Extragastrointestinal Symptoms and Sensory Responses During Breath Tests Distinguish Patients With Functional Gastrointestinal Disorders.

INTRODUCTION: Patients with functional gastrointestinal disorders (FGIDs) are classified based on their gastrointestinal (GI) symptoms, without considering their frequent extra-GI symptoms. This study defined subgroups of patients using both GI and extra-GI symptoms and examined underlying mechanisms with fructose and lactose breath tests. METHODS: Latent class analysis defined distinct clusters of patients with FGID based on their long-term GI and extra-GI symptoms. Sensory and breath gas responses after fructose and lactose ingestion were compared across symptom clusters to investigate differences in sensory function and fermentation by intestinal microbiota. RESULTS: Six symptom clusters were identified in 2,083 patients with FGID. Clusters were characterized mainly by GI fermentation-type (cluster 1), allergy-like (cluster 2), intense pain-accentuated GI symptoms (cluster 3), central nervous system (cluster 4), musculoskeletal (cluster 5), and generalized extra-GI (cluster 6) symptoms. In the 68% of patients with complete breath tests, the areas under the curve of GI and central nervous system symptoms after fructose and lactose ingestion differed across the clusters (P < 0.001). The clusters with extensive long-term extra-GI symptoms had greater symptoms after the sugars and were predominantly women, with family or childhood allergy histories. Importantly, the areas under the curves of hydrogen and methane breath concentrations were similar (P > 0.05) across all symptom clusters. Rome III criteria did not distinguish between the symptom clusters. DISCUSSION: Patients with FGID fall into clusters defined extensively by extra-GI symptoms. Greater extra-GI symptoms are associated with evidence of generalized sensory hypersensitivity to sugar ingestion, unrelated to intestinal gas production. Possible underlying mechanisms include metabolites originating from the intestinal microbiota and somatization.

Assessment of tryptophan metabolism and signs of depression in individuals with carbohydrate malabsorption.

This prospective cross-sectional study aimed to investigate the potential association between primary-adult lactose malabsorption, fructose malabsorption, tryptophan (TRP) metabolism and the presence of depressive signs. Overall 251 patients, who were referred for lactase gene C/T-13910 polymorphism genotyping and fructose hydrogen/methane breath testing, were included. All participants filled out the Beck Depression Inventory (BDI II). Serum concentrations of tryptophan (TRP), kynurenine (KYN), kynuric acid (KYNA), and TRP competing amino acids (leucine, isoleucine, valine, phenylalanine, tyrosine) were measured by high-pressure liquid-chromatography. Logistic regression analysis was performed with lactose malabsorption, fructose malabsorption and all potential biomarkers of TRP metabolism to assess the effect on signs of depression, defined as a BDI II score > 13. Primary-adult lactose malabsorption and fructose malabsorption was detected in 65 (25.90%) and 65 (25.90%) patients, respectively. Fructose malabsorption was significantly associated with BDI II score, whereas no such relationship was found for lactose malabsorption. Serum levels of TRP and TRP metabolites were no predictors of depression. The authors suggest to conduct further prospective longitudinal studies in order to get further insight of associations between carbohydrate malabsorption, biomarkers and mood disorders.

Perception of lactose intolerance impairs health-related quality of life.

BACKGROUND/OBJECTIVES: Chronic conditions impair perception of well-being. Malabsorption of lactose is the most frequent form of malabsorption and manifests as lactose intolerance. There is a lack of information regarding their impact on self-perception of health. The objective of this study is to determine the subjective impact of self-reported lactose intolerance or objective lactose malabsorption on patient health by using a patient-reported outcome to measure health-related quality of life (HRQOL) and modification of lactose-containing food diet. SUBJECTS/METHODS: A 3-year prospective, cross-sectional study was performed in patients referred for a lactose hydrogen breath test. Patients were asked about their subjective opinion relative to their lactose tolerance and completed a validated, specific questionnaire to determine symptoms of intolerance during habitual consumption of dairy. A 50-g lactose breath test was then performed. Patients were grouped as absorbers vs malabsorbers and tolerant vs intolerants. RESULTS: A total of 580 patients were included (median age 30 years, 419 female). Overall, 324 patients (56%) considered themselves lactose intolerant and that perception was associated with avoidance of dairy consumption (55% vs only 9% of self-defined tolerants). Self-perception of intolerance was associated with lower HRQOL scores (median, 60 vs 70, P<0.01). In contrast, lactose objective malabsorption was not clearly associated with dairy avoidance (41% of malabsorbers avoided dairy vs 31% of absorbers). However, HRQOL scores were also significantly lower in malabsorbers than in absorbers (60 vs 70 respectively, P<0.001). CONCLUSIONS: Subjective perception of lactose intolerance affects the decision to avoid dairy even more than objective malabsorption. However, both self-perception of lactose intolerance and objective lactose malabsorption are associated with poorer perceived quality of life.

