Why is Ben Carson plugging a sketchy supplements seller?

Last Updated Oct 29, 2015 4:52 PM EDT

During Wednesday night's Republican presidential debate, Ben Carson put in a plug for Mannatech (MTEX), even while dismissing as "propaganda" the suggestion he had ties to the seller of nutritional supplements, which has a questionable track record that included claims its products could cure Downs syndrome, cystic fibrosis and cancer.

Asked why he continued to be involved with the company even after it paid millions to settle a deceptive marketing lawsuit in Texas, Carson said: "That's easy to answer. I didn't have an involvement with them. That is total propaganda."

"I did a couple of speeches for them," the retired neurosurgeon went on to say. "I do speeches for other people. They were paid speeches. It is absolutely absurd to say that I had any kind of relationship with them. Do I take the product? Yes, I think it's a good product."

In an emailed reply to a request for comment, Mike Crouch, Mannatech's director of communications, called Carson's words "a true statement and clearly defines the limits of his relationship with the company." The GOP White House hopeful is a "long-term customer and has spoken about his personal and professional experiences at Mannatech events."

Carson was paid $42,000 to speak at a company event in 2013, while speaking fees for three prior events were donated to the Carson Scholars Fund, Crouch said.

In 2004, Carson told a gathering of Mannatech sales associates that the company's products helped cure his own prostate cancer, saying in a company video: "within about three weeks my symptoms went away, and I was really quite amazed."

The company's events often feature testimonials making claims that the company's products have "cured, mitigated, treated, or prevented diseases," according to a 2007 petition filed by the Texas Attorney General that accused the company of deceptive marketing. "The whole purpose of the testimonials is to create a frenzy and motivate associates to see even more products, in large part through the relaying of deceptive claims set forth in the testimonials."

Coppell, Texas-based Mannatech earned $6.5 million in 2014 on revenue of $190.1 million. It claims "glyconutrients" in its products contain sugars that bolster immune and digestive function.

Mannatech's business model involves multilevel marketing, a type of direct selling by independent associates not employed by the company, who purchase Mannatech's products to resell or for personal use. A regulatory filing in August said 228,000 associates or members in two dozen countries had purchased its products within the last 12 months.

Other multilevel marketing companies include Nu Skin Enterprises (NUS), Avon Products (AVP) and Herbalife (HLF). Some, most notably Herbalife, have faced claims they are pyramid schemes. According to the U.S. Securities and Exchange Commission, a pyramid scheme is a form of fraud in which "participants profit almost exclusively through recruiting other people to participate in the program."

Mannatech's website includes stories of individuals around the globe that have earning more than $1 million since they began working with the company, including the formerly stressed single mom working three jobs in Australia, who is now able to afford holidays and travel.

"Basically what the company is doing is trying to find a way to restore natural diet as a medicine, or as a mechanism, for maintaining health," Carson said in one Mannatech video. "That's why I was drawn towards Mannatech because it recognized the influence on health of natural foods."

Dietary and nutritional supplements do not require approval by the FDA to be sold in the United States, due to the Dietary Supplement Health and Education Act of 1994.

"Carson chose to participate in videos while attending corporate events, where he gave his personal perspective and testimony," said Crouch, who reiterated the candidate was not a spokesman for the company nor a "paid endorser."

In March of 2014, Carson shot a PBS special touting "glyconutrients" in a similar vein as he had done in the company's videos.

Under a 2009 settlement with the Texas attorney general, Mannatech agreed to stop false claims that included pitching its products as cures and treatments for a number of serious illnesses. The company agreed to pay $4 million in restitution to Texas consumers, and its founder paid a $1 million civil penalty.

"Texans will not tolerate illegal marketing schemes that prey upon the sick and unsuspecting," Greg Abbott, the state's attorney at the time and current governor, said in a statement announcing the accord.

The Texas AG's civil complaint said the company had been notified multiple times by the U.S. Food and Drug Administration that its marketing materials made illegal drug claims.

Carson's campaign did not return a request for comment.

The White House hopeful is not the first well-known physician to endorse nutritional supplements backed by questionable science. Dr. Mehmet Oz last summer was called before Congress to testify at a Senate hearing about deceptive advertising for over-the-counter diet supplements after he touted green coffee bean extract as a "miracle" weight loss pill.