A comparison between lactose breath test and quick test on duodenal biopsies for diagnosing lactase deficiency in patients with self-reported lactose intolerance

Prebiotic Strategies to Manage Lactose Intolerance Symptoms

Lactose intolerance, which affects about 65-75% of the world's population, is caused by a genetic post-weaning deficiency of lactase, the enzyme required to digest the milk sugar lactose, called lactase non-persistence. Symptoms of lactose intolerance include abdominal pain, bloating and diarrhea. Genetic variations, namely lactase persistence, allow some individuals to metabolize lactose effectively post-weaning, a trait thought to be an evolutionary adaptation to dairy consumption. Although lactase non-persistence cannot be altered by diet, prebiotic strategies, including the consumption of galactooligosaccharides (GOSs) and possibly low levels of lactose itself, may shift the microbiome and mitigate symptoms of lactose consumption. This review discusses the etiology of lactose intolerance and the efficacy of prebiotic approaches like GOSs and low-dose lactose in symptom management.

Food Intolerances, Food Allergies and IBS: Lights and Shadows

This narrative review delves into the intricate relationship between irritable bowel syndrome (IBS) and food intolerances. IBS, a chronic functional gastrointestinal disorder, is characterized by symptoms like abdominal pain and altered bowel habits. The prevalence of IBS has increased globally, especially among young adults. Food and dietary habits play a crucial role in IBS management. About 85-90% of IBS patients report symptom exacerbation linked to specific food consumption, highlighting the strong connection between food intolerances and IBS. Food intolerances often exhibit a dose-dependent pattern, posing a challenge in identifying trigger foods. This issue is further complicated by the complex nature of gastrointestinal physiology and varying food compositions. This review discusses various dietary patterns and their impact on IBS, including the low-FODMAP diet, gluten-free diet, and Mediterranean diet. It highlights the importance of a personalized approach in dietary management, considering individual symptom variability and dietary history. In conclusion, this review emphasizes the need for accurate diagnosis and holistic management of IBS, considering the complex interplay between dietary factors and gastrointestinal pathophysiology. It underlines the importance of patient education and adherence to treatment plans, acknowledging the challenges posed by the variability in dietary triggers and the psychological impact of dietary restrictions.

Malignancies in Patients with Celiac Disease: Diagnostic Challenges and Molecular Advances

Celiac disease (CD) is a multiorgan autoimmune disorder of the chronic intestinal disease group characterized by duodenal inflammation in genetically predisposed individuals, precipitated by gluten ingestion. The pathogenesis of celiac disease is now widely studied, overcoming the limits of the purely autoimmune concept and explaining its hereditability. The genomic profiling of this condition has led to the discovery of numerous genes involved in interleukin signaling and immune-related pathways. The spectrum of disease manifestations is not limited to the gastrointestinal tract, and a significant number of studies have considered the possible association between CD and neoplasms. Patients with CD are found to be at increased risk of developing malignancies, with a particular predisposition of certain types of intestinal cancer, lymphomas, and oropharyngeal cancers. This can be partially explained by common cancer hallmarks present in these patients. The study of gut microbiota, microRNAs, and DNA methylation is evolving to find the any possible missing links between CD and cancer incidence in these patients. However, the literature is extremely mixed and, therefore, our understanding of the biological interplay between CD and cancer remains limited, with significant implications in terms of clinical management and screening protocols. In this review article, we seek to provide a comprehensive overview of the genomics, epigenomics, and transcriptomics data on CD and its relation to the most frequent types of neoplasms that may occur in these patients.

Lactase Deficiency Diagnosed by Endoscopic Biopsy-based Method is Associated With Positivity to Glucose Breath Test

Background/Aims

Lactase deficiency, which has many similarities with small intestinal bacterial overgrowth (SIBO), causes various gastrointestinal symptoms. We estimate the prevalence of SIBO in patients with intestinal symptoms from dairy products and investigate the association between lactase deficiency (LD) and SIBO.