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

BACKGROUND: 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. METHODS: Consecutive patients completed questionnaires to assess digestive health (Rome III), psychological state (HADS), life event stress (LES), food intake, and quality-of-life (SF-8). A representative sample completed genetic studies and hydrogen breath testing (HBT) at the clinically relevant dose of 20 g lactose. KEY RESULTS: SLI was present in 411/910 (45%) clinic patients with functional abdominal symptoms. The genotype in all subjects was C/C-13910. A small number of novel SNPs in lactase promoter region were identified, including C/T-13908 which appeared to confer lactase persistence. Over half of the patients (54%) completed the 20 g lactose HBT with 58% (285/492) reporting typical symptoms. Positive and negative predictive values of SLI for abdominal symptoms during HBT were 60% and 44%, respectively. Psychological state and stress were not associated with SLI in clinic patients. SLI impacted on physical quality-of-life and was associated with reduced ingestion of dairy products, legumes, and dried fruit (p ≤ 0.05). CONCLUSIONS & INFERENCES: In a lactase deficient population, approximately half of patients attending clinic with functional gastrointestinal symptoms reported intolerance to dairy products; however, SLI did not predict findings on 20 g lactose HBT. Independent of psychosocial factors, SLI impacted on quality-of-life and impacted on food choices with restrictions not limited to dairy products.

Perception of lactose intolerance in irritable bowel syndrome patients.

INTRODUCTION: The importance of lactose malabsorption in irritable bowel syndrome (IBS) is not well defined and these patients often complain of lactose intolerance. To objectively measure lactose malabsorption, a hydrogen breath test (HBT) can be performed, but a discrepancy emerges between the results of the HBT and the symptomatic response during the HBT. AIMS: To determine in a group of IBS patients whether self-perceived lactose intolerance and the symptomatic response to lactose HBT were conditioned by other factors besides the presence of lactose malabsorption. MATERIALS AND METHODS: Oral challenge to lactose (50 g) was tested in 51 IBS patients to assess HBT malabsorption and the symptomatic response to lactose intolerance was scored on a validated questionnaire. Allergological screening for common inhalants and food allergens (including cow's milk) was performed. The presence of psychological factors (e.g. anxiety, depression, fatigue) was evaluated using validated questionnaires. RESULTS: A total of 21 out of 51 patients (41.1%) were self-perceived to be lactose intolerant, 24/51 (47%) had a positive HBT, and 14/51 (27.4%) presented with symptoms of lactose intolerance during HBT. The serological screening for inhalant and food allergens was positive in 6/21 (28.6%) and 4/21 (19%) of patients who self-perceived lactose intolerance and in 5/14 (37.5%) and 3/14 (21.4%) in intolerant patients symptomatic during HBT. Only 1/51 (1.9%) presented evidence of IgE-mediated hypersensitivity to cow's milk. Patients who experienced symptoms of lactose intolerance during HBT presented more severe IBS symptoms [326 (296-398) vs. 215 (126-295) P=0.05] and a higher score of anxiety, depression, and fatigue. Factors influencing the symptoms of lactose intolerance during HBT resulted in an increase in hydrogen produced and in the severity of IBS. CONCLUSION: In a cohort of 51 IBS patients, the symptoms of lactose intolerance during HBT were influenced by the capacity to absorb lactose and the severity of IBS. Other factors, such as the psychological status or an adverse reaction to milk, merit consideration as potential cofactors involved in lactose perception and tolerance.

