Study: A Dog’s Diet Has Greater Environmental Impact Than a Human’s

Introduction

When we talk about lowering the environmental footprint of what we eat, the conversation almost always centers on human diets. Yet a growing body of evidence suggests that the kibble in Fido’s bowl may carry a heavier ecological burden than the food on our own plates. A new peer-reviewed study published in the journal Animals is the first to quantify this disparity on a global scale—and the numbers are striking.

Understanding the Research

Veterinary Professor Andrew Knight of the University of Winchester analysed 2018 data on global pet populations, ingredient lists of best-selling dog foods, and United Nations FAO statistics on meat production. By converting ingredient proportions into “farmed land animal equivalents,” Knight calculated how many chickens, pigs, turkeys and other terrestrial livestock are ultimately required to feed the planet’s estimated 900 million dogs.

Why dogs?

Dogs are the most numerous large companion animal, their numbers are rising faster than human population growth, and commercial dog foods typically rely heavily on animal by-products that still drive demand for livestock farming. In contrast, cat diets contain smaller total volumes of meat and were therefore excluded from the headline comparison.

Key Findings

• 40 % higher toll: The average dog’s diet consumes roughly 13 farmed land animals per year, compared with nine for the average person.
• Calorie source: On average 34 % of metabolisable energy in dog food comes from animal ingredients versus 19 % in human diets.
• Country variation: In the United States, a person still eats more animals (24) than a dog (20), but the gap narrows to about 20 %.
• Scale of opportunity: If every dog in the world transitioned to a nutritionally complete plant-based diet, six billion land animals would be spared annually—more than the combined population of cattle, pigs, sheep and chickens raised in the United States and EU.
• Climate payoff: The associated drop in greenhouse-gas emissions would equal 1.5 times the entire UK’s annual footprint.
• Food security bonus: The calories no longer fed to livestock could feed 450 million people, roughly the entire population of the European Union.

Methodology in Brief

Knight used a “top-down” life-cycle approach. He first estimated total global dog numbers by extrapolating pet ownership surveys across six continental regions. Next he parsed ingredient declarations of 280 dry and wet foods that together account for >60 % of international sales. Each ingredient was assigned a “livestock conversion factor” derived from FAO feed-to-meat ratios. For instance, producing 1 kg of poultry meat requires 1.8 kg of feed, so every kilogram of chicken meal in dog food was multiplied accordingly. Finally, he aggregated national consumption statistics to arrive at per-dog and per-person animal totals.

Implications for Sustainability

Overlooked leverage point

Pet food is rarely discussed in climate policy circles. Knight points out that fewer than two full-time academic researchers outside industry currently study sustainable pet diets, and less than 1 % of the farmed-animal advocacy movement’s budget targets this area. In effective-altruism terms, the field scores high on “neglectedness,” making it a potentially high-impact intervention.

Alternative proteins already exist

Plant-based dog foods supplemented with taurine, L-carnitine, vitamin B12 and other nutrients have been on the market since 2005. By early 2026, 14 peer-reviewed studies and one systematic review indicate that dogs maintained on properly formulated vegan diets show comparable health outcomes to those on meat-based kibble. Microbial proteins (produced via fermentation) and cultivated meat grown in bioreactors are also entering the pet-food pipeline, offering additional pathways to cut impacts.

What This Means for Pet Owners

Check the label

Not all vegan dog foods are equal. Look for products that meet Association of American Feed Control Officials (AAFCO) or European FEDIAF nutrient profiles for adult dogs or all life stages, and that undergo feeding trials or laboratory analysis.

Transition gradually

Introduce new foods over 7–10 days by mixing increasing proportions with the old diet to avoid gastrointestinal upset.

Monitor health markers

Schedule annual blood work to check albumin, B12, folate and electrolyte levels, especially during the first year after switching.

Policy and Industry Outlook

Some governments already incentivize low-carbon pet food. The Netherlands lowered VAT on plant-based pet food from 21 % to 9 % in 2021, recognizing its climate benefits. Expect similar measures elsewhere as national carbon budgets tighten. Meanwhile, major retailers are expanding shelf space for “eco” or “vegan” pet ranges. Mars Petcare recently invested in a research hub for cultivated meat pet products, signalling industry buy-in.

Limitations and Future Research

Knight’s study relies on 2018 data; dog populations have grown since, particularly in Asia. Regional variation in feeding practices (e.g., home-made versus commercial) introduces uncertainty, and marine animals such as fish were excluded. Future work should incorporate updated census data, fishmeal impacts, and consumer willingness-to-pay surveys for alternative-protein pet foods.

Conclusion

The environmental paw-print of our canine companions is larger than many environmentalists realised. Fortunately, the solution is already in aisle five: nutritionally balanced plant-based dog foods that satisfy palatability, health, and sustainability criteria. Swapping an average dog to a vegan diet for a single year spares more farmed animals than eliminating all meat from a human diet over the same period. For policymakers, advocates, and everyday pet owners, that represents an embarrassingly underused opportunity to curb greenhouse-gas emissions, conserve biodiversity, and improve global food security—one bowl at a time.

References

Knight, A. (2026). The Relative Benefits of Plant-Based Diets for Dogs and Humans. Animals, 16(3), 460. https://www.mdpi.com/2076-2615/16/3/460