Methods

This prospective study included patients with functional intestinal symptoms from dairy product indigestion. A questionnaire on gastrointestinal symptoms, a hydrogen (H₂)-methane glucose breath test (GBT) for SIBO, and lactose intolerance quick test (LQT) for LD using upper gastrointestinal endoscopy were performed.

Results

A total of 88 patients, 29 (33.0%) with severe and 36 (40.9%) with mild LD were included. Sixteen patients (18.2%) were GBT positive. Patients with LQT negativity indicating severe LD showed a higher positivity to GBT or GBT (H₂) than the historic controls (27.6% vs 6.7%, P = 0.032). There was no difference in the items on the symptom questionnaire according to the presence of LD or SIBO, except for higher symptom scores for urgency in GBT-positive patients. There were more LQT-negative patients in the GBT (H₂)-positive group than in the other groups (27.6% vs 10.2%, P = 0.036). Moreover, only GBT (H₂)-positivity was significantly associated with a higher risk of LQT negativity in multivariate analysis (OR, 4.19; P = 0.029).

Conclusions

SIBO producing H₂ is common in patients with severe LD suspected lactose intolerance. SIBO may be a new therapeutic target for managing intestinal symptoms in patients with lactose intolerance.

Relationships of Intestinal Lactase and the Small Intestinal Microbiome with Symptoms of Lactose Intolerance and Intake in Adults

BACKGROUND

Approximately two-thirds of adults are genetically predisposed to decreased lactase activity after weaning, putting them at risk of lactose intolerance. However, symptoms are a poor marker of lactose maldigestion.

AIMS

We assessed association between self-reported lactose intolerance and intestinal lactase, lactose intake, and the small intestinal microbiome.

METHODS

Patients 18-75 years presenting for upper endoscopy were recruited prospectively. Observational study participants completed a lactose intolerance symptom questionnaire and reported lactose intake. Post-bulbar biopsies were obtained to measure lactase activity and assess the small intestinal mucosal microbiome. We compared intestinal lactase between patients with and without lactose intolerance. We assessed associations between lactose intolerance symptoms and lactase and lactose intake. We examined associations of small bowel microbial composition with self-reported lactose intolerance and symptoms.

RESULTS

Among 34 patients, 23 (68%) reported lactose intolerance. Those with lactose intolerance had higher total symptom scores, more frequent bowel urgency, and more bowel movements after consuming dairy. The proportion of individuals with abnormal lactase activity did not differ by lactose intolerance status. Median lactase levels were correlated with total lactose intolerance symptom scores (p = 0.038) and frequency of bowel urgency (p = 0.012). Daily lactose intake did not differ between groups. In 19 patients, we observed significant associations of small intestinal microbiome beta diversity with stool consistency after consuming dairy (p = 0.03).

CONCLUSIONS

Intestinal lactase is associated with lactose intolerance symptoms and bowel urgency in adults but does not distinguish the clinical phenotype entirely. Studying other contributing factors (microbiota, diet) may further clarify the pathophysiology of lactose intolerance.

Prevalence of Lactose Intolerance in Patients with Hashimoto Thyroiditis and Impact on LT4 Replacement Dose

Purpose: to determine lactose intolerance (LI) prevalence in women with Hashimoto’s thyroiditis (HT) and assess the impact of LI on LT4 replacement dose. Methods. consecutive patients with HT underwent Lactose Breath Test and clinical/laboratory data collection. Unrelated gastrointestinal disorders were carefully ruled out. Lactose-free diet and shift to lactose-free LT4 were proposed to patients with LI. Results: we enrolled 58 females (age range, 23−72 years) with diagnosis of HT. In total, 15 patients were euthyroid without treatment, and 43 (74%) euthyroid under LT4 (30 of them with a LT4 formulation containing lactose). Gastrointestinal symptoms were present in 84.5% of patients, with a greater prevalence in change in bowel habits in lactose-intolerant patients (p < 0.0001). The cumulative LT4 dose required did not differ in patients with or without LI. No significant difference in both TSH values and LT4 dose were observed in patients shifted to lactose-free LT4 and diet at 3 and 6 months compared to baseline. Conclusion: the prevalence of LI in patients with HT was 58.6%, not different from global prevalence of LI. In the absence of other gastrointestinal disorders, LI seems not to be a major cause of LT4 malabsorption and does not affect the LT4 required dose in HT patients.