Perceptions of caregivers of patients with cow's milk allergy regarding the treatment / Percepção dos familiares de pacientes com alergia ao leite de vaca em relação ao tratamento

The aim of this qualitative study was to understand the perceptions of caregivers of children and adolescents with cow's milk allergy regarding the disease and its treatment. Nine caregivers were interviewed and content analysis method was used. Three categories with subcategories emerged: treatment and education of the patient and their caregivers (life experiences, bases of treatment, coping with the disease), resolution of the disease (hope, gradual improvement), quality of life (social inclusion, family daily activities, costs of dietary treatment). Caregivers experienced difficulties during the initial treatment but pointed out that the guidance given during follow-up made the adjustments easier. Family members commented on the difficulties about lack of cooperation from other family members regarding the restrictive diet, their experience coping with the allergic reaction, doubts about the treatment and gaps on knowledge about the disease by other physicians and people. Some of them believed that there is no treatment for the disease, because there are no drugs or vaccines, but they were waiting for cure. The majority of relatives were satisfied with the gradual improvement of patients observed by reduction on the severity of symptoms and tolerance of milk traces within foods. In addition, they commented on the efforts to give a normal life for their children, the changes in their daily lives and the difficulty to buy special products. Concluding, caregivers of children and adolescents with cow's milk allergy feel a great burden of the disease.(AU)

Este estudo qualitativo teve como objetivo compreender as percepções de familiares de crianças e adolescentes com alergia à proteína do leite de vaca (APLV) em relação à doença e seu tratamento. Foram realizadas nove entrevistas e foi utilizado o método de análise de conteúdo. Surgiram três categorias com subcategorias: tratamento e educação do paciente e familiares (experiências vividas, base do tratamento e como lidar com a doença), resolução da doença (expectativa e melhora gradativa), qualidade de vida (inclusão social, cotidiano familiar e custo dos alimentos). Os familiares vivenciaram dificuldades durante o início do tratamento, mas revelaram que as orientações fornecidas no seguimento tornaram as adaptações à doença mais fáceis. Comentaram sobre as dificuldades em obter a colaboração de outros membros da família em relação à dieta de exclusão, suas experiências frente a uma reação alérgica, dúvidas quanto ao tratamento e lacunas do conhecimento sobre a doença entre outros médicos e na população em geral. Alguns deles acreditavam que não havia tratamento para a APLV, porque não existiam medicamentos ou vacinas, mas mantinham a esperança da descoberta de uma cura. A maioria dos familiares estava satisfeita com a melhora gradativa dos seus filhos, percebida pela redução da gravidade dos sintomas e tolerância a traços de leite. Também comentaram sobre os esforços em proporcionar uma vida normal para seus filhos, as mudanças em suas vidas e a dificuldade em comprar alimentos especiais. Em conclusão, os familiares de crianças e adolescentes com APLV sentem grande impacto da doença.(AU)

Is the subjective perception of lactose intolerance influenced by the psychological profile?

BACKGROUND: Symptoms of lactose intolerance are often attributed to lactose malabsorption but, as this relationship has not been demonstrated when a small dose of lactose similar to that contained in one cup of milk is ingested by intolerant patients, psychological factors may play a role in altered symptom perception. AIM: To assess the hypothesis that the psychological profile influences the symptoms of lactose intolerance. METHODS: One hundred and two consecutive patients underwent a 15 g lactose hydrogen breath test to assess lactose malabsorption. The patients recorded the presence and severity of symptoms of lactose intolerance during the breath test using visual analogue scales. The psychological profile was assessed using a psychological symptom checklist, and health-related quality of life by means of the short-form health survey. RESULTS: Lactose malabsorption and intolerance were diagnosed in, respectively, 18% and 29% of the patients. The two conditions were not associated, and the severity of intolerance was even less in the patients with malabsorption. Multivariate logistic analysis showed that a high somatisation t-score was significantly associated with lactose intolerance (odds ratio 4.184; 1.704-10.309); the effects of the other psychological variables and of lactose malabsorption were not statistically significant. Health-related quality of life was significantly reduced in the patients with somatisation, but not in those with lactose malabsorption. CONCLUSIONS: The symptoms of lactose intolerance during hydrogen breath testing at a low physiological lactose load, are unrelated to lactose malabsorption, but may reveal a tendency towards somatisation that could impair the quality of life.

Lactose malabsorption and intolerance: a systematic review on the diagnostic value of gastrointestinal symptoms and self-reported milk intolerance.

