The release of a 2006 study that linked zinc poisoning from denture cream to neuropathy was delayed for nearly two years because one of its reviewers cast doubt on its conclusions. But according to a report that aired this morning on Good Morning America, that reviewer, Dr. Kenneth Shay, a dentist, had a conflict of interest. He was a paid consultant for Procter & Gamble, the maker of zinc-containing Fixodent denture cream.
The study in question was finally published in 2008 in the journal Neurology. The article reported on four patients â€“ all of whom used excessive amounts of zinc-containing denture cream – suffering from neuropathy and other neurological symptoms typical of zinc poisoning and copper depletion. The study concluded that excess use of denture cream could have been responsible for their symptoms.
The human body does need zinc â€“ but only in small amounts. Studies show that consuming at least 50 milligrams of zinc a day for a few months could lead to copper deficiency, which can cause anemia, bone loss, nerve damage and other problems. Ingesting 80 or 100 milligrams or more for months or even years can lead to irreversible damage.
In reviewing the Neurology study, Dr. Shay discounted its conclusions. According to Good Morning America, Dr. Shay called the link between excessive use of denture cream and neurological disease “little more than speculation.” He said that the authors “don’t understand the nature of the material they are writing about.”
Shay not only made recommendations that the study authors say led them to water down the its finding, but also sent draft reports of the study to Procter & Gamble, Good Morning America reported. In one e-mail, he said, “Please be circumspect because, as a reviewer, I’m not supposed to be passing an unpublished manuscript around.”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’s not clear what Procter & Gamble did with the information.
“It is an outrage. This was wrong,” David Rothman, a professor at Columbia University Medical School, told Good Morning America, in regards to Dr. Shay’s conduct. “That is a fundamental transgression of professional medical ethics and not to be allowed.”
Dr. 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.”
As we’ve reported previously, in March 2010, Procter & Gamble began cautioning consumers about zinc in Fixodent denture creams on it website, www.dentureliving.com. The new information stated that some reports suggest that excessive and prolonged zinc intake may be linked to adverse health effects. At the same time, Procter & Gamble also began shipping Fixodent with updated label instructions on how to apply the product. The zinc, however, remains in Fixodent.
But a month prior to that, after some Super Poligrip users had filed lawsuits alleging zinc poisoning, GlaxoSmithKline announced it would stop the manufacture, distribution and advertising of three Super Poligrip products that contained zinc. In a statement posted on its website, Glaxo said it was reformulating the Super Poligrip products as a precautionary measure to minimize any potential risks to consumers.
At least one law firm representing plaintiffs in denture cream poisoning lawsuits filed against Procter & Gamble said at the time that the company didn’t go far enough. In a statement, New York-based Parker Waichman LLP said that the lack of a clear warning combined with ambiguous instructions for use only serve to enhance the danger faced by consumers.
“While any new caution regarding Fixodent is a step in the right direction, it does not go nearly far enough,” said Andres Alonso, a partner of Parker Waichman. “Procter & Gamble’s attempt to do this quietly will leave too many consumers unaware of the danger that Fixodent could pose to their health. As long as these products continue to be sold, they remain a serious public health threat.”