[1] 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.

[2][3][4] 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.

[6] The company has had a Christian orientation since its founding; the name was intended to evoke manna, and it recruited people to sell its products through its multi-level marketing structure in church congregations.

The IPO raised $12 million in funds to be used for expansion into Australia and the U.K.[13] The company came to be known for unproven claims that its products could be used to treat many diseases and conditions, including cancer, diabetes, autism and AIDS.

Following patient complaints about her marketing of the products in 2006, Balonwu was dismissed by her employer, Harmoni, a medical services company, and the GMC panel imposed a 15-month penalty period during which she was "to avoid private or short term locum work" and "to complete a supervised personal development plan to tackle shortcomings in her practice".

[27] In July 2006, Texas Attorney General Greg Abbott formally charged Mannatech, MannaRelief, Sam Caster, and Reginald McDaniel, the company's medical director, with operating an illegal marketing scheme in violation of state law.

[28][29] A 20/20 undercover investigation that aired June 1, 2007 on ABC Television showed Mannatech's sales associates teaching sales recruits how to target Mannatech products to people with specific illnesses in a manner that purportedly does not violate U.S. federal law, including U.S. Food and Drug Administration regulations, by avoiding direct claims that the products cure any particular diseases.

[30] In October 2007, it was reported that the company had fired Grant Thornton LLP as its auditor after the accounting firm demanded that Mannatech remove Caster from all responsibilities[30][31] to be replaced by Wayne Badovinus as the new chief executive.

In addition, Sam Caster agreed to pay a $1 million civil penalty and steer clear of any type of leadership position or employment relationship with Mannatech for five years.

[51] In November 2015, Mannatech said on its website that, for compliance with Federal campaign finance regulations, the company had removed all references to Carson before he announced his bid for the presidency.