Failure of Activated Charcoal to Reduce the Release of Gases Produced by the Colonic Flora

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Failure of activated charcoal to reduce the release of gases produced by the colonic flora

"Objective:
Activated charcoal is used to treat excessive volume or malodor of intestinal gas. Our previous studies demonstrated that activated charcoal failed to bind appreciable quantities of the volumetrically important gut gases. However, the odor of feces and flatus derives primarily from trace quantities of sulfur-containing gases, primarily H2S and methanethiol, which should avidly bind to activated charcoal. The goal of this study was to determine if ingestion of activated charcoal reduces the fecal release of sulfur gases.

Methods:
Five healthy human volunteers ingested 0.52 g of activated charcoal four times daily for 1 wk and the fecal liberation of intestinal gases was measured before and after the activated charcoal treatment. In an effort to explain the in vivo results, additional in vitro studies were performed to compare the binding capacity of charcoal to the sulfur gas released by feces.

Results:
Ingestion of activated charcoal produced no significant reduction in the fecal release of any of the sulfur-containing gases, nor was total fecal gas release or abdominal symptoms significantly influenced. In vitro studies suggested that the failure of ingested charcoal to reduce liberation of sulfur gases probably is explained by the saturation of charcoal binding sites during passage through the gut.

Conclusion:
Commonly employed doses of activated charcoal do not appreciably influence the liberation of fecal gases."

From the discussion:

"In an effort to explain the failure of charcoal to reduce the fecal liberation of sulfur gases, additional quantitative studies were performed to compare the binding capacity of charcoal to the predicted sulfur gas release by feces. As shown in Figure 1, 1 g of dry charcoal bound about 787 mmol of H2S (17.6 ml/g). When wet, the adsorbing ability of charcoal was reduced to about 274 mmol/g. Inasmuch as our subjects ingested 2 g of charcoal/day, the maximal daily binding capacity of wet charcoal would have been about 548 mmol of sulfur gases. Before charcoal therapy, the sulfur gas production by the fecal material passed by our subjects averaged 9.75 ± 1.5 mmol/g dry weight. Assuming an average fecal output of 100 g per day and a dry weight of 30%, it can be estimated that the feces passed each day would produce about 293 ± 45 mmol of sulfur gas/24 h. This value is roughly 50–55% of the total capacity of the wet activated charcoal. Given that the binding sites of the activated charcoal in feces would be exposed to sulfur gases (as well as a variety of other compounds) during passage through the gut, it is not surprising that all binding sites had been filled by the time the feces reached the rectum."

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