Mannatech is a publicly traded, multinational multi-level marketing firm that sells dietary supplements and personal care products. It was founded in November 1993 by Samuel Caster, and is headquartered in Flower Mound, Texas. The company's stock is traded on the NASDAQ exchange under the symbol MTEX. As of 2017, Mannatech employed 252 people and sold its products through some 220,000 independent sales associates.
In 2007, Mannatech and its salespeople made false claims of anti-disease benefits about its lead product called "Ambrotose" which contains sugars derived from plants. The company was profitable soon after its founding until about 2008, when it started losing money due to exposure of its business practices through a class action lawsuit based on the false health claims, a critical 20/20 news special, and a civil suit filed by the Attorney General of Texas.