To the Editor: On reading Dr Lin’s discussion of the hypothesis of small intestinal bacterial overgrowth (SIBO) as a framework for understanding irritable bowel syndrome (IBS),1 I have concerns that the only data put forward are at best indirect, and that alternate conclusions could be drawn from the given findings.
Our report of whole-body calorimeter measurement of 24-hour excretion of hydrogen and methane2 (reference 19 in the article) is referred to incorrectly. Higher hydrogen volumes and 4-fold greater maximal rates of excretion were observed in patients compared with controls, all of whom were eating the same “standard Western diet,” not following lactulose ingestion as was stated. Patients and controls were provided identical food for 14 days prior to measurement, with 3-day rotation of fixed diet. The second reported study from the same group3 (reference 21 in the article) used the same methodology, which is also misstated. Whole-body excretion of hydrogen and methane after lactulose has, to my knowledge, not been studied in IBS patients but would require a prolonged period of measurement, perhaps 18 hours.4
The maximum rates of gas excretion observed in IBS patients in our study were very high and comparable with maximum rates found in a study of whole-body hydrogen excretion following lactulose in pneumatosis cystoides intestinalis4 (where local accumulation of hydrogen gas in the tissues suggests that the site of production is the colon). That study reported absence of hydrogen-consuming colon flora.
Logic principles suggest an argument is more strongly supported by a (failed) attempt to disprove it, rather than a framework of weakly supportive strands. Methods have been described allowing anatomical location of a swallowed bolus of lactulose (by scintigraphy) and confirmation that an observed hydrogen excretion coincides with fermentation of lactulose, rather than other moieties (conversion of 14C/13C lactulose to 13CO2/14CO2). These would seem appropriate studies given the interest the hypothesis has generated. Previous evaluation of lactulose hydrogen breath tests using such methods has generally revealed woeful inadequacy of the measurement of hydrogen alone.5
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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