Validation of a modified cow's milk-related symptom score (CoMISS) for screening of lactose intolerance in adults

INTRODUCTION

Lactose intolerance (LI) is the failure to digest foods and beverages containing the lactose present in milk. LI can present by many digestive symptoms.

OBJECTIVE

To validate the modified CoMiSS score for prediction of LI, that was confirmed by a stool acidity test.

PATIENTS AND METHODS

A cross-sectional study, was conducted at Ain Shams University Hospitals/Gastrointestinal Clinics, and included one hundred adult participants during the period from December 2018 to December 2019. Enrolled patients had one or more gastrointestinal symptoms and were subjected to a stool acidity test (fecal PH test) as a reference test and modified CoMiSS as an index test.

RESULTS

The mean age of participants was 35.30 ± 10.714 years old; 55% were females, and their mean body mass index (BMI) was 23.08 ± 2.080 kg/m², with no significant relation between LI and patients` gender or BMI. Out of the studied participants 24% had positive stool PH, LI diagnosed according to modified CoMISS was present among 19% of them. The mean value of modified CoMISS Score was significantly higher in positive cases (12.37) compared to negative LI participants (2.33) as p < .001. Area under ROC Curve was 0.998, at the selected cut-off value 8, the sensitivity was 89.5% and specificity was 100% thus, levels of questionnaire scoring of 8 or higher would indicate presence of lactose intolerance.

CONCLUSION

Modified CoMiSS is a simple, fast, and easy-to-use tool that can predict LI, with a cut-off value of >8, the Area under the ROC Curve was 0.998, sensitivity 89.5%, and specificity was 100%.

Can Lactose Intolerance Be a Cause of Constipation? A Narrative Review

Lactose intolerance and constipation are common in children and impact everyday life, not only for patients but also their families. Both conditions can be comorbid with other diseases or form a part of their clinical presentation, but constipation is not usually associated with lactose intolerance. The typical symptoms of lactose intolerance include abdominal pain, bloating, flatus, diarrhoea, borborygmi, and less frequently nausea and vomiting. In approximately 30% of cases, constipation can be a symptom of lactose intolerance. Constipation is characterized by infrequent bowel movements, hard and/or large stools, painful defecation, and faecal incontinence, and is often accompanied by abdominal pain. This paper provides a narrative review on lactose intolerance, its epidemiology, pathogenesis, the correlation between lactose intolerance and constipation in children, and potential mechanisms of such association.

Development of Personalized Nutrition: Applications in Lactose Intolerance Diagnosis and Management

Recent discoveries in the “omics” field and the growing focus on preventive health have opened new avenues for personalized nutrition (PN), which is becoming an important theme in the strategic plans of organizations that are active in healthcare, food, and nutrition research. PN holds great potential for individual health optimization, disease management, public health interventions, and product innovation. However, there are still multiple challenges to overcome before PN can be truly embraced by the public and healthcare stakeholders. The diagnosis and management of lactose intolerance (LI), a common condition with a strong inter-individual component, is explored as an interesting example for the potential role of these technologies and the challenges of PN. From the development of genetic and metabolomic LI diagnostic tests that can be carried out in the home, to advances in the understanding of LI pathology and individualized treatment optimization, PN in LI care has shown substantial progress. However, there are still many research gaps to address, including the understanding of epigenetic regulation of lactase expression and how lactose is metabolized by the gut microbiota, in order to achieve better LI detection and effective therapeutic interventions to reverse the potential health consequences of LI.

