Comparison of the Cariogenic Potential of Two Sweeteners, Stevia and Aspartame, Based on Bacterial Inhibition and pH Reduction

Background and aim Complete elimination of dietary sugars is impractical, especially for children. Restricting sugar intake and substituting sucrose with less cariogenic alternatives are plausible solutions. This in vitro study aimed to compare the cariogenic potential of two sweeteners, aspartame and stevia, by evaluating their bacterial inhibition capacity and the salivary pH changes produced at fixed time intervals. Methods To measure antibacterial activity, Petri plates containing 20 mL of Mueller-Hinton agar were seeded with a <i>Streptococcus mutans</i> culture adjusted to 0.5% McFarland Standard. Wells of approximately 10 mm diameter were bored using a well cutter, and different concentrations of the sweeteners (0.5%, 2.5%, 5.0%, and 10%) were added. Plates were incubated at 37°C for 24 hours, after which the zones of bacterial inhibition were measured. To measure pH changes, a test medium prepared by mixing artificial saliva (5 mL) with brain heart infusion medium (5 mL) was inoculated with <i>S. mutans</i> (50 µL). Samples were divided into two groups: stevia extract and aspartame. Increasing concentrations of both sweeteners were tested, and pH was recorded at regular intervals. Uninoculated test medium served as the control. Results Preliminary experiments were performed in single trials, followed by subsequent experiments carried out in triplicate to determine both pH changes and antibacterial activity of stevia and aspartame. The arithmetic mean of the observed values was used for statistical analysis. The zone of bacterial inhibition measured in millimeters and the pH change measured at varying concentrations of the two samples were compared using one-way ANOVA. The change in pH of various concentrations of stevia extract and aspartame recorded at different time intervals was compared using a paired t-test. The mean zone of bacterial inhibition was greater for stevia, and the area of inhibition increased with increasing concentration in both groups. No significant difference in pH change with increasing concentrations or time was observed between the aspartame and stevia groups. Conclusions Significant antimicrobial activity was exhibited by both aspartame and stevia against the cariogenic bacteria, <i>S. mutans</i>. The pH drop produced by both sweeteners over time also did not show significant differences under in vitro conditions. Hence, the findings suggest that aspartame and stevia possess comparable anticariogenic properties. Considering the calorific value and potential adverse effects of aspartame on human health, the natural sweetener stevia may be regarded as a better alternative.