Original article—alimentary tract
Subjective Perception of Lactose Intolerance Does Not Always Indicate Lactose Malabsorption

https://doi.org/10.1016/j.cgh.2010.03.027Get rights and content

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.

Section snippets

Experimental Design

Three hundred fifty-three white patients (113 men, 240 women; median age, 41 years) referred to our Digestive System Research Unit for evaluation of suspected lactose maldigestion by a hydrogen breath test (HBT) with lactose were prospectively studied after providing informed consent. None declined to participate in the study, had history of gastrointestinal surgery, or had taken antibiotics or been prepared for radiologic or endoscopic examinations for at least 2 weeks before entering the

Lactose Breath Test Assessment

Lactose HBT result was abnormal, delta increase over 25 ppm, in 164 of the 353 patients (46.4%). These patients were classified as lactose malabsorbers. Age and female predominance were similar in lactose absorber and malabsorber groups.

Perception of Lactose Tolerance

Results of each individual item and total score on the home and lactose symptoms questionnaire are shown in Figure 1. All items except vomiting scored significantly higher in the home questionnaire than in the lactose challenge questionnaire. Consequently, the

Discussion

There is extended belief among patients with abdominal symptoms that these are caused by lactose in dairy products. Indeed, lactose-free milk and related food products have become quite successful commercially. Lactase deficiency in adults is indeed relatively common among the Western population, but enzyme deficiency and symptomatic lactose intolerance are not tightly correlated. When individuals think that they are intolerant to lactose, they tend to avoid dairy products.18 However, when

Acknowledgments

The authors thank Miss Christine O'Hara for her valuable contributions to the English revision of this manuscript.

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    Conflicts of interest The authors disclose no conflicts.

    Funding This work was supported in part by grants from the Generalitat de Catalunya (RE: 2001SGR00389) and Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (Ciberehd, Spain). Ciberehd is funded by the Instituto de Salud Carlos III, Spain.

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