Journal Scan: In diet trials, don't forget about the flavoring

Why they did it

There is often concern that use of over-the-counter (OTC) products and medications during a dietary elimination trial may confound the results because of the presence of common proteins that are meant to be avoided during the trial. Dermatologists and nutritionists often recommend avoiding these OTC and flavored products during an elimination trial.

What they did

The researchers sought to determine if soy, beef, or pork antigens were present in flavored OTC products and veterinary therapeutics even when not listed in the ingredient list and whether these antigens could be identified by using enzyme-linked immunosorbent assays (ELISAs).

The authors evaluated three OTC products and four veterinary therapeutics. The products included flavored vitamin and mineral supplements, pill administration treats, heartworm preventives, and arthritis supplements. An unflavored vitamin and mineral supplement and three dry pet foods each containing soy, beef, or pork were used as the negative and positive controls, respectively. Samples of all products were sent to an independent laboratory to be evaluated for the presence of soy, beef, or pork antigens with ELISAs.

What they found

The beef, pork, and soy antigens were all documented via ELISAs in the positive control products. It confirmed the methodology would successfully detect the presence of these antigens. 

The researchers found that two test products-a heartworm product and an arthritis supplement-contained soy at 3.4 ppm and 9.2 ppm, respectively. The arthritis product listed soy derivatives on the ingredient list, but the heartworm product only listed therapeutic ingredients. Once the manufacturers were contacted, however, the researchers found that soy derivatives were also included. Four test products were positive for pork antigens, and two test products were positive for beef antigens. Some of these listed beef or pork in the ingredient list, but the antigen source was not clear for all products. For example, an arthritis supplement contained “gelatin,” which the manufacturer noted may be of either beef or pork origin. Another supplement listed “natural flavors,” which were determined to be of pork liver origin. Arthritis supplements containing “sodium chondroitin sulfate” were also found to be derived from bovine cartilage, but these tested negative for beef antigen.

Only a single product, the pill administration treats, did not contain any beef, pork, or soy antigen. This product was marketed as an “allergy formula.”

Take-home message

An educated owner may be successful in identifying the presence of certain antigens based on the ingredient list of OTC products. This may not be the case for veterinary therapeutic items. “The lack of information on other protein ingredients in the product inserts for therapeutic medications leads to confusion on the part of pet owners who cannot easily determine what common proteins are present in those products,” write the study authors.

Given this uncertainty with use of OTC or veterinary therapeutic agents, it will fall to the clinician prescribing the elimination trial to prescribe other non-flavored oral medications or topical therapy in order to decrease the risk of inaccurate trial results.

Parr JM, Remillard RL. Common confounders of dietary elimination trials contain the antigens soy, pork, and beef. J Am Anim Hosp Assoc 2014;50(5):298-304.

Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/25028437