How Dogs Age: What a New Study Reveals — And Why Treat Quality Matters
A landmark study using data from the Dog Aging Project reveals how dogs age at the molecular level — offering new insights into how the body uses protein, how it processes nutrients, and how this changes the way we should think about dog treats.
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Researchers have shed new light on the ageing process in dogs and opened a window into how they use proteins, process nutrients, and maintain metabolic balance—critical functions for long-term health. Scientists from Tufts University and the University of Washington analysed blood samples from nearly 800 dogs participating in the Dog Aging Project. The project studies ageing in companion dogs to uncover insights that benefit both dogs and humans, since we share similar environments, lifestyles, and age-related diseases.
The researchers discovered that nearly half of the measurable chemical compounds in a dog’s bloodstream shifted as the dogs grew older — evidence that ageing affects the body’s entire metabolic network, not just a few organs. These tiny chemical shifts show that ageing alters how the body handles energy, nutrients, and waste. For both dogs and humans, this work shows that efficiency in using dietary protein diminishes with age and that this inefficiency can now be tracked through blood chemistry.
As proteins are broken down—either through normal tissue renewal or digestion—modified forms of amino acids appear in the blood. Normally, the kidneys filter these by-products out of circulation. The study shows that as kidney filtration becomes less efficient with age, these modified amino acids begin to accumulate. This accumulation does not cause ageing but serves as a measurable biomarker of it, helping scientists distinguish between a dog’s chronological age and its biological age.
This study highlights how closely linked protein use, nutrient use, and waste removal are. How efficiently a dog processes protein depends on genetics, age, and the quality of the protein in its diet. This becomes especially important when you look at how different types of pet foods are made.
Some commercial pet foods use rendered meat meals and added sodium or phosphorus to enhance flavour and extend shelf life. Studies in dogs show that too much dietary phosphorus can put extra strain on the kidneys, while excess sodium intake may affect kidney workload over time. High-temperature processing, such as extrusion or canning, can damage amino acid structure and reduce digestibility. Research on pet food processing shows that extrusion can trigger Maillard reactions, reducing the availability of essential amino acids like lysine and lowering overall protein digestibility. When proteins or additives are harder to digest, they generate more metabolic by-products—essentially, more waste for the kidneys to clear. These are the same types of metabolic waste products detected in the Dog Aging Project analysis.
By contrast, gently dehydrated, single-ingredient treats made from pure meat or seafood keep proteins closer to their natural state, with no additives, and result in less metabolic waste and easier kidney clearance. Veterinary research shows that higher-quality proteins produce fewer nitrogenous by-products (such as urea) and reduce metabolic strain on dogs’ kidneys. In everyday terms, the purer the protein and the fewer the additives, the easier it is for a dog’s ageing metabolism to function efficiently.
When choosing treats, it helps to think about how they interact with these processes. Short, recognisable ingredient lists reduce unnecessary compounds for the body to process. Named, single-source proteins, such as beef liver or king prawn, improve digestibility and nutrient quality. Avoiding artificial colours, preservatives, flavour enhancers, fillers, added sugars, and grain meals minimises metabolic burden and prevents excess by-product formation. Using human-grade ingredients means they are sourced and handled under stricter hygiene and traceability standards, reducing contamination risk and ensuring consistent quality. Gentle dehydration, rather than high-heat methods like extrusion or baking, preserves protein structure and nutrients, producing less waste during digestion.
The Dog Aging Project shows that ageing in dogs can be monitored through shifts in how the body builds and breaks down proteins—and kidney filtration, which clears waste from those processes. Until recently, scientists could not measure these changes in companion dogs at scale. Now they can, offering a clearer picture of what healthy ageing looks like on the inside. Choosing treats made with clean, single-ingredient proteins supports the body’s natural metabolic processes, and thoughtful feeding choices help your dog age well—from young adult to senior.