Researchers in the UK tested 31 different dry dog foods to see if plant-based options are as nutritious as meat-based ones. They found that plant-based dog foods can be just as complete and healthy as meat-based foods for most nutrients. However, plant-based foods had lower levels of iodine and B-vitamins, which are easy to add as supplements. The study also found that some special veterinary diets designed for kidney health were missing important amino acids (building blocks of protein). This research helps dog owners understand whether switching their pets to plant-based food is a healthy choice.

The Quick Take

  • What they studied: Whether plant-based dog foods have the same nutrition as meat-based dog foods, and if they meet official nutrition guidelines for dogs.
  • Who participated: 31 different commercial dry dog foods sold in the UK: 19 regular meat-based foods, 6 special veterinary foods (for sick dogs), and 6 plant-based foods. The foods themselves were the subjects, not actual dogs.
  • Key finding: Plant-based and meat-based dog foods are nutritionally similar for most nutrients. However, plant-based foods had noticeably lower iodine and B-vitamins. About 66% of special veterinary diets were missing some essential amino acids they should contain.
  • What it means for you: If you want to feed your dog a plant-based diet, it can work well—but you should add iodine and B-vitamin supplements. Talk to your veterinarian before making the switch. Special veterinary diets may need extra attention to ensure they’re complete.

The Research Details

Scientists bought 31 different complete dry dog foods available in UK stores and sent them to a laboratory for detailed testing. They measured 31 meat-based foods (including 6 special veterinary diets) and 6 plant-based foods. Each food was tested for protein content, individual amino acids (the building blocks of protein), different types of fats, minerals like calcium and iron, vitamin D, and all the B-vitamins. The researchers then compared what they found to official nutrition guidelines for dog food to see which foods met the standards.

This approach is straightforward and practical because it directly tests real foods that people actually buy for their dogs. By comparing plant-based and meat-based options side-by-side, the researchers could identify specific nutritional differences. The study focused on ‘complete’ foods, meaning foods labeled as having all nutrients dogs need.

This research matters because more dog owners want to feed their pets plant-based diets for ethical or environmental reasons. Before this study, there wasn’t much scientific information comparing the actual nutrition in these foods. By testing real commercial products, the researchers provided practical information that dog owners and veterinarians can use to make informed decisions. Understanding which nutrients might be missing helps owners know what supplements their dogs might need.

This study has some strengths: it tested real commercial foods that people actually buy, it measured many different nutrients comprehensively, and it compared results to official guidelines. However, the study only looked at the food itself, not how dogs actually digest and use these nutrients. The sample size of plant-based foods (only 6) is relatively small, so the findings might not represent all plant-based options. The study was published in PLoS ONE, a reputable peer-reviewed journal, which adds credibility.

What the Results Show

When researchers compared plant-based and meat-based dog foods, they found them to be surprisingly similar in most nutrients. Both types of food generally contained adequate protein, fats, and most minerals and vitamins. However, plant-based foods consistently had lower levels of iodine (a mineral important for thyroid health) and B-vitamins (important for energy and nerve function). Specifically, only 16% of all tested foods met the guidelines for B-vitamins, suggesting this is a widespread issue across both food types.

The study found that 100% of foods tested met vitamin D guidelines, which is good news. However, only 55% of foods met guidelines for all essential amino acids (the specific protein building blocks dogs need). This means nearly half of the foods tested were missing at least one essential amino acid.

Special veterinary diets designed for dogs with kidney disease were particularly concerning. These diets are intentionally made with lower protein, but the researchers found that 66% of them were missing one or more essential amino acids. This suggests that while these diets successfully reduce protein, they may not be balancing the remaining protein properly.

The study found scattered instances where individual foods didn’t meet guidelines across all food groups. Some meat-based foods also had nutritional gaps, showing that being meat-based doesn’t automatically guarantee complete nutrition. The research highlighted that mineral content (like calcium, phosphorus, and trace minerals) was generally adequate across most foods. However, the B-vitamin deficiency appeared across all three food categories, suggesting this is a manufacturing or formulation issue rather than a problem specific to plant-based foods.

This is one of the first comprehensive studies directly comparing plant-based and meat-based commercial dog foods in terms of actual nutrient content. Previous research suggested that plant-based diets for dogs might have nutritional gaps, but this study provides specific data showing which nutrients are actually problematic. The findings align with general nutrition science showing that plant-based diets often contain lower B-vitamins and iodine compared to animal-based foods. However, this study shows that with proper supplementation, plant-based dog foods can be nutritionally adequate.

The study only tested 6 plant-based foods, which is a small sample that may not represent all plant-based options available. The research analyzed the food composition but didn’t test how well dogs actually digest and absorb these nutrients—