The i3.1 probiotic was found to reduce symptoms of lactose intolerance safely and effectively but did not alter lactose hydrogen breath test (LHBT) results, according to an 8-week trial published in the Journal of Clinical Gastroenterology.

Patients (N=48) with lactose intolerance with LHBT ³20 parts per million and Symptoms Questionnaire for Lactose Malabsorption Screening score ³6 were recruited at the Hospital Juárez de México for this randomized, placebo-controlled, single-blind clinical trial. Patients were randomly assigned to receive 8 weeks of i3.1 (n=33) or placebo (n=15). Changes in symptoms from baseline were evaluated. The LHBT was assessed at 10 minutes before and 60, 120, and 180 minutes after ingestion of 25 g lactose.

The intervention and control cohorts were aged mean 39.1±13.0 and 44.4±18.3 years, 61% and 67% were women, mean body mass index was 25.9±4.0 and 28.2±5.2 kg/m2, and total symptom scores were 10.0±2.4 and 8.7±1.5 points, respectively.

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At 8 weeks, the change from baseline in symptom scores were -5.11±2.97 points among the probiotic and -1.00±1.84 points among the placebo recipients (P <.001).

For symptom subscores, the probiotic recipients had decreased scores for flatulence (P =.004) and abdominal pain (P =.045). The area under the curve for LHBT scores was significantly reduced among the probiotic recipients (P =.019) but there was no group difference compared with placebo (P =.621).

Most patients did not report any adverse events (87.9% vs 80.0%); 1 event was reported by 9.1% and 13.3% and 2 events by 3.0% and 6.7% in the intervention and placebo cohorts, respectively. Adverse events included abdominal distension (n=7), headache (n=2), abdominal pain (n=2), and nausea (n=1).

This study was limited by its reliance on self-reported symptom outcomes.

These data indicate that the probiotic i3.1 may be effective and safe for reducing patient-reported symptoms of lactose intolerance, which may indicate a more pronounced effect on visceral sensitivity than lactose degradation itself.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Cano-Contreras AD, Alfaro IJM, López VMM, et al. Efficacy of i3.1 probiotic on improvement of lactose intolerance symptoms: a randomized, placebo-controlled clinical trial. J Clin Gastroenterol. 2022;56(2):141-147. doi:10.1097/MCG.0000000000001456