A group of veterinary researchers at the University of California, Davis, has received an expression of concern for their May 2020 study on heart disease in dogs, for failing to adequately disclose conflicts of interest and for other aspects of the article.
The paper, “Development of plasma and whole blood taurine reference ranges and identification of dietary features associated with taurine deficiency and dilated cardiomyopathy in golden retrievers: A prospective, observational study,” appeared in PLOS ONE. The authors, from the lab of Joshua A. Stern, looked at the effects on the animals of “non-traditional” diets — those high in legumes but low in grains, which contain taurine, a key amino acid. Golden retrievers are known to be particularly vulnerable to cardiac problems associated with a lack of taurine. The FDA has been investigating the connection.
According to the authors:
Non-traditional diets, which were typically grain-free and contained legumes in this study, were significantly associated with and have increased relative risk for the identification of taurine deficiency and echocardiographic abnormalities consistent with nutritionally-mediated DCM. These findings were identifiable in the absence of clinical signs and support the findings of multiple previous studies and the ongoing FDA investigation.
But as the expression of concern indicates, the journal is considering walking back the paper.
For starters, the updated conflicts of interest statement is a far cry from the original, which reads:
A.J. Fascetti [Andrea Fascetti, one of the corresponding authors] is the Scientific Director of and J. Yu is employed by the Amino Acid Laboratory at the University of California, Davis that provides amino acid analysis on a fee for service basis. This did not influence the collection or interpretation of results in this study. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
Here’s the new one:
AJF is the Scientific Director and JY is the Technical Director of the Amino Acid Laboratory at the University of California, Davis (UCD) that provides amino acid analysis on a fee for service basis. AJF received remuneration for lectures or as an advisor on behalf of Nestlé Purina PetCare, Mars Petcare, Synergy Food Ingredients, the Mark Morris and Pet Food Institutes. AJF received funding from Nutro for graduate student training. A resident on the Nutrition Service, mentored in part by AJF, received funds from the Hill’s Pet Nutrition Resident Clinical Study Grants program, matched by the Center for Companion Animal Health, School of Veterinary Medicine at UCD. The Veterinary Medical Teaching Hospital at UCD received funding from Royal Canin to support a resident, and from Nestlé Purina PetCare to partially support a nutrition technician. AJF has a contract with the FDA on unrelated research. Since the time of article submission, JAS [Stern] has received research support from Nature’s Variety Inc. Collectively, this did not influence the collection or interpretation of results in this study. There are no patents, products in development or marketed products to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
Those omissions alone might well warrant retraction. But the notice also raises questions about several substantive aspects of the paper:
Concerns raised about the study are outlined below. The authors noted that some of these issues were discussed during pre-publication peer review and/or in the published article.
Questions were raised around the criteria used to categorize diets, including about the rationale of including global company sales details in these criteria given the objectives of the study.
Concerns were raised about potential confounds in the study, for example due to the inclusion of adult, puppy, and prescription-only foods, and due to inclusion of raw and kibble diets in the non-traditional group whereas the traditional group only included kibble.
Soybeans are in the legume family, but soybeans and soy products were not considered as legumes for the purpose of categorizing diets in this study. The authors have requested a correction to clarify that this was an intentional exclusion, and they have noted that this aspect of the study design aligned with how soy products are being handled in a related FDA investigation.
Questions were raised about the statistical analyses reported in the article.
Reporting errors were noted, including errors in Tables 1 and 2, for which the authors requested a correction, and other issues raised to the journal that may impact categorization of some included foods as traditional versus non-traditional.
Questions were raised as to whether three months on a given diet is a sufficient duration to impact cardiac/DCM outcomes, and whether diet history prior to a subject’s current diet may impact the study outcomes. Concerns were also raised about differences between groups in the average time on the current diet.
Questions were raised about the validity of the conclusion statement, “Grain free diets, produced by small companies, including legumes within the top 5 ingredients represent a risk for the development of taurine deficiency and echocardiographic abnormalities consistent with DCM in the golden retriever.”
The article [1] is being reassessed in light of issues raised post-publication, and the journal is investigating the validity of the concerns raised as well as their implications for the reliability of the article’s conclusions. Meanwhile, the PLOS ONE Editors issue this Expression of Concern.
Stern told us that he and his colleagues don’t believe the issues warrant retraction:
We stand by our work and do not believe the article should be retracted.
The expansion of the COI section on our article was the result of honest oversight. We responded to the query by expanding the COI section to include any possible perceived conflicts of interests. We remain committed to the statement that none of these disclosures impacted our data interpretation or conclusions.
We are thankful for the opportunity to work with the PLOSOne editorial team to evaluate the other concerns and hope that a resolution to these concerns will include our full response and rebuttal. We believe that all concerns can be addressed, do not change the outcome of the research and certainly do not warrant retraction of the work. We are confident that most of these concerns were adequately addressed during peer review and appear within the discussion and limitations section of the work. Several points are already addressed through a pending article correction that we provided to the journal prior to any expressed concern. Other concerns represent differences in scientific opinion that may be shaped by a number of factors including the letter writers’ own conflicts of interest or financial interests.
This study represents a sampling of feeding patterns in domestic pet golden retrievers. This of course leads to confounding variables that should be controlled and evaluated in future prospective laboratory feeding trial studies. We believe the list of limitations in the study is comprehensive and the data gleaned from this work remains relevant. Nutritionally mediated dilated cardiomyopathy remains an emerging and serious disease of growing concern in dogs. We are committed to scientific integrity and look forward to continued research in this area to better our understanding of this condition.
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The founder of the Facebook Groups that Dr Stern uses to interact with the public and gather data has long (and lucrative) relationships with the major supermarket dog food companies.