Ning Dai

Prevalence and Presentation of Lactose Intolerance and Effects on Dairy Product Intake in Healthy Subjects and Patients With Irritable Bowel Syndrome

BACKGROUND & AIMSnThe effects of lactase deficiency on digestive symptoms and diet in patients with irritable bowel syndrome (IBS) have not been well defined. We assessed lactose absorption and tolerance and the intake of dairy products in healthy volunteers (controls) and patients with diarrhea-predominant IBS (D-IBS).nnnMETHODSnSixty patients diagnosed with D-IBS at the Sir Run Run Shaw Hospital, Hangzhou, China and 60 controls were given hydrogen breath tests to detect malabsorption and intolerance after administration of 10, 20, and 40 g lactose in random order 7-14 days apart; participants and researchers were blinded to the dose. We assessed associations between the results and self-reported lactose intolerance (LI).nnnRESULTSnMalabsorption of 40 g lactose was observed in 93% of controls and 92% of patients with D-IBS. Fewer controls than patients with D-IBS were intolerant to 10 g lactose (3% vs 18%; odds ratio [OR], 6.51; 95% confidence interval [CI], 1.38-30.8; P = .008), 20 g lactose (22% vs 47%; OR, 3.16; 95% CI, 1.43-7.02; P = .004), and 40 g lactose (68% vs 85%; OR, 2.63; 95% CI, 1.08-6.42; P = .03). H(2) excretion was associated with symptom score (P = .001). Patients with D-IBS self-reported LI more frequently than controls (63% vs 22%; OR, 6.25; 95% CI, 2.78-14.0; P < .001) and ate fewer dairy products (P = .040). However, self-reported LI did not correlate with results from hydrogen breath tests.nnnCONCLUSIONSnThe risk of LI is related to the dose of lactose ingested and intestinal gas production and is increased in patients with D-IBS. Self-reported LI, but not objective results from hydrogen breath tests, was associated with avoidance of dairy products.

Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

Lactose intolerance related to primary or secondary lactase deficiency is characterized by abdominal pain and distension, borborygmi, flatus, and diarrhea induced by lactose in dairy products. The biological mechanism and lactose malabsorption is established and several investigations are available, including genetic, endoscopic and physiological tests. Lactose intolerance depends not only on the expression of lactase but also on the dose of lactose, intestinal flora, gastrointestinal motility, small intestinal bacterial overgrowth and sensitivity of the gastrointestinal tract to the generation of gas and other fermentation products of lactose digestion. Treatment of lactose intolerance can include lactose-reduced diet and enzyme replacement. This is effective if symptoms are only related to dairy products; however, lactose intolerance can be part of a wider intolerance to variably absorbed, fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). This is present in at least half of patients with irritable bowel syndrome (IBS) and this group requires not only restriction of lactose intake but also a low FODMAP diet to improve gastrointestinal complaints. The long-term effects of a dairy-free, low FODMAPs diet on nutritional health and the fecal microbiome are not well defined. This review summarizes recent advances in our understanding of the genetic basis, biological mechanism, diagnosis and dietary management of lactose intolerance.

Bloating and distention in irritable bowel syndrome: the role of gas production and visceral sensation after lactose ingestion in a population with lactase deficiency.

OBJECTIVES:Bloating and distention are often attributed to dietary factors by patients with irritable bowel syndrome (IBS). This study examined the effects of gas production and visceral hypersensitivity on digestive symptoms after lactose ingestion in a population with lactase deficiency.METHODS:IBS patients (n=277) and healthy controls (HCs, n=64) underwent a 20-g lactose hydrogen breath test (LHBT) with evaluation of hydrogen gas production and lactose intolerance (LI) symptoms. Abdominal distention (199 IBS, 40 HCs) was measured during LHBT. Rectal sensitivity (74 IBS, 64 HCs) was assessed by barostat studies.RESULTS:Hydrogen production and distention were similar in IBS patients and HCs during LHBT; however, LI was more frequent in IBS (53.8 vs. 28.1%, P<0.001), especially bloating (39.0% vs. 14.1%, P<0.001) and borborygmi (39.0 vs. 21.9%, P=0.010). Only 59.0% of patients with bloating had distention. No correlation was observed between girth increment and bloating (P=0.585). IBS patients had lower rectal sensory thresholds (P=0.001). Multivariate analysis indicated that hydrogen production increased bloating (odds ratio (OR) 2.19, 95% confidence interval (CI) 1.09–4.39, P=0.028) and borborygmi (OR 12.37, 95% CI 3.34–45.83, P<0.001) but not distention (P=0.673). Visceral hypersensitivity was associated with bloating (OR 6.61, 95% CI 1.75–25.00, P=0.005) and total symptom score (OR 3.78, 95% CI 1.30–10.99, P=0.014).CONCLUSIONS:Gas production and visceral hypersensitivity both contribute to digestive symptoms, especially bloating and borborygmi, in IBS patients after lactose ingestion. Objective abdominal distention is not correlated with subjective bloating.

