Panel Discussion: The Role of Dietary Copper in Chronic Hepatitis

Presentation Description / Summary   

Panel discussion explores the concern that dietary copper in some commercial dog foods exceed tolerance of many dogs and is causal to the increased diagnosis of copper associated hepatopathy (CAH) over the last 25 years. Mean hepatic copper concentration in dogs has progressively increased from < 10 μg/g (dry weight basis) in 1929 to 200 μg/g in 1982, coincident with popularization of commercial dog foods. Values increased to 453 μg/g in 1995 and now frequently exceed this concentration in canine liver biopsies. Copper content of commercial dog food was suspected to have escalated hepatic copper concentrations since early1980 when Bedlington Terrier CAH was initially characterized. In 1997 the NRC recommended a change from food grade copper oxide (recognized as having low bioavailability) to more bioavailable forms of copper (copper sulfate, protein chelates). This recommendation was based on a brief abstract (no peer reviewed manuscript) of a study conducted in growing dogs. Findings corroborated low bioavailability of copper oxide and concluded that the then established NRC standard of 0.8 mg bioavailable copper/1000 kcal ME failed to meet copper requirements of dogs (growing dogs studied). Mineral analysis of the studied diet nor its formulation were declared. Dietary guidelines are generally developed from nutrient recommendations made by an NRC panel of experts, on the basis of evidence-based scientific studies.  In this case, there was meager evidence. Currently, NRC & AFFCO support use of a premix to assure adequate dietary copper content in maintenance commercial dog food. There is no consideration of baseline dietary copper content. A survey of over-the-counter dog foods in 2013 demonstrated some egregiously supplemented diets. Consumers have no way to discern what diets might be over-supplemented as the bioavailable copper content is not declared on pet food labels. Therapeutic diets for dogs with hepatic insufficiency or CAH contain less than 50% of the median copper concentration present in maintenance foods that are commonly fed to dogs.  These copper restricted diets have been used for the lifetime of dogs with copper associated hepatopathy, congenital portosystemic shunts, as well as clinically normal dogs, without any evidence suggestive of copper deficiency. The panel discussion is meant to stimulate audience participation in strategizing a way to provide the FDA with data that will instigate corrective measures. This problem is currently sidelined by a declared lack of evidence of a safe upper limit for copper in dog food.