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Pet Food Safety: Dietary Protein

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The goal of this article was to review the evidence surrounding the risks posed by insufficient or excessive dietary protein. Dietary protein is required to provide essential amino acids and replenish protein reserves. When intake is deficient, protein turnover slows and lean body mass is gradually depleted. These changes lead to increased morbidity and mortality. Dogs can maintain nitrogen balance (typically used to define minimum requirements in adults), yet be in a protein-depleted state due to physiologic adaptations. Preservation of protein turnover and lean body mass requires about threefold more protein than nitrogen balance. The ability of excess dietary protein to induce renal pathology was studied in both dogs with chronic kidney failure and older dogs without kidney failure. Numerous studies have confirmed that protein does not adversely affect the kidneys. However, phosphorus- and protein-restricted diets are clinically beneficial in dogs with existing chronic kidney failure. Protein restriction for healthy older dogs is not only unnecessary, it can be detrimental. Protein requirements actually increase by about 50% in older dogs, while their energy requirements tend to decrease. When insufficient protein is provided, it can aggravate the age-associated loss of lean body mass and may contribute to earlier mortality. Older dogs should receive at least 25% of their calories from protein, typically provided by diets containing at least 7 g protein/100 Kcal ME.

Section snippets

Remembering the Basics: Protein Metabolism

Dietary protein is predominantly a source of essential and nonessential amino acids. All proteins, whether dietary or endogenous, are made from the same 20 alpha amino acids. Ten of these, the essential amino acids, must be provided in the diet. The other 10 also are essential to the body for normal protein metabolism, but these can be produced endogenously via transamination, so are not considered dietary essentials. In addition to these, the beta amino acid taurine—which is not incorporated

What Are Minimum Protein Requirements?

Minimum nutrient requirements are defined as the lowest intake that will support normal function, such as maximal growth rates or prevention of deficiency signs. The minimum protein requirement for adults is typically defined, using a nitrogen balance study, as the smallest amount of a good quality protein that will maintain the subject in positive nitrogen balance after they have been allowed to accommodate to a low protein intake.3, 6 However, nitrogen balance does not account for changes in

What Is the Role of Protein Restriction in the Prevention and Management of Kidney Failure?

The primary concern regarding excess dietary protein has focused on the potential impact on kidney function. It was suggested by Brenner and coworkers that excess dietary protein would cause kidney damage, based on work in rats.16 While subsequent research suggested that the benefits attributed to protein restriction may have been secondary to the reduced calorie intake associated with low protein diets,17 the perception that excessive protein intake causes kidney damage remains.18 As noted

Safety of Protein for Senior Dogs

Many veterinarians have recommended protein restriction for older dogs in the belief that this would help protect kidney function.18 As identified above, this belief is unfounded. More recent research has unequivocally demonstrated that protein restriction is unnecessary, and potentially detrimental, in healthy, older dogs.7, 20, 41, 42 On the contrary, protein requirements actually increase by about 50% in older dogs, as noted previously.7

When dietary protein intake is insufficient, the body

Summary and Conclusions

Based on a comprehensive review, there remains no evidence that dietary protein causes kidney damage, or any other adverse effects, in healthy dogs. Even in dogs with chronic kidney disease, dietary protein does not appear to contribute to kidney damage. However, in chronic kidney disease, there can be an accumulation of byproducts of protein metabolism, which may contribute to uremic signs. Hence, in these patients, dietary protein restriction may be of benefit. On the other hand, dietary

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