In a large group of men followed for 20 years, drinking regular soda and other sugary drinks often meant a person was more likely to get diabetes, but that was not true of artificially-sweetened soft drinks, or coffee or tea.
Replacing sugary drinks with diet versions seems to be a safe and healthy alternative, the authors said in The American Journal of Clinical Nutrition.
"There are multiple alternatives to regular soda," Dr. Frank Hu, one of the study's authors, told Reuters Health.
"Diet soda is perhaps not the best alternative, but moderate consumption is not going to have appreciable harmful effects," he said.
Prior studies have suggested that people who drink diet soda regularly might be more likely to get diabetes than those who stay away from artificially-sweetened drinks.
But this study indicates that the link is a result of other factors common to both diet soda drinkers and people with diabetes, including that they are more likely to be overweight.
In other words, people who are already diabetic or overweight are drinking more diet soda for those very reasons.