BACKGROUND: When lactose malabsorption gives rise to symptoms, the result is called 'lactose intolerance'. Although lactose intolerance is often bothersome for patients, once recognized it may be managed by simple dietary adjustments. However, diagnosing lactose intolerance is not straightforward, especially in primary care. AIM: To summarize available evidence on the diagnostic performance of gastrointestinal symptoms and self-reported milk (lactose) intolerance in primary care, and the relationship between lactose malabsorption and intolerance. DATA SOURCES: PubMed, EMBASE and reference screening. STUDY SELECTION: Studies were selected if the design was a primary diagnostic study; the patients were adults consulting because of non-acute abdominal symptoms; the diagnostic test included gastrointestinal symptoms and/or self-reported milk intolerance. A total of 26 primary diagnostic studies were included in the review. DATA EXTRACTION: Quality assessment and data extraction were performed by two reviewers independently. They adhered to the most recent guidelines for conducting a diagnostic review as described in the Cochrane Diagnostic Reviewers' Handbook. RESULTS: The diagnostic performance of diarrhea, abdominal pain, bloating, flatulence and self-reported milk intolerance was highly variable. A non-Caucasian ethnic origin was associated with the presence of lactose malabsorption. Both lactose malabsorbers and lactose absorbers reported symptoms during the lactose hydrogen breath test. CONCLUSION: Our review shows that high-quality studies on the diagnosis of lactose malabsorption and intolerance in primary care are urgently needed. An important prerequisite would be to clearly define the concept of lactose intolerance, as well as how it should be assessed.

Subjective perception of lactose intolerance does not always indicate lactose malabsorption.

BACKGROUND & AIMS: Symptomatic lactose intolerance is common; however, abdominal symptoms that patients experience after ingestion of lactose-containing foods can have causes beyond lactose malabsorption. We aimed to determine whether symptoms that patients usually attribute to lactose intolerance are comparable to symptoms provoked by a controlled lactose challenge and whether these symptoms are related to lactose absorption capacity. METHODS: We performed an observational, prospective, transverse study of 353 patients referred for a lactose hydrogen breath test (HBT). Patients completed a validated questionnaire about symptoms associated with consumption of dairy products at home (home symptoms). After a 50-g lactose breath test, they completed the same questionnaire again (lactose challenge symptoms). Patients were assigned to groups of absorbers or malabsorbers according to HBT results and tolerants or intolerants according to the results of the questionnaire. RESULTS: The total symptom score was significantly higher for home symptoms than for the lactose challenge (16 vs 8, P < .01). Symptoms perceived at home were reported to be more intense than those that followed the lactose challenge for lactose absorbers compared with malabsorbers (16 vs 4, P < .01) and lactose tolerants compared with intolerants (12 vs 2, P < .05). Overperception of lactose intolerance at home was similar in men and women. CONCLUSIONS: Daily life symptoms that patients associate with lactose intolerance are often unrelated to lactose malabsorption. Even among true lactose malabsorbers, symptom recall tends to be amplified by the patient. Thus, conventional anamnesis is a highly unreliable tool to establish symptomatic lactose malabsorption.

Impact of molecularly defined hypolactasia, self-perceived milk intolerance and milk consumption on bone mineral density in a population sample in Northern Europe.

OBJECTIVE: Milk intake as a source of calcium is considered an important factor for bone mineral metabolism. Low lactase activity in adult-type hypolactasia (HL) and self-perceived lactose intolerance (LI) are the main limiting factors of milk intake. The aim of this study was to examine the relationship of HL, LI, individual milk consumption and bone mineral density in a population with high milk consumption and a prevalent vitamin D deficiency. MATERIAL AND METHODS: A population-based study of 367 men and women aged 25-70 years was conducted in Estonia. HL was diagnosed by direct sequencing of the LCT gene, bone mineral density and body composition measured by dual energy X-ray absorptiometry (DXA). An original health questionnaire was used to collect data on milk and dairy consumption, self-perceived milk intolerance, supplement usage and fracture history. RESULTS: Lactase genotype and phenotype had no effect on bone mineral density in this high milk consumption population with a prevalent vitamin D insufficiency. Milk consumption was a significant determinant of bone mineral density in Estonia. Self-perceived milk intolerance leads to self-imposed reductions in milk consumption, increases in bone turnover and an increased risk of fracture. CONCLUSIONS: Self-perceived milk-intolerance rather than HL influences milk consumption and has deleterious effects on bone metabolism.

Survey on parenting practices among Chinese in Singapore.