Lactose Intolerance and Its Dietary Management: An Update

Milk is the most common food consumed worldwide and is also a major ingredient in the preparation of various dairy products. However, despite the high production and consumption of milk and milk-based products, there is a large percent of the world's population that suffer from allergies to milk solids and lactose intolerance. Lactose intolerance specifically means the inability of the body to breakdown the sugar to its simplest form for assimilation and it is due to the inefficiency or lack of the enzyme in the human body. The most convenient prevention method for the affected population is to avoid milk and milk-based products but this may be a cause of development of other health related issues that result from inadequate nutrient consumption. To help find an alternative to this problem, this study aims at first studying the underlying information on lactose intolerance and then studying plant-based beverages as a possible alternative to milk and milk-based products. Key teaching pointsLactose intolerance specifically means the inability of the body to breakdown the sugar to its simplest form for assimilation and it is due to the inefficiency or lack of the enzyme in the human body.Consumption of probiotics may help relieve the symptoms of lactose intolerance.Soy beverage can be an economical alternative for lactose intolerant populations and has calcium content comparable to bovine milk.Calcium absorption in fortified plant based beverages depends upon type of calcium salt used.

Human Health Effects of Lactose Consumption as a Food and Drug Ingredient

Lactose is a reducing sugar consisting of galactose and glucose, linked by a β (1→4) glycosidic bond, considered as an antioxidant due to its α-hydroxycarbonyl group. Lactose is widely ingested through the milk and other unfermented dairy products and is considered to be one of the primary foods. On the other hand, lactose is also considered as one of the most widely used excipients for the development of pharmaceutical formulations. In this sense, lactose has been related to numerous drug-excipient or drug-food pharmacokinetic interactions. Intolerance, maldigestion and malabsorption of carbohydrates are common disorders in clinical practice, with lactose-intolerance being the most frequently diagnosed, afflicting 10% of the world's population. Four clinical subtypes of lactose intolerance may be distinguished, namely lactase deficiency in premature infants, congenital lactase deficiency, adult-type hypolactasia and secondary lactase intolerance. An overview of the main uses of lactose in human nutrition and in the pharmaceutical industry and the problems derived from this circumstance are described in this review.

Association between Inflammatory Bowel Disease and Lactose Intolerance: Fact or Fiction

Background/Aims

Inflammatory bowel disease (IBD) is a complex condition precipitated by genetic susceptibility and possibly a disturbed microbiome. The role of dairy foods in IBD is controversial. This study examined the association between lactose intolerance (LI) and IBD.

Methods

Data on hospital admissions of all IBD adult patients were extracted from the National Inpatient Sample database between 2004 and 2014. The comorbidities and outcomes of interest were defined by querying all the diagnostic and procedural fields for the corresponding International Classification of Diseases 9th version (ICD-9) codes. Patients with IBD were defined as the "study group," and the patients who did not have IBD were defined as the "control group". LI was identified in both groups using the ICD-9 codes. Multivariate logistic regression was performed to examine the association between IBD and LI.

Results

The total population was 71,342,237 patients, of which 598,129 (0.83%) had IBD. The IBD patients were younger (52 years vs. 57 years) and with fewer females (57.5% vs. 60.1%) (p<0.001 for all). After adjusting for the potential confounding factors, the IBD group had a significantly higher rate of LI (OR 2.71, 95% CI 2.55-2.88, p<0.001) compared to the non-IBD group. The findings were similar on the further stratification of IBD into Crohn's disease compared to the control group (OR 2.70, 95% CI 2.50-2.92, p<0.001) and ulcerative colitis compared to the control group (OR 2.71, 95% CI 2.46-2.98, p<0.001).

Conclusions

IBD patients have a 2.7 times higher risk of LI. Screening for LI in this population is warranted to avoid confusing or overlapping symptomatology.

