A re-appraisal of lactose intolerance

BACKGROUND

Lactose, beta-galactose-1,4-glucose, is hydrolysed by the enzyme lactase. Lactose intolerance occurs when lactase deficiency causes clinical symptoms.

AIMS

To provide an overview of lactose intolerance, including definition, aetiology and epidemiology, the clinical symptoms and diagnostic testing and management.

METHODS

A literature review was carried out to meet the aims of this paper. This resulted in the analysis of a database of patients tested for lactose intolerance to provide examples of the consequences of problems of terminology identified.

CONCLUSIONS

The terminology relating to lactose intolerance is confusing for clinicians and researchers. Clinicians need to ensure that these problematic terms do not cause diagnostic mistakes and inappropriate treatment. Researchers should be aware of inconsistent terminology in studies and resultant problems with the interpretation of results.

Molecularly-defined lactose malabsorption, milk consumption and anthropometric differences in adult males

BACKGROUND

Lactose malabsorption (LM) may be associated with reduced skeletal calcium content. Diagnosis to date has been based on indirect methods, with a high false-negative rate. Identification of the LCT polymorphism led to development of a PCR-based test.

AIM

To evaluate the PCR-based test compared to a combination the hydrogen breath test and the lactose tolerance test, and investigate anthropometrical differences, changes in bone mineral density and oral calcium intake according to LCT polymorphism and milk-drinking habits.

METHODS

All participants (n = 278) underwent clinical examination, with measurement of height, weight and bone density (DXA), and were genotyped for LCT polymorphism (LCT CC or LCT TT: CC is associated with LM). A subgroup (n = 51) had a hydrogen breath test and a lactose tolerance test, in addition to genotyping.

RESULTS

Detection of LM by LCT polymorphism was highly significant (p = 0.001). The correlation between LCT genotype and self-reported milk-intolerance or dislike of milk with was slight, but the correlation with functional tests was highly significant. Non-milk-drinkers were lighter (-5 kg) and significantly shorter (-4 cm) than milk-drinkers (p = 0.07 and 0.04, respectively). Total calcium consumption was lower among non-milk-drinkers by about 18% (p = 0.03).

DISCUSSION

Genotyping is an economic, quick and convenient method for diagnosing lactose malabsorption, with results comparable to existing tests. Sufficient calcium consumption may be relevant to body growth, as milk-drinkers were taller. Negative calcium bone balance may be prevented when provision is made for adequate calcium intake.

Temperature of a test solution influences abdominal symptoms in lactose tolerance tests

In lactose maldigesters, retarding gastric emptying (food/pharmaceuticals) improves tolerance to lactose. The role of temperature of test solution on the indicators of lactose intolerance was studied. After an overnight fast, 10 lactose maldigesters ingested, in three sessions, 50 g lactose in a randomized cross-over trial. The solutions were at temperatures of 20-21 degrees C (room temperature), 2-3 degrees C (cold) and 55-58 degrees C (hot). Gastrointestinal symptoms and indicators measuring lactose absorption were recorded. Abdominal pain was noticeably increased by the modification of temperature. The cold solution reduced flatulence and abdominal bloating, whereas the hot solution increased bloating and borborygmi. Breath hydrogen excretion tended to be augmented and retarded after cold solution. The temperature of the solution used in a lactose tolerance test affects the gastrointestinal symptoms, but has only minor effects on the other indicators of lactose maldigestion. The constant tendencies observed suggest that a room temperature solution is to be recommended for testing lactose digestion.

Poor predictability of lactose malabsorption from clinical symptoms for Chilean populations

Clinical symptoms and lactose malabsorption may occur in persons intolerant to lactose. To predict malabsorption from symptoms and age, the authors used simple regression, multiple regression, and discrimant analysis on data from 436 Chileans. All individual r2 values from simple regression were less than 0.05. For the best stepwise multiple regression program, R2 was only 0.09, indicating that 91% of the variability in malabsorption was "unexplained" by the five best predictor variables. Because of so much unexplained variability, the authors could detect (using multiple regression) only 56 of 90 (62%) malabsorbers and only 14 of 38 (37%) absorbers. In conclusion, for their Chilean populations the authors poorly predicted malabsorption from symptoms.

[Assessment of the lactose test and its value in detecting intolerance to milk sugar]

In 109 healthy and sick subjects suffering from diverse affections of the digestive organs the lactase activity in the mucosa of the large intestine was determined and a lactose test set up (1 g of lactose per 1 kg of body weight). In the test the following factors were considered: clinical symptoms, the rate of passage in the intestines (till the appearance of carmine), blood glucose content, pH and sugar in the feces. To appraise the activity of lactase the most accurate indicator in the test appeared to be the estimated degree of the rising blood glucose concentration as against the area of its ascent (23% of erroneous results). Because of a great variability of the test indicators the assessment of the lactase activity by combination of the latter did not increase the total number of correct results. However, in cases when there appeared combinations of indicators most characteristic for different activity of the lactase, the significance of the test results proved much higher (11.5-7% of erroneous results). Since in the lactose tolerance tests it is the total lactase activity, covering the entire surface of the small intestine that is recorded and subject to assessment are also possible changes, adaptive inclusive, of the gastro-intestinal tract motoricity, this test characterizes in the final analysis more correctly the tolerance of food products containing lactic sugar, than does direct determination of the lactase activity.