For decades, artificial sweeteners have been promoted as a healthier alternative to sugar. But new research suggests they may come with unexpected effects on your metabolism.Researchers analyzed 21 randomized clinical trials comparing artificial and low-calorie sweeteners with non-caloric options like water or a placebo.The results: artificial sweeteners were linked to higher fasting insulin levels and a higher HbA1c—a measure of long-term blood sugar control.The analysis also showed a trend toward reduced insulin sensitivity.Researchers say one possible explanation involves the gut microbiome. Previous evidence suggests certain non-nutritive sweeteners can alter the makeup and function of your gut bacteria.The review also found that people who consume more artificial sweeteners may have a higher risk of cardiometabolic conditions, including type 2 diabetes and heart disease.The researchers say their overall findings suggest these compounds may have metabolic harms. More studies are needed to establish cause and effect.In the meantime, the senior author says. “If you’re replacing large amounts of added sugar in your diet, such as in multiple servings of soda, these low-calorie sweeteners may be a better alternative.”But he adds, "We can't simply assume they are safe and innocuous, and avoiding them whenever possible appears a prudent choice."Source: Current Atherosclerosis ReportsAuthor Affiliations: Friedman School of Nutrition Science and Policy, Tufts University, Food Is Medicine Institute.Sign up for our weekly HealthDay newsletter