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Canadian Journal of Gastroenterology
Volume 24, Issue 6, Pages 373-379
Original Article

Differential Impact of Lactose/Lactase Phenotype on Colonic Microflora

Andrew Szilagyi,1 Ian Shrier,2 Debra Heilpern,1 Jung Sung Je,3 Sunghoon Park,4 George Chong,4 Catherine Lalonde,1 Louis-Francois Cote,5 and Byong Lee6

1Division of Gastroenterology, Department of Medicine, McGill School of Medicine, Canada
2Centre for Clinical Epidemiology and Community Studies, Lady Davis Institute for Medical Research, Canada
3Department of Food Science, Macdonald Campus, McGill University, Canada
4Division of Laboratory Genetic Testing, Department of Biochemistry, Jewish General Hospital, Canada
5Department of Dietetics, Jewish General Hospital, Canada
6Department of Microbiology/Immunology, McGill University, Montreal, Quebec, Canada

Received 2 October 2009; Accepted 3 November 2009

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


BACKGROUND: The ability to digest lactose divides the world’s population into two phenotypes that may be risk variability markers for several diseases. Prebiotic effects likely favour lactose maldigesters who experience lactose spilling into their colon.

OBJECTIVE: To evaluate the effects of fixed-dose lactose solutions on fecal bifidobacteria and lactobacilli in digesters and maldigesters, and to determine whether the concept of a difference in ability to digest lactose is supported.

METHODS: A four-week study was performed in 23 lactose mal-digesters and 18 digesters. Following two weeks of dairy food withdrawal, subjects ingested 25 g of lactose twice a day for two weeks. Stool bifidobacteria and lactobacilli counts pre- and postintervention were measured as the primary outcome. For secondary outcomes, total anaerobes, Enterobacteriaceae, beta-galactosidase and N-acetyl-beta-D-glucosaminidase activity in stool, as well as breath hydrogen and symptoms following lactose challenge tests, were measured.

RESULTS: Lactose maldigesters had a mean change difference (0.72 log10 colony forming units/g stool; P=0.04) in bifidobacteria counts compared with lactose digesters. Lactobacilli counts were increased, but not significantly. Nevertheless, reduced breath hydrogen after lactose ingestion correlated with lactobacilli (r=−0.5; P<0.001). Reduced total breath hydrogen and symptom scores together, with a rise in fecal enzymes after intervention, were appropriate, but not significant.

CONCLUSIONS: Despite failure to achieve full colonic adaptation, the present study provided evidence for a differential impact of lactose on microflora depending on genetic lactase status. A prebiotic effect was evident in lactose maldigesters but not in lactose digesters. This may play a role in modifying the mechanisms of certain disease risks related to dairy food consumption between the two phenotypes.