Associations between Body Mass Index and Semen Parameters among men from the Washington D.C. Metropolitan Area

Epidemiologic studies report associations between artificial sweetener (ASW) consumption and metabolic abnormalities, yet well-designed human intervention studies in humans are limited. Given that ASW contain no or few calories, one potential mechanism through which ASW may influence metabolic risk is through altering the gut microbiota. As alterations in the gut microbiota are known to be implicated in the development of metabolic disease, the purpose of this study was to investigate the effects of one week of three times daily diet soda (with ASW) consumption on the gut microbiota in healthy college students. We hypothesized that participants randomized to consume diet soda would have lower microbial diversity following consumption of diet soda, while microbial composition in the control group would be similar before and after the intervention. Healthy adults (n=22) were asked to provide a stool sample at three study visits, each one week apart. After the first visit, participants were instructed to avoid all ASW-containing substances for seven days (week 0). A second fecal sample was then collected (day 7), and a third was collected after one week of three times daily diet soda or carbonated water consumption (day 14) to evaluate changes in gut microbiota. DNA and RNA were extracted and samples were run on a single lane of an Illumina HiSeq. Metagenomics was performed using PathoScope™ and Censuscope™ and compared against a knowledgebase of normal gut microbiome data. Changes in read counts over the three time points were then compared between the two study groups. Twenty participants underwent randomization (n=11 diet soda, n=9 carbonated water), eighteen of whom completed the two-week study. While data analysis is ongoing, our preliminary data (n=2) suggest that ASW may in fact reduce microbial diversity. We observed a relative increase in species within the Bacteriodetes phylum and relative decreases in other phyla analyzed (Actinobacteria, Verrumicrobia, Proteobacteria, and Firmicutes) following diet soda exposure (n=1), but not following the carbonated water control (n=1). These preliminary data support our hypothesis that repeated ASW exposure may reduce the diversity of the gut microbiota and are consistent with findings of Suez et al., who also reported an increase in Bacteriodetes following saccharin exposure. However, a larger sample size and additional analyses are needed to confirm these findings. If ASW are found to adversely influence microbial diversity, this may have clinically relevant effects on metabolism, body weight, and health, which requires further study in humans