Sulfites Abstracts 5

© 2013

Assessing the acute gastrointestinal effects of ingesting naturally occurring, high levels of sulfate in drinking water

         (Backer 2000) Download

Concerns regarding the health effects from sulfate in drinking water have been raised because of reports that diarrhea may be associated with ingesting water that contains high levels of sulfate. Of particular concern are groups in the general population (i.e., infants and transients) that may be at greater risk from the laxative effects of sulfate when they switch abruptly to drinking water with high sulfate concentrations. There have been a number of studies of the effects of sulfate in the drinking water of domestic animals (cattle, swine, and poultry), and most report minimal adverse effects from exposure to fairly high levels of sulfate. Anecdotal reports and case studies suggest that people suffer gastrointestinal effects when exposed to drinking water containing high levels of sulfate. However, there have been few experimental studies of the effects of sulfate on adults, and only two epidemiologic studies designed to assess the effects of high levels of sulfate on infants, and it is not yet possible to accurately determine the concentration of sulfate in drinking water that will produce adverse human health effects.

Microbial pathways in colonic sulfur metabolism and links with health and disease

            (Carbonero, Benefiel et al. 2012) Download

Sulfur is both crucial to life and a potential threat to health. While colonic sulfur metabolism mediated by eukaryotic cells is relatively well studied, much less is known about sulfur metabolism within gastrointestinal microbes. Sulfated compounds in the colon are either of inorganic (e.g., sulfates, sulfites) or organic (e.g., dietary amino acids and host mucins) origin. The most extensively studied of the microbes involved in colonic sulfur metabolism are the sulfate-reducing bacteria (SRB), which are common colonic inhabitants. Many other microbial pathways are likely to shape colonic sulfur metabolism as well as the composition and availability of sulfated compounds, and these interactions need to be examined in more detail. Hydrogen sulfide is the sulfur derivative that has attracted the most attention in the context of colonic health, and the extent to which it is detrimental or beneficial remains in debate. Several lines of evidence point to SRB or exogenous hydrogen sulfide as potential players in the etiology of intestinal disorders, inflammatory bowel diseases (IBDs) and colorectal cancer in particular. Generation of hydrogen sulfide via pathways other than dissimilatory sulfate reduction may be as, or more, important than those involving the SRB. We suggest here that a novel axis of research is to assess the effects of hydrogen sulfide in shaping colonic microbiome structure. Clearly, in-depth characterization of the microbial pathways involved in colonic sulfur metabolism is necessary for a better understanding of its contribution to colonic disorders and development of therapeutic strategies.

Intestinal effects of sulfate in drinking water on normal human subjects

         (Heizer, Sandler et al. 1997) Download

Uncontrolled observations implicate sulfate in drinking water at concentrations exceeding 500-700 mg/liter as a cause of diarrhea, but controlled studies have not been reported. We conducted a controlled study in normal adults to determine the effect of various drinking water sodium sulfate concentrations on bowel function. Ten healthy subjects were given a constant diet and fluid intake. Fluid consisted of 36 ml/kg/day of drinking water of various known sulfate concentrations and 500 ml of other fluid. In a dose-ranging study, four subjects received drinking water with sulfate concentrations of 0, 400, 600, 800, 1000, and 1200 mg/liters for six consecutive two-day periods. In a single-dose study, six other subjects received water with sulfate concentrations of 0 and 1200 mg/liter for two consecutive six-day periods. Stool mass, frequency, and consistency and mouth-to-anus appearance time of colored markers were measured. In the dose-ranging study, the only significant linear trend was decreasing mouth-to-anus appearance time with increasing sulfate concentrations. In the single-dose study, 1200 mg/liter sulfate caused a significant but clinically mild increase in mean stool mass per six-day pool from 621 g to 922 g (P = 0.03). When all 10 subjects were used to compare effects of 0 mg/liter and 1200 mg/liter sulfate, significant differences in stool consistency (P = 0.02) and transit time (P = 0.03) were observed. None of the subjects reported diarrhea or passed more than three stools per day. In 10 normal adult subjects, sulfate in drinking water at a concentration of 1200 mg/liter, which is higher than reported to occur in US municipal water sources, caused a measurable but clinically insignificant increase in stool mass and decrease in stool consistency and appearance time, but no change in stool frequency and no complaint of diarrhea.


References

Backer, L. C. (2000). "Assessing the acute gastrointestinal effects of ingesting naturally occurring, high levels of sulfate in drinking water." Crit Rev Clin Lab Sci 37(4): 389-400 PMID: 10983999

Carbonero, F., A. C. Benefiel, et al. (2012). "Microbial pathways in colonic sulfur metabolism and links with health and disease." Front Physiol 3: 448 PMID: 23226130

Heizer, W. D., R. S. Sandler, et al. (1997). "Intestinal effects of sulfate in drinking water on normal human subjects." Dig Dis Sci 42(5): 1055-61 PMID: 9149062