INTRODUCTION: Cultural, religious and personal factors impact greatly on parenting. This survey aims to identify gaps in knowledge and perception about common parenting issues, with respect to mandarin-speaking Chinese in Singapore. There is an emphasis on first-time parents, who the authors feel may be the group which will require additional education and support on these issues. METHODS: A 37-item written survey was conducted before a public mandarin-language forum. Our response rate was 67 percent. RESULTS: Only 44 percent felt that paediatricians allocated sufficient time to discuss parenting issues. 99 percent of parents believed that breast milk was better than formula milk and that 93 percent intended to breastfeed. However, the vast majority of respondents thought that breastfeeding should be stopped if jaundice developed, and that sunning was effective in preventing jaundice. Moreover, the majority did not recognise the seriousness of jaundice, prolonged or otherwise. Widespread misconceptions existed about milk formulas, with half of the respondents thinking that it was necessary to change to lactose-free formula once a child developed diarrhoea. The majority also thought that certain milk formulas could help improve IQ. CONCLUSION: We hope that more comprehensive and accessible parental education will be available to aid in raising awareness of parental practices, and to dispel misconceptions regarding neonatal care.

Self-reported milk intolerance in irritable bowel syndrome: what should we believe?

BACKGROUND & AIMS: The real importance of lactose malabsorption in irritable bowel syndrome (IBS) is still controversial. The aim is to define the relationship between patient perception of milk tolerance/intolerance, lactose malabsorption and abdominal symptoms in IBS. METHODS: A hydrogen breath test (HBT) after an oral load of lactose was carried out in 475 consecutive IBS patients, diagnosed according to the Rome criteria. Data were analyzed in 201 age- and sex-matched pairs of IBS patients, classified according to self-reported milk tolerance/intolerance. Hydrogen peak and excretion, predominant presenting symptom and the occurrence of symptoms during the test, were evaluated. RESULTS: The prevalence of positive HBT and the occurrence of symptoms during the test was similar in milk "tolerant" (68.6%, 40.7% respectively) and "intolerant" patients (75.6%, 42.7% respectively), as well as peak (76.4 vs 75.2 ppm) and amount of H2 excreted (57.8 vs. 53.2 ppm/h). The positive predictive value for self-reported milk intolerance was 0.75, and the negative predictive value in regular milk users was 0.31, reflecting the prevalence of lactose malabsorption in the general population more than the awareness of milk tolerance. CONCLUSIONS: In IBS patients, self-reported milk intolerance does not help in identifying lactose malabsorbers. The opposite does not rule out the occurrence of symptoms after a lactose load. Lactose is, indeed, responsible for symptoms in some IBS patients, however, these patients can only be identified by the occurrence of symptoms during the test, and not on the individual perception of milk intolerance.

Galactose consumption induces conditioned flavor avoidance in rats.

Recent findings revealed that intragastric infusions of galactose conditioned a flavor avoidance in adult rats. To determine whether the galactose-conditioned avoidance was due to the infusion procedure, we investigated the flavor conditioning effect of orally consumed galactose. Food-restricted rats drank a flavored galactose solution, a flavored fructose solution and a flavored saccharin solution in separate one-bottle training sessions; grape, cherry and orange flavors were used. Because fructose is sweeter than galactose, saccharin was added to the galactose solution to increase its palatability. Pre- and posttraining preferences for the galactose and fructose solutions were evaluated in two-bottle choice tests. Also, preferences for the sugar-paired flavors were evaluated in two-bottle tests with the flavors presented in saccharin. In Experiment 1, rats were trained with flavored 80 g/L fructose, 80 g/L galactose + 2 g/L saccharin, and 2 g/L saccharin solutions (20 mL/d). Their preference for the flavored galactose solution changed (P < 0.01) from 76% (pretraining) to 19% (posttraining). The rats also avoided (P < 0.05) the flavor paired with the galactose solution in choice tests with the fructose-paired flavor and the saccharin-paired flavor. Similar pre- to posttraining preference reversals were obtained in Experiments 2 and 3, which used 20 g/L galactose and fructose solutions, and 20 g/L galactose and fructose solutions mixed with 20 g/L glucose, respectively. These findings, together with the intragastric infusion data, demonstrate that galactose has aversive postingestive consequences in adult rats even at low concentrations (20 g/L). Unlike lactose intolerance, which is due to intestinal malabsorption, this galactose-induced flavor avoidance is presumably due to the slow and incomplete postabsorptive metabolism of galactose.

Anxiety and depression: a common feature of health care seeking patients with irritable bowel syndrome and food allergy.

