HARRISBURG, Pa. — Dr. Mehmet Oz rolled onstage inside of an inflatable orb, put on a hydrating face mask and proceeded to pitch a new line of skincare products to a convention of supplement distributors at Salt Lake City’s Vivint Arena in 2018. The crowd roared in applause.

The celebrity surgeon’s appearance seemed like an extension of “The Dr. Oz Show” on daytime TV. But his attendance was in service of the convention’s host, Usana Health Sciences, a Utah-based supplement manufacturer that has been investigated by federal authorities, sued by its own shareholders and accused of operating like a pyramid scheme.

Mehmet Oz Chris Pizzello/Associated Press, file

The company was also a top advertiser on Oz’s show, paying at least $50 million to be a “trusted partner and sponsor” featured in regular segments that often blurred the line between medical advice and advertising, while donating millions of dollars to Oz’s charity, according to records reviewed by The Associated Press.

Oz may have made his reputation as a surgeon. But he made a fortune as a salesman. Now he’s trying to leverage his celebrity as the Republican nominee in a bitterly contested U.S. Senate race in Pennsylvania.

The outcome of the race could turn on whether voters view Oz as the trusted doctor he portrayed on TV or a pitchman who repeatedly promoted products of questionable medical value.

“I like Mehmet Oz, but we did a lot of bull – when I worked there,” said Dr. Gregory Katz, a cardiologist and assistant professor at the New York University’s Grossman School of Medicine. He questioned whether viewers were healthier as a result of watching or “just wasting their money on bad supplements.”

Oz’s campaign declined to make him available for an interview. In a statement, the campaign said Oz’s show was “very diligent about disclosing” its “paid partners,” as required by federal regulation.

“I am very proud I was able to help so many people by bringing more transparency to health and wellness,” Oz said in a statement.

In a statement, Usana said any suggestion of wrongdoing was “misleading, incorrect or just false” and referred a reporter to statements the company has made in required disclosures to the Securities and Exchange Commission. The AP has reviewed those documents.

Oz, who stopped operating on patients in 2018, was a fixture on television, hosting his show for 13 seasons. It also led to a net worth that ranges roughly between $100 million and $315 million, according to a federal financial disclosure he filed this year.

How much Oz personally made from his agreements with Usana, or other advertisers is unclear. His financial disclosure reveals he earned a salary of $9.3 million last year.

In recent years, Oz was named in lawsuits that alleged he made misleading claims on the show, which ended its run this year after he announced his candidacy.

In at least one case, products Oz promoted have raised health concerns. Usana settled a California case in 2018 after a watchdog group discovered they contained unsafe levels of lead.

Oz entered into an arrangement with Usana in 2012, claiming publicly to have “meticulously” screened the company, which he praised for its “tremendous integrity.”

Under the agreement, Oz showcased a different Usana product each month while also selling company merchandise on his website. He also created promotional content for Usana, regularly joined company leadership calls and agreed to make appearances at company gatherings, records show.

The company, which is publicly traded, first drew attention from regulators in 2007 after a trader issued a report accusing it of operating as an illegal pyramid scheme.

The Securities and Exchange Commission, which regulates financial markets, investigated but took no action.

A year after reaching a deal with Oz, Usana in 2013 disclosed another SEC investigation over trading irregularities. No punitive action was taken.

The Justice Department and SEC investigated the company again in 2017 for possible violations of the Foreign Corrupt Practices Act – an anti-bribery law – in connection with a company subsidiary operating in China.

Usana said in a 2020 filing that the case was closed without enforcement action. An SEC spokesperson declined to comment on its investigation of the company.

In 2017, Usana entered into a settlement in California after a nonprofit group found unsafe levels of lead in 75 different products and flavors of powdered drinks, including their “Nurtrimeal” meal replacement shake. Oz featured some of the products on his show in the summer of 2015 and held a sweepstakes contest, including one that gave away 1,000 bags of the supplement.

In his Senate race, Oz has taken steps to put those connections behind him. Oz’s political advisers took over his website and removed footage that had been archived there, according to two former workers on the show who insisted on anonymity to discuss their experience because they signed nondisclosure agreements.

But some segments have been documented in news stories over the years.

In one, in 2015, Oz advised a woman who was concerned about her past partying to try a “liver detox supplement,” adding that Usana’s Hepasil could “reverse a lot of things that may have happened.” There is little clinical evidence to support the use of these diets, according to the U.S. Department of Health and Human Services.

Around 2005, Oz met Benson Boreyko, the founder of two marketing firms – New Vision International and Vemma Nutrition – that were sued by the Federal Trade Commission. In Oz promoted one of the Vemma’s products, while Boryeko served on the board of a nonprofit that Oz founded and Vemma was a donor.

The first FTC suit in 1998 was filed several years before Oz and Boreyko met and it targeted what it called unsubstantiated claims by New Vision International that the firm’s product could treat attention deficit/hyperactivity disorder. The second, in 2015, accused Vemma Nutrition of being an illegal pyramid scheme.

The companies settled in both cases, but admitted no wrongdoing. Company officials did not respond to repeated requests for comment.

Oz participated in various Vemma activities, including speaking at three of its annual conventions and joined marketing calls with the people who signed up to sell the products.