The maximum recommended daily dose of stevia is 4 milligrams per kilogram of body weight. Both the World Health Organization and the European Food Safety Authority use this as their safety standard for stevia. The United States has no official guidelines on what amount of stevia is considered dangerous, so these measurements are only available in the metric system.
Stevia is South American plant used to produced a calorie-free artificial sweetener. Both unprocessed leaves and processed extracts are used as sweeteners. Stevia is most popular in Japan, where 40 percent of artificially sweetened products use stevia.
Pure stevia is not an approved food additive in the United States. One of the chemical components of stevia, Rebaudioside A, is classified as generally recognized as safe by the Food and Drug Administration. This approved additive is used in artificial sweeteners. Whole stevia leaves and other forms of unrefined stevia cannot be sold as food products in the United States. They can be sold as dietary supplements.
The Mayo Clinic cites concerns about stevia's effect on blood sugar control, kidney function, cardiovascular help and the reproductive system. These concerns are why the Food and Drug Administration has not approved unrefined stevia for sale in the United States.