers a chance to identify the causative factor. A pediatrician should be involved in this process, especially when colic is severe or when the child is not gaining weight.
Preventive use of L. reuteri - does it make sense before colic appears?
Most studies focused on therapeutic intervention: L. reuteri was given to infants who already had colic. However, there is also data on preventive use - administering L. reuteri from the first days of life, before colic develops. A study by Romano et al. from 2014 showed that breastfed infants who received L. reuteri DSM 17938 preventively from birth cried significantly less in the third month of life than the placebo group (Romano et al., Journal of Paediatrics and Child Health, 2014).
Such an approach is not yet standard in clinical recommendations - the data is promising, but the evidence base is narrower than for therapeutic use. From a practical point of view: if an older child in the family had severe colic, or if a breastfeeding mother wants to take preventive measures, discussing the early introduction of L. reuteri DSM 17938 with a pediatrician is justified. The safety profile is unquestionable, and the potential benefit is real.
Storage and practical aspects of using drops
Biogaia Protectis - the most widely studied carrier of L. reuteri DSM 17938 - is an oil drop product that requires refrigeration after opening. Live bacteria are sensitive to heat; exceeding the storage temperature may reduce the number of viable cells below the declared dose. A few practical tips for parents: drops should be given just before or during feeding - breast milk acts as a prebiotic supporting the implantation of the strain. Do not mix drops with hot milk or tea - temperatures above 40°C destroy the bacteria.
Shake the bottle before each use, as the bacteria settle in the oil. If the child spits out a drop or vomits immediately after administration - do not give an additional dose on the same day; wait until the next feeding. The duration of use in studies was 21-28 days; continuing beyond 28 days is not contraindicated, but there is no data confirming additional benefits from longer use for colic. If colic has resolved, it can be discontinued - there is no need for gradual withdrawal.
We have noticed that parents often find it difficult to assess whether the product they purchased contains the DSM 17938 strain. The label should clearly state the strain name and the number of CFUs per dose (usually 5 drops = 10^8 CFU). If the manufacturer only states "Lactobacillus reuteri" without the strain number and without specifying CFUs - you cannot be sure that you are buying a product corresponding to what was clinically studied.
Frequently Asked Questions
What dose of L. reuteri is used in studies of infant colic?
In the vast majority of clinical studies, 10^8 CFU (100 million live cells) of L. reuteri DSM 17938 were administered once daily for 21-28 days (Sung et al., Pediatrics, 2014). Other strains and doses do not have the same evidence base. The DSM 17938 strain and the exact dose are crucial when choosing a specific preparation.
Does L. reuteri work only for breastfed infants?
Early studies mainly included breastfed infants, and the effects were strongest there. The 2018 Cochrane review included both groups - the effect was observed in both, but was weaker and less consistent with formula feeding. This is important information when planning interventions, not a prohibition on use.
When can L. reuteri be given to an infant?
Most studies concerned infants from the first week of life. L. reuteri DSM 17938 is considered safe for healthy term newborns. Before giving any probiotic to a newborn, consult with a pediatrician, especially in cases of prematurity, immune system disorders, or antibiotic use.
How long does it take for improvement after administering L. reuteri?
Clinical studies reported a significant reduction in crying time as early as 7 days after the first dose. The full effect was assessed after 21-28 days. In the meta-analysis by Savino (2010), crying time decreased by about 50 minutes per day in the first week and by over 60 minutes per day after the third week of L. reuteri use vs placebo.
Is L. reuteri safe for infants?
L. reuteri DSM 17938 has a good safety profile confirmed in many clinical studies. The Cochrane review (2018) did not report any serious adverse events in the analyzed studies. As with any supplement for infants, the decision to administer should be approved by a pediatrician, especially in cases of prematurity or congenital diseases (Sung et al., 2014).
Can L. reuteri be used preventively - before colic appears?
Preventive studies (administering from the first days of life) are promising, especially in breastfed infants. Romano et al. (2014) demonstrated a significantly shorter crying time in the 3rd month of life in infants receiving L. reuteri DSM 17938 from birth vs placebo. Preventive use is not yet a standard in clinical recommendations, but it may be considered after consulting with a pediatrician, especially if older siblings had severe colic (Romano et al., 2014).
This article is for informational and educational purposes and does not replace consultation with a doctor. If you are pregnant, breastfeeding, taking medications, or have chronic conditions, consult the use of supplements or herbs with a specialist.
Author: Michał Waluk · Published: 2026-05-04 · Updated: 2026-05-04
