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For more than 20 years, Dr. Martin C. Hinz has been an advocate and researcher in the use of nutritional products and urinalysis for people suffering from Parkinson's disease, depression and other maladies.

The 67-year-old Duluth native claimed in his most recent paper that the costly amino-acid treatments he says he invented work better than gold-standard therapy prescribed by neurology specialists.

But questions about that work have surfaced in recent months after the owner of Dove Medical Press, an academic publisher of peer-reviewed scientific and medical journals, retracted all six of Hinz's articles on Parkinson's. The six were among 20 papers on various diseases and lab techniques retracted because Hinz and his co-authors failed to produce raw data and medical ethics paperwork after not fully disclosing his and his family's business interests in sales of the costly pills.

It isn't the first time Hinz's theories and methods have drawn scrutiny and criticism.

In 2005 and 2011 he received warnings from the Food and Drug Administration (FDA) for marketing untested nutrients as drugs. Last year, the Minnesota Board of Medical Practice reprimanded him for false advertising, unethical conduct and fee splitting. The board restored Hinz's Minnesota medical license to full standing in November after he paid a $7,188 civil penalty.

Hinz, who lives in Florida, maintains his journal articles were stricken from the record on a technicality — a missed deadline by a co-author — and that his underlying scientific conclusions remain valid.

"I think that every reader is allowed to come to their own conclusion," Hinz said, defending his work. "The peer review was never attacked. The science that we put on paper was never attacked. … With these papers, I don't think we did anything wrong."

Hinz's most controversial claim is that carbidopa — a component of the prescription Sinemet, the mainstream treatment for Parkinson's — is associated with greater death rates from the disease.

He continues to stand behind the claim, as shown in a May 2021 pamphlet provided to the Star Tribune. His tone has shifted to reflect the FDA's insistence that nutritional products costing hundreds per month can't be sold as "treatments" without first doing a clinical trial.

"We treat nothing," Hinz wrote in an e-mail. "We claim to treat nothing with nutrients."

One doctor familiar with Hinz's work said the decision to retract the articles points to a longstanding problem — Hinz has never run a randomized clinical trial to prove his claims.

"I have seen no evidence, nor does my ... understanding of Parkinson's explain to me why [Hinz's] protocol would work," said Dr. Matthew Markert, a neurologist and researcher with Stanford University. But "to fail to provide the opportunity for a potentially superior treatment to undergo the scrutiny of randomization and blindedness is a tragedy, and harmful to all the people who would benefit."

Asked about Hinz's current business activities, an FDA spokesperson declined to comment, saying, "The FDA does not comment on ongoing investigations."

Making his case

Though he runs a company called NeuroResearch Centers and has assembled a database he says contains more than 1,200 Parkinson's patients, Hinz is a family practice physician and not a neurologist.

After leaving the Air Force in 1976, he graduated from the University of Minnesota Medical School in 1983, and opened his practice in Duluth's Morgan Park neighborhood a decade later. Not long after, he began prescribing the controversial "fen-phen" drug combo for weight loss.

Hinz said prescribing phentermine — one of the two drugs in "fen-phen" — led to his discovery that amino acid supplements can restore neurotransmitters depleted by drugs like phentermine or diseases such as Parkinson's.

Hinz proposed taking amino acid supplements, since they can convert into dopamine, serotonin and other neurotransmitters inside the body, addressing what he would come to see as nutritional deficiencies, including low dopamine levels causing impaired movement and other symptoms in Parkinson's.

Hinz began building a database of de-identified patient data. He documented results using lab tests performed by former St. Louis County medical examiner Dr. Thomas Uncini, a personal friend. The data, drawn from patients across the country, would serve as the clinical evidence for a series of papers Hinz, Uncini and several other collaborators authored.

The papers, which Hinz paid $2,000 to $2,500 apiece to publish and can still be read online even though they are marked "retracted," explained Hinz's theory that a range of health problems stem from "relative nutritional deficiencies," which can be addressed with supplements and urine testing.

One 2011 paper described "a novel approach for the treatment of Parkinson's disease" by taking a substance called L-dopa, contained naturally in the Mucuna pruriens bean, plus amino acids including L-tyrosine, L-cysteine and 5-HTP.

In a 2016 article, Hinz claimed his treatment was superior to prescription drugs for Parkinson's like Sinemet, which combines the drug form of L-dopa with a second drug called carbidopa. Two years earlier, he and his co-authors claimed that carbidopa may have contributed to a 329% increase in the population-level death rate from Parkinson's since it came into wide use in 1976.

"These drugs can create fatal events, clinical deterioration, drug-induced [health problems], and risks where none previously existed due to profound multi-system nutritional collapse," they wrote.

Benefits of carbidopa

Dr. David McKee, a neurologist in Duluth, said those statements about the risks of carbidopa are simply wrong. One of the drug's key benefits, he said, is prevention of nausea by delaying the conversion of L-dopa into dopamine outside the brain.