Congruency of Genetic Predisposition to Lactase Persistence and Lactose Breath Test

The physiological decline of lactase production in adulthood, in some individuals, is responsible for the so-called “Lactose Intolerance.” This clinical syndrome presents with gastrointestinal and non-gastrointestinal symptoms following the consumption of dairy containing food. Lactose intolerance can be evaluated by means of the Lactose Breath Test (phenotype) and/or genetic evaluation of lactase-gene polymorphism (genotype). A comparison of the two tests was carried out in a large number of symptomatic adult subjects, which are selected and not representative of the general population. Congruency was as high as 88.6%. Among lactase non-persistent (genotype C/C), 14 subjects showed a negative Lactose Breath Test (LBT), possibly due to young age. Among lactase-persistent (genotype C/T), four subjects showed a positive LBT, which helps to diagnose secondary lactose intolerance. Symptoms, both gastrointestinal and extra-gastrointestinal, were reported by 90% of patients during the breath test. Clinical use of both tests in the same patients could be taken into consideration as a sharp diagnostic tool. We suggest considering the use of the genetic test after LBT administration, when secondary hypolactasia is suspected, for completion of diagnostic procedures.

Lactose Intolerance, Dairy Avoidance, and Treatment Options

Lactose intolerance refers to symptoms related to the consumption of lactose-containing dairy foods, which are the most common source for this disaccharide. While four causes are described, the most common is the genetically-determined adult onset lactose maldigestion due to loss of intestinal lactase governed by control of the gene by a 14,000 kb promoter region on chromosome 2. Gastrointestinal symptoms from lactose have expanded to include systemic effects and have also been confounded by other food intolerances or functional gastrointestinal disorders. Partly because lactose maldigestion is often interpreted as lactose intolerance (symptoms), focus of therapy for these symptoms starts with lactose restriction. However, withholding of dairy foods completely is not appropriate due to a more favorable impact on health. Industrial efforts to substitute with plant-based products is not completely successful at this time. This narrative article reviews the complexities of the perception of lactose intolerance, its epidemiology, and pathogenesis. Treatments are discussed, including the inappropriateness of dairy avoidance. In conjunction, effects of dairy products on 19 common diseases are reviewed. Different methods of treatment, lactose-reduced products, plant-based dairy substitutes, adaptation, prebiotics, exogenous lactase, probiotics, and some other dietary interventions are further discussed.

Lactose Maldigestion, Malabsorption, and Intolerance: A Comprehensive Review with a Focus on Current Management and Future Perspectives

Milk is a fundamental component of the diet of every mammal; nevertheless, not every individual can tolerate this kind of food, especially in adulthood. However, lactose intolerance has only been recognized in the last 50 years, and currently, lactose intolerance is defined as a clinical syndrome characterized by pain, abdominal distention, flatulence, and diarrhoea that occur after lactose consumption. Lactose is currently a common disaccharide in human nutrition, both in breastfed infants and in adults, but its digestion requires a specialized enzyme called lactase. The genetically programmed reduction in lactase activity during adulthood affects most of the world’s adult population and can cause troublesome digestive symptoms, which may also vary depending on the amount of residual lactase activity; the small bowel transit time; and, especially, the amount of ingested lactose. Several diagnostic tests are currently available for lactose intolerance, but the diagnosis remains challenging. The treatment for lactose intolerance mainly consists of reducing or eliminating the dietetic amount of lactose until the symptoms disappear, but this is hard to achieve, as lactose is present in dairy products and is even commonly used as a food additive. In addition to dietetic restriction of lactose-containing foods, lactase can be administered as an enzymatic food supplement, but its efficacy is still controversial. Recently, probiotics have been proposed for the management of lactose intolerance; certain probiotic strains have shown specific β-galactosidase activity, thus aiding in the digestion of lactose. The aim of this paper was to review the current knowledge about lactose intolerance and to discuss the potential for the use of specific probiotic strains such as dietary supplements in lactose-intolerant patients.

Retrospective analysis of a lactose breath test in a gastrointestinal symptomatic population of Northeast Italy: use of (H2+2CH4) versus H2 threshold

Background

Lactose malabsorption is normally evaluated by measuring exhaled H₂ produced by intestinal flora, from unabsorbed lactose. However, differing microbiome composition can lead to the production of CH₄ instead of H₂; hence, some authors challenge the H₂ method sensitivity and favor the evaluation of both intestinal gases.

