Benefits
Infant colic relief (DSM 17938)
L. reuteri DSM 17938 has the strongest single-strain evidence for colic relief in breastfed infants. A 2018 individual patient data meta-analysis of 4 RCTs (345 infants) found 10^8 CFU/day reduced crying time by 27 minutes/day at 3 weeks — equivalent to a clinically meaningful effect. Recommended in pediatric guidelines as evidence-based first-line treatment for breastfed-infant colic. Less consistent benefit in formula-fed infants.
Cholesterol reduction (NCIMB 30242)
L. reuteri NCIMB 30242 has FDA-recognized cholesterol-lowering effects via bile salt hydrolase activity. A 9-week RCT (114 hypercholesterolemic adults) showed 2.9 billion CFU/day reduced LDL cholesterol by 11.6%, total cholesterol by 9.1%, non-HDL by 11.0%, and apolipoprotein B-100 by 8.4% vs. placebo. Comparable to mild statin therapy. Approved as a heart-health functional food ingredient.
Oral health: gingivitis and dental caries reduction
L. reuteri ATCC PTA 5289 delivered as lozenge significantly reduces plaque accumulation, gingivitis (improved Gingival Index by 30–60%), and Streptococcus mutans counts in caries-active children. Multiple meta-analyses confirm short-term oral L. reuteri lozenge use as effective adjunct to oral hygiene.
Functional constipation in children
Multiple RCTs show L. reuteri DSM 17938 significantly improves bowel frequency in children with functional constipation. Particularly effective in conjunction with osmotic laxatives. May serve as alternative for children intolerant to PEG 3350.
Mechanism of action
Reuterin production — broad-spectrum antimicrobial
L. reuteri uniquely produces reuterin (3-hydroxypropionaldehyde) from glycerol metabolism. Reuterin is broad-spectrum antimicrobial, active against gram-positive and gram-negative bacteria, fungi, protozoa, and viruses. This is a strain-defining mechanism not shared by any other probiotic species. Particularly effective against Helicobacter pylori, E. coli, and Clostridium species.
Bile salt hydrolase for cholesterol reduction
L. reuteri NCIMB 30242 has exceptionally robust bile salt hydrolase (BSH) activity. Deconjugated bile acids are excreted, forcing the liver to synthesize new bile acids from cholesterol via CYP7A1 — reducing serum LDL. The resulting cholesterol reduction is comparable to a low-dose statin.
Vagal nerve modulation for gut motility
L. reuteri DSM 17938 improves gut motility partly via vagal nerve afferent signaling. The mechanism for colic relief involves increased anti-inflammatory cytokines, reduced intestinal pain perception, and modulation of intestinal mast cell activity.
Vitamin B12 and folate production
L. reuteri is among the few human-origin lactobacilli that produce significant B12 (cobalamin) and folate. While bioavailability of bacterial B12 to the host is limited (most synthesized in the colon), this nutritional contribution may have systemic relevance.
Clinical trials
Individual patient data meta-analysis of 4 randomized, double-blind, placebo-controlled trials of L. reuteri DSM 17938 in infants with colic. (Sung et al. 2018, Pediatrics)
Pooled across 4 RCTs, 345 infants.
L. reuteri DSM 17938 (10^8 CFU/day for 21-28 days) significantly reduced crying duration vs placebo. AT 21 days: treatment success rate 39.6% vs 17.1% placebo. Critical context: efficacy applies to breastfed infants only — not formula-fed (where L. reuteri DSM 17938 has not shown benefit). Cochrane 2019 review and ESPGHAN endorse for breastfed colicky infants. The strain-specific evidence is among the strongest in pediatric probiotic literature.
9-week, randomized, double-blind, placebo-controlled trial in 127 hypercholesterolemic adults receiving yogurt with L. reuteri NCIMB 30242 (2.9 billion CFU/day) vs placebo yogurt. (Jones et al. 2012, Eur J Clin Nutr)
127 hypercholesterolemic adults. 9-week intervention.
LDL cholesterol reduced 11.6%, total cholesterol 9.1%, non-HDL 11.0%, apoB-100 8.4% vs placebo. Mechanism via bile salt hydrolase activity (deconjugates bile acids, increases hepatic cholesterol use for new bile synthesis). Industry-funded (Micropharma). Note: statins reduce LDL 30-60% — first-line for high CV risk; probiotics adjunctive for low-moderate risk preferring natural approaches.
Randomized, double-blind, placebo-controlled trial in subjects with moderate-to-severe gingivitis receiving L. reuteri ATCC PTA 5289 + L. reuteri DSM 17938 lozenges vs placebo. (Krasse et al. 2006, or Iniesta et al. 2012, J Clin Periodontol)
Adults with gingivitis.
Reductions in plaque index (~46%), gingival index (~58%), bleeding on probing (~61%), pocket depth (~22%). Mechanism via reuterin (an antimicrobial compound) and biofilm modulation. Note: standard oral hygiene (brushing, flossing, professional cleaning) remains foundational; probiotic lozenges adjunctive.