That guilt-free treat may not be as innocent as it seems.  A new study suggests that alternative sweeteners commonly found in sugar-free and low-calorie foods and beverages may interfere with the growth of bacteria that help keep the gut healthy. But the effects aren’t always straightforward. Researchers found more than 100 cases where these ingredients behaved differently when combined with other substances — including one widely used antidepressant. That could be significant, given the gut microbiome’s far-reaching influence throughout the body.  The complex community of bacteria and other microorganisms living in your intestines plays a key role in digestion, immunity,…