But an ABC News investigation found that that Shay, at the time, also was a paid consultant to Procter & Gamble, the maker of Fixodent, when he reviewed the study.
"It is an outrage. This was wrong," David Rothman, a professor at Columbia University Medical School, told Cuomo. "That is a fundamental transgression of professional medical ethics and not to be allowed."
In e-mails and documents obtained by ABC News, Shay not only made recommendations that, according to the authors, led them to water down the study's finding, but also sent draft reports of the study to Procter & Gamble.
In one e-mail, he said, "Please be circumspect because, as a reviewer, I'm not supposed to be passing an unpublished manuscript around."
It is unclear what, if anything, Procter & Gamble did with the information Shay passed on to it.
It wasn't until 2009, after the study was published in the journal Neurology, that Procter & Gamble added a "new label information" warning to the side of Fixodent packages, and on the back, cautioned that "prolonged zinc intake may be linked to adverse health effects."
Shay declined to be interviewed, but in a phone call with ABC News he defended his review of the study, saying that the research report had "objective shortcomings."
Procter & Gamble sent a written statement to ABC News reading:
"Procter & Gamble is committed to providing safe and effective products for all consumers. That is who we are and what we stand for. We go to great lengths to ensure that our products safely deliver best-in-class performance, so consumers can choose our products with total confidence. Fixodent is safe for use as directed, as supported by the experience of millions of consumers over many years. Our Fixodent formula has undergone extensive scientific testing, and we continuously monitor for its safe use. ... We know of no valid scientific evidence that using Fixodent as directed causes any ill health effects."
But Mark Jacoby and others like him said it all comes too late. He has stopped using Fixodent, but said the damage to his body has been done.
"Fixodent and forget it?" said Jacoby. "Well, apparently I can't forget it 'cause it took a lot away from me."
If you have suffered from adverse reaction to Fixodent, send your story to Chris Cuomo.