 Over 2008 to 2017, the US Food and Drug Administration issued several warning letters to manufacturers of dietary supplements containing EGCG for violations of the Federal Food, Drug, and Cosmetic Act.Most of these letters informed the companies that their promotional materials promoted EGCG-based dietary supplements the treatment or prevention of diseases or conditions that cause them to be classified as drugs under the United States code, while another focused on inadequate quality assurance procedures and labeling violations.The warnings were issued because the products had not been established as safe and effective for their marketed uses and were promoted as "new drugs", without approval as required under the Act.