"Carbidopa was a godsend," McKee said. "It prevents the breakdown of levodopa in the gastrointestinal tract, so … a higher percentage of it makes it to the brain."

For Malcolm Hughes, a 63-year-old landscape artist in Charlottesville, Va., adding carbidopa to his treatment regimen for Parkinson's allowed him to reduce his overall quantity of L-dopa twelvefold from what he'd been taking under a protocol designed by Hinz. That eliminated the recurrent and often-severe nausea he said he suffered after taking the amino acid pills, which cost him roughly $8,000 annually.

Today, Hughes takes prescription Sinemet, which he gets for $1,300 a year.

"It's an … affordable, inexpensive drug that I buy generic at Sam's Club. I can't believe the difference," Hughes said. "It's just been a wonderful improvement."

Hinz declined to identify any customers or providers who would speak to the benefits of his supplements.

Questionable claims

Stanford's Markert has reviewed Hinz's published work and said he found it unconvincing. He said Hinz's claims about Parkinson's are impossible to assess because there's never been a randomized clinical trial.

"This has nothing to do with him. This has to do with any claim in medicine," Markert said. "If someone is going to stand up and say, my method is … superior, any superiority claim must undergo the rigor of randomization, period."

Hinz said he has never done a randomized, blinded clinical trial because that's not required by the FDA for products containing only nutrients.

"I stand by the fact that we meet the FDA requirements," Hinz wrote in an e-mail.

Hinz said in an interview that clinical trials "are incredibly expensive, incredibly time consuming things ... For what I need, I know that it works."

Uncini, a pathologist who co-authored 14 of Hinz's papers, said he was convinced Hinz's supplements had some effect. But he also thinks Hinz should do a randomized clinical trial to prove it.

"Those supplements changed the lab results. That's all I know," Uncini said. "Whether they work to relieve symptoms or anything else — I wasn't a part of that. …

"I personally don't use them. I've had family members with Parkinson's. I did not have them contact Dr. Hinz."

Financial conflicts

Hinz's work centers around three companies he started — NeuroResearch Clinics in 2002; DBS Labs, with Uncini as medical director, a year later; and West Duluth Distribution Co., doing business as CHK Nutrition, in 2005. CHK sells the supplements used in Hinz's research.

When they were founded, each business was located in the same small Duluth medical clinic. NeuroResearch and DBS were moved to Florida in 2010, but CHK remains in Duluth in an unmarked warehouse behind a bar and grill.

In 2005, the FDA sent Hinz a warning letter saying Neuro­Research must stop illegally marketing amino acids to treat symptoms of depression, obesity, pain and Parkinson's, among other things.

Then, in 2011, the FDA filed a civil complaint against Hinz and NeuroResearch Clinics, along with CHK and Hinz's daughter, Amy, who had become CEO of CHK. The complaint alleged they were illegally distributing amino acid products as drugs to cure or treat diseases without evidence showing they worked.

The lawsuit was eventually resolved, without any admission of wrongdoing, through a settlement. As part of the settlement, the FDA can conduct unannounced inspections of CHK Nutrition.

Hinz says he has lawyers review everything he does.

Yet in March 2020, the Minnesota Board of Medical Practice reprimanded him for not disclosing all of his economic interests in CHK, DBS and NeuroResearch to patients or other doctors. It also cited a 2018 FDA warning accusing Hinz of continuing to promote CHK products as drugs.

Hinz told the Star Tribune that CHK Nutrition pays a 43% royalty on gross sales of nutritional products he invented. That royalty goes to NeuroResearch, which pays Hinz.

"I invented this stuff," he said. "I licensed CHK to sell it."

Missed deadline

Amid criticism of his claims and methods, Hinz argues his 20 articles were invalidated simply because a co-author, now-retired University of Minnesota biomedical researcher Dr. George Trachte, was gravely ill when the journals' publisher demanded proof that patients didn't need to consent to research using their de-identified data. Hinz said Trachte missed the deadline by two days.

Trachte, a Duluth resident, declined to comment on the issue.

The papers appeared in seven medical journals, all published by Dove Medical Press before Dove's 2017 acquisition by Taylor & Francis Group.

"George Trachte did send some documents after the deadline for a response had passed, but these didn't answer all the issues under investigation," said Taylor & Francis spokeswoman Elaine Devine. "The documents he did send were also not applicable to all the articles. We did not refuse to acknowledge these documents."

Hinz blames the journals for failing to initially ask for a "certificate" of approval from an Institutional Review Board (IRB), which is a panel that examines ethical questions involving research on humans.

"The real problem here was Dove Press published 20 papers without IRB certificates, without asking for them, without anything," Hinz said. "And then when they realized it wasn't there, they turned it on us."