BACKGROUND/AIMS: Irritable bowel syndrome (IBS) is a chronic disorder of the gastrointestinal tract. The etiology of IBS is still unclear and the relationship between foods and IBS is controversial; psychological factors have always been considered as a major cause of IBS and we recently showed a possible association via anxiety and depression between IBS and food allergy (FA). The aim of the present study was to confirm our preliminary observation. METHODOLOGY: Sixty-high IBS, 44 FA, 48 non-healthy controls with lactose intolerance (LI) and 52 healthy controls were considered for the study. All the subjects were given the State and Trait Anxiety Inventory and the Zung depression scale. RESULTS: The percentage of subjects with high levels of state anxiety, trait anxiety and depression was significantly higher in IBS than in both LI and healthy controls; psychological findings in patients with FA were very similar to those of IBS. There were higher levels of state anxiety in LI compared to healthy controls. CONCLUSIONS: A higher prevalence of state anxiety found in patients complaining of bowel symptoms could be linked to the presence of chronic ill status. The higher presence of trait anxiety and depression in IBS and FA patients could be responsible for an increase in the activity of the autonomic nervous system and could provoke motility alterations through mast cell mediator release as well as enhancing release due to allergen crosslinking with IgE at the mast cell surface. However, it is debatable whether psychological findings are characteristic of all IBS or FA patients, or just represent the subset that see physicians.

Allaying fears and fallacies about lactose intolerance.

Public awareness and misunderstandings of lactose intolerance are at an all-time high. Many people erroneously believe they are lactose intolerant or develop gastrointestinal symptoms after intake of lactose. Consequently, lactose-containing foods such as milk and other dairy foods may be eliminated unnecessarily from the diet. Because these foods are a major source of calcium, low intake of them can compromise calcium nutriture. This, in turn, can increase the risk of major chronic diseases such as osteoporosis (porous bones) and hypertension. This review is intended to help dietetics professionals alleviate clients' fears about lactose intolerance and recommend dietary strategies to improve tolerance to lactose. Scientific findings indicate that the prevalence of lactose intolerance is grossly overestimated. Other physiologic and psychologic factors can contribute to gastrointestinal symptoms that mimic lactose intolerance. Scientific findings also indicate that people with laboratory-confirmed low levels of the enzyme lactase can consume 1 serving of milk with a meal or 2 servings of milk per day in divided doses at breakfast and dinner without experiencing symptoms. Several dietary strategies are available to help lactose maldigesters include milk and other dairy foods in their diet without experiencing symptoms.

"Milk makes me sick but my body needs it": conflict and contradiction in the establishment of authoritative knowledge.

This article takes lactose intolerance as a topic for exploring clashes of power, authority, and knowledge in clinical interactions and interpretations of laywomen. In clinics providing maternal and child care, staff and clients jointly produced authoritative knowledge, most often a version of biomedicine. The Euroamerican staff tended to give advice that was biologically appropriate for them but not for many of their patients, a process reflecting what we refer to as biocentrism. Resulting information given to pregnant and lactating women and diagnoses of children's growth patterns were inappropriate in some cases, with potentially serious legal and health implications. Clinic staff often unwittingly ignored the efforts of their clients to begin a discussion of discrepancies between their bodily knowledge and clinic advice. Some women created their own syntheses, which supported the ascendancy of biomedical knowledge but were not in the interests of their own health.

Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance.

We reported previously that consumption of one cup of milk (240 mL) per day produced negligible symptoms in lactase-nonpersistent (LNP) individuals self-described as being severely lactose intolerant. We hypothesized that such LNP individuals could also tolerate two cups of milk per day if taken in two widely divided doses with food, and that psychologic factors play a role in perceptions of lactose intolerance. The Minnesota Multiphasic Personality Inventory 2 (MMPI-2) was administered to 19 LNP subjects self-described as markedly lactose intolerant (S-LNP), 13 LNP subjects who denied lactose intolerance (A-LNP), and 10 lactase-persistent individuals who believed they were lactose intolerant (S-LP). Symptoms were recorded when LNP subjects ingested 240 mL regular or lactose-hydrolyzed milk twice daily for 7 d in a double-blind crossover study. The results showed that neither LNP group had a significant increase in symptoms (P < 0.05) during the regular compared with the lactose-hydrolyzed milk periods. However, S-LNP subjects reported significantly greater gaseous symptoms than did the A-LNP subjects during both treatment periods. The MMPI-2 showed a high score on the "lie" validity scale for S-LNP subjects. We conclude that LNP subjects tolerate two cups of milk per day without appreciable symptoms. S-LNP subjects have underlying flatulence that is misattributed to lactose intolerance. MMPI-2 results were of questionable validity because of the high rate of dissimulation by LNP subjects.