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Letters to the Editor |
Division of Gastroenterology Department of Medicine The Sir Mortimer B Davis Jewish General Hospital Montreal H3T 1E2 Quebec Canada
Dear Sir:
Recent publications downplaying the clinical significance of lactose intolerance notwithstanding, the study by Saltzman et al (1), which failed to show clinical improvement in subjects with lactose intolerance after treatment with Lactobacillus acidophilus BG2FO4, raises some interesting questions regarding colonic bacterial adaptation. Lactose and lactulose have been reported to improve lactose intolerance in formal studies (2, 3). The areas under the curve (AUCs) for breath hydrogen and symptom scores diminished and fecal ß-galactosidase concentrations increased after a period of exposure to either lactose or lactulose for 8 (1) to 16 (3) d. Furthermore, Hertzler et al (4) showed that the decrease in the AUC for breath hydrogen was due to decreased production and not to increased consumption of hydrogen. Because increased fecal ß-galactosidase concentrations would theoretically suggest an increased metabolic capacity to digest lactose, an observation of decreased hydrogen production is an unexpected finding. Thus, in studies using prebiotics, fecal ß-galactosidase may be more of a marker than a functional component of an expanded population of lactic acid bacteria.
Lactobacilli appear to behave differently depending on the species. Although changes in fecal bacterial enzymes are observed when lactobacilli are fed (5, 6), measured alterations in the AUCs for breath hydrogen vary with species (7). For example, Lin et al (7) found that L. bulgaricus improved the AUC for breath hydrogen and symptoms, whereas L. acidophilus did not. ß-Galactosidase characteristics, however, appeared similar with both species. Patients with a short bowel, but an intact colon, represent a natural example of functional bacterial colonic adaptation to carbohydrates. Briet et al (8) showed that such patients had already adapted to a challenge dose of lactulose compared with naïve, normal subjects. The triple feature of colonic adaptation (reduced AUC for breath hydrogen, improved symptoms, and elevated fecal ß-galactosidase concentrations) was easily discerned (8). In such patients the predominant fecal flora were lactobacilli of different species, including L. acidophilus (9). On the basis of these observations, one can question whether a different species of lactobacilli might not have given better results than L. acidophilus BG2FO4, whether a longer period than 7 d of exposure to L. acidophilus BG2FO4 might improve results (eg, in patients with short-bowel syndrome), or whether the clinical expression of colonic bacterial adaptation depends on interactions among several types of bacteria.
In any event, one conclusion to be drawn from the review of the literature is that prebiotics may be more efficient than probiotics in both achieving colonic bacterial adaptation and affecting lactose intolerance. However, both methods may ultimately have beneficial effects on colonic disease (reviewed in 10).
REFERENCES
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