Lactose intolerance in irritable bowel syndrome patients with diarrhoea: the roles of anxiety, activation of the innate mucosal immune system and visceral sensitivity

Irritable bowel syndrome patients with diarrhoea (IBS‐D) often report intolerance to milk; however, the mechanism underlying these symptoms is unknown.

Lactose intolerance in patients with chronic functional diarrhoea: the role of small intestinal bacterial overgrowth

Aliment Pharmacol Theru200231, 892–900

A study of the methodological and clinical validity of the combined lactulose hydrogen breath test with scintigraphic oro‐cecal transit test for diagnosing small intestinal bacterial overgrowth in IBS patients

Small intestinal bacterial overgrowth (SIBO) may be a cause of irritable bowel syndrome (IBS); however, current investigations have important limitations. We aimed to identify clinically relevant diagnostic criteria for SIBO based on lactulose hydrogen breath test (LHBT) alone and combined with scintigraphic measurement of oro‐cecal transit (SOCT).

Self-reported lactose intolerance in clinic patients with functional gastrointestinal symptoms: prevalence, risk factors, and impact on food choices

Many patients complain of abdominal symptoms with dairy products; however, clinical and psychosocial factors associated with self‐reported lactose intolerance (SLI) have not been assessed in large studies. In particular, data are lacking from lactase deficient populations. This prospective cohort study assessed the prevalence of, and risk factors for, SLI in Chinese patients attending a gastroenterology clinic.

Micro-inflammation in functional dyspepsia: A systematic review and meta-analysis

Functional dyspepsia (FD) is a gastrointestinal disorder of unknown etiology. Although micro‐inflammation appears to be important in the pathogenesis, studies evaluating immune activation in FD have been inconsistent. A systematic review of literature and meta‐analysis was performed to compare immunologic cell counts and cytokine levels in the mucosa and peripheral blood of individuals with FD and healthy controls. PubMed, Embase, and the Cochrane library were searched. Data on immunologic cell counts and cytokines levels among individuals with FD and control groups were extracted and compared by calculating standard mean differences (SMD). Thirty‐seven studies met the inclusion criteria. Mast cell (SMD = 0.94, 95%CI 0.26‐1.62, P = .007) and eosinophil counts (SMD = 0.36, 95%CI 0.06‐0.68, P = .03) in the stomach were increased, among individuals with FD compared to controls. Similarly, mast cell (SMD = 0.66, 95%CI 0.20‐1.13, P = 0.005) and eosinophil (SMD = 0.95, 95%CI 0.66‐1.24; P < .001) counts in the duodenum were also increased in those with FD compared to controls. In a subgroup analysis, elevated eosinophil counts in the duodenum were observed in both post‐prandial distress syndrome (SMD = 0.97, 95%CI 0.46‐1.47, P = .0002) and epigastric pain syndrome subtypes (SMD = 1.16, 95%CI 0.48‐1.83, P = .0008). No differences in mucosal intraepithelial lymphocyte, enterochromaffin cell, and neutrophil counts, as well as, peripheral interlukin‐6 (IL‐6) and IL‐10 levels were observed among individuals with FD and controls. Micro‐inflammation in the form of local immune cell infiltration, particularly eosinophils and mast cells, characterizes the pathogenesis of FD.

Four-sample lactose hydrogen breath test for diagnosis of lactose malabsorption in irritable bowel syndrome patients with diarrhea

AIMnTo validate 4-sample lactose hydrogen breath testing (4SLHBT) compared to standard 13-sample LHBT in the clinical setting.nnnMETHODSnIrritable bowel syndrome patients with diarrhea (IBS-D) and healthy volunteers (HVs) were enrolled and received a 10 g, 20 g, or 40 g dose lactose hydrogen breath test (LHBT) in a randomized, double-blinded, controlled trial. The lactase gene promoter region was sequenced. Breath samples and symptoms were acquired at baseline and every 15 min for 3 h (13 measurements). The detection rates of lactose malabsorption (LM) and lactose intolerance (LI) for a 4SLHBT that acquired four measurements at 0, 90, 120, and 180 min from the same data set were compared with the results of standard LHBT.nnnRESULTSnSixty IBS-D patients and 60 HVs were studied. The genotype in all participants was C/C-13910. LM and LI detection rates increased with lactose dose from 10 g, 20 g to 40 g in both groups (P < 0.001). 4SLHBT showed excellent diagnostic concordance with standard LHBT (97%-100%, Kappau200bu200b 0.815-0.942) with high sensitivity (90%-100%) and specificity (100%) at all three lactose doses in both groups.nnnCONCLUSIONnReducing the number of measurements from 13 to 4 samples did not significantly impact on the accuracy of LHBT in health and IBS-D. 4SLHBT is a valid test for assessment of LM and LI in clinical practice.

MLCK-mediated intestinal permeability promotes immune activation and visceral hypersensitivity in PI-IBS mice

Alterations in intestinal permeability regulated by tight junctions (TJs) are associated with immune activation and visceral hypersensitivity in irritable bowel syndrome (IBS). Myosin light chain kinase (MLCK) is an important mediator of epithelial TJ. The aim of this study is to investigate the role of MLCK in the pathogenesis of IBS using a post infectious IBS (PI‐IBS) mouse model.