Aim

To compare different approaches to usage of a lactose breath test for lactose malabsorption diagnosis, after medical evaluation of gastrointestinal symptoms.

Methods

In a retrospective observational study, we compared the 2 approaches in a population of 282 subjects in Northern Italy. Following oral lactose administration, exhaled samples were harvested every 30 minutes for 4 hours and prepared for H₂ and CH₄ analysis. Basal gas levels were subtracted from H₂ and CH₄ ppm and values at 4 hours and peaks were considered for analysis.

Results

Applying the standard methodology, which takes separately into consideration H₂ and CH₄ produced in the intestinal lumen, the results indicated that 11.7% of the patients were diagnosed “positive” for hypolactasia, differently from what was expected. Conversely, taking into consideration the sum of H₂ and CH₄, the percentage increased to 62.8%, closer to the expected one. No significant differences were found when comparing the 2 groups for age, gender, or symptoms. The sizable difference between the 2 approaches is likely linked to gut microbiome variability, and consequently the different production of the 2 gases, in the population.

Conclusion

The threshold normally used for lactose breath test should be reconsidered and changed, merging H₂ and CH₄ stoichiometric values to increase sensitivity.

Concordance between Lactose Quick Test, hydrogen-methane breath test and genotyping for the diagnosis of lactose malabsorption in children

BACKGROUND

Lactose intolerance is a frequent condition in certain populations. Different methods for diagnosis exist. There is scarce literature regarding Lactose Quick Test (LQT) and concordance with other methods for lactose intolerance diagnosis in children.

METHODS

Prospectively, we included children who underwent gastroduodenoscopy for evaluation of abdominal pain. We obtained a duodenal sample for LQT and blood sample for genetic test to evaluate LCT C>T_-13910 variant. Later, patients underwent breath test with lactose, to evaluate malabsorption. We evaluated the concordance between the three different tests.

KEY RESULTS

We included 46 patients, 56.5% women. Mean age was 13.2 years (range 9-18 years). 66.6% of patients had lactose malabsorption according to breath test; 64.4% were homozygous CC; and 91.3% had hypolactasia (mild or severe) according to LQT. None of the patients with normolactasia had altered breath test. Genetic test had a substantial agreement (k = 0.675) with breath test and fair agreement (k = 0.301) with LQT. LQT had fair agreement (k = 0.348) with breath test.

CONCLUSIONS & INFERENCES

Genetic test had better concordance with breath test than LQT to diagnose lactose malabsorption, however, none of the patients with normal LQT had lactose malabsorption. In patients who undergo gastroduodenoscopy to study abdominal pain, it seems reasonable to perform LQT, and, in those with hypolactasia, to perform breath test.

Lactose malabsorption in systemic sclerosis

BACKGROUND

There are no studies on systemic sclerosis (SSc) assessing the relationship between food intake, especially lactose, and gastrointestinal dysfunction.

AIM

To determine the prevalence of lactose malabsorption, using lactose breath test, in patients with SSc. To evaluate the correlation between lactose malabsorption and gastrointestinal involvement. To predict which SSc patients exhibit lactose malabsorption.

METHODS

Seventy-seven consecutive Caucasian patients with SSc and 20 control subjects underwent lactose breath test. All patients also completed a questionnaire on digestive symptoms, and a global symptom score (GSS) was calculated.

RESULTS

The prevalence of lactose malabsorption was higher in SSc patients than in controls (44.3% vs. 10%; P = 0.004). We observed a marked correlation between the presence of lactose malabsorption and: higher values of GSS (P < 0.0001); severe oesophageal (P = 0.018) and small intestinal (P = 0.04) motor disorders; and joint involvement (P = 0.019). Furthermore, in SSc patients with symptomatic lactose malabsorption, the median value of GSS of digestive symptoms was lower after initiation of lactose-free diet (P < 0.0001).

CONCLUSIONS

Our study underscores the fact that lactose malabsorption often occurs in patients with systemic sclerosis. Furthermore, our findings highlight the fact that lactose breath test is a helpful, noninvasive method, by identifying the group of patients with systemic sclerosis with symptomatic lactose malabsorption that may benefit from a reduction in lactose intake.

Assessment of intestinal malabsorption

Significant efforts have been made in the last decade to either standardize the available tests for intestinal malabsorption or to develop new, more simple and reliable techniques. The quest is still on and, unfortunately, clinical practice has not dramatically changed. The investigation of intestinal malabsorption is directed by the patient's history and baseline tests. Endoscopy and small bowel biopsies play a major role although non-invasive tests are favored and often performed early on the diagnostic algorithm, especially in paediatric and fragile elderly patients. The current clinically available methods and research tools are summarized in this review article.

Clinical evaluation, biochemistry and genetic polymorphism analysis for the diagnosis of lactose intolerance in a population from northeastern Brazil

OBJECTIVE

This work aimed to evaluate and correlate symptoms, biochemical blood test results and single nucleotide polymorphisms for lactose intolerance diagnosis.

METHOD

A cross-sectional study was conducted in Fortaleza, Ceará, Brazil, with a total of 119 patients, 54 of whom were lactose intolerant. Clinical evaluation and biochemical blood tests were conducted after lactose ingestion and blood samples were collected for genotyping evaluation. In particular, the single nucleotide polymorphisms C>T-13910 and G>A-22018 were analyzed by restriction fragment length polymorphism/polymerase chain reaction and validated by DNA sequencing.

RESULTS

Lactose-intolerant patients presented with more symptoms of flatulence (81.4%), bloating (68.5%), borborygmus (59.3%) and diarrhea (46.3%) compared with non-lactose-intolerant patients (p<0.05). We observed a significant association between the presence of the alleles T-13910 and A-22018 and the lactose-tolerant phenotype (p<0.05). After evaluation of the biochemical blood test results for lactose, we found that the most effective cutoff for glucose levels obtained for lactose malabsorbers was <15 mg/dL, presenting an area under the receiver operating characteristic curve greater than 80.3%, with satisfactory values for sensitivity and specificity.

CONCLUSIONS

These data corroborate the association of these single nucleotide polymorphisms (C>T-13910 and G>A-22018) with lactose tolerance in this population and suggest clinical management for patients with lactose intolerance that considers single nucleotide polymorphism detection and a change in the biochemical blood test cutoff from <25 mg/dL to <15 mg/dL.

Adult lactose digestion status and effects on disease

BACKGROUND

Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes.

OBJECTIVES

To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions.

METHODS

A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic.

RESULTS

The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide.

DISCUSSION

The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases.

CONCLUSIONS

Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing.

Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment

Lactose malabsorption is a common condition caused by reduced expression or activity of lactase in the small intestine. In such patients, lactose intolerance is characterized by abdominal symptoms (e.g. nausea, bloating, and pain) after ingestion of dairy products. The genetic basis of lactose malabsorption is established and several tests for this condition are available, including genetic, endoscopic, and H2-breath tests. In contrast, lactose intolerance is less well understood. Recent studies show that the risk of symptoms after lactose ingestion depends on the dose of lactose, lactase expression, intestinal flora, and sensitivity of the gastrointestinal tract. Lactose intolerance has recently been defined as symptoms developing after ingestion of lactose which do not develop after placebo challenge in a person with lactose maldigestion. Such blinded testing might be especially important in those with functional gastrointestinal diseases in whom self-reported lactose intolerance is common. However, placebo-controlled testing is not part of current clinical practice. Updated protocols and high-quality outcome studies are needed. Treatment options of lactose intolerance include lactose-reduced diet and enzyme replacement. Documenting the response to multiple doses can guide rational dietary management; however, the clinical utility of this strategy has not been tested. This review summarizes the genetic basis, diagnosis, and treatment of lactose malabsorption and intolerance.