The primary purpose of this randomized, double-blinded, placebo-controlled, crossover clinical trial is to evaluate the efficacy of dietary supplementation with Bifidobacterium infantis NLS super strain among celiac disease patients on a gluten-free who have persistent gastrointestinal symptoms.

Most patients with celiac disease demonstrate substantial clinical improvement during the first few weeks after the onset of the consumption of a gluten-free diet. However, between 30-50% of patients with celiac disease have persistent gastrointestinal symptoms despite consuming a gluten-free diet and presenting negative antibodies. It has recently been reported that celiac disease patients treated with a gluten-free diet that still have persistent symptoms possess different intestinal microbiota patterns than patients without persistent symptoms. Furthermore, a pilot study showed that dietary supplementation with probiotics (Bifidobacterium infantis NLS super strain - Natren LIFESTART®) in untreated celiac disease patients was associated with a significant improvement in symptoms as compared to placebo. Collectively, these findings contribute to the hypothesis that celiac disease patients on a gluten-free diet in whom gastrointestinal symptoms persist may benefit from the supplementation of Bifidobacterium infantis NLS super strain.

Participants in this double-blinded crossover trial will be randomized to receive either placebo or Bifidobacterium infantis NLS super strain for 3 weeks, followed by a 2 week washout period, and then followed by 3 weeks of the other of either placebo or probiotic supplementation.

Inclusion Criteria:

• Men or women at least 18 years of age
• Precise diagnosis of celiac disease: serology (a-tTG IgA and/or DGP IgG and/or EmA) and histology (Marsh IIIa or greater) concordantly positive, confirmed at investigator's institution
• Consuming a gluten-free diet for at least 2 years
• Persistent gastrointestinal symptoms: global GSRS questionnaires ≥2 or ≥ 3 points for any of the 5 sub-dimensions
• Signature of informed consent

Exclusion Criteria:

• Patients not interested or unable to comply with questionnaires and collection of samples of blood, feces, and urine
• Complicated celiac disease (refractory, ulcerative jejunoileitis, lymphoma)
• Concomitant pathologies that are uncompensated or untreated (Type I or II diabetes mellitus, hyperthyroidism, hypothyroidism, diarrhea due to bile salts, pancreatic insufficiency, bacterial overgrowth)
• Consumption within the 2 weeks prior to study enrollment of medication that interferes with bowel functioning (antibiotics, NSAIDs, laxatives, metformin, opiates, anticholinergics [atropine, antidepressants, neuroleptics, antipsychotics, antiparkinsonians], anticonvulsants, antihistamines, antihypertensives [calcium antagonists, clonidine, diuretics, metal ions (aluminum), antacids, sucralfate, barium sulfate, bismuth, calcium, iron, heavy metals (arsenic, lead, mercury)], resins (cholestyramine), or any other medication deemed relevant by the investigator).
• Women that are pregnant or may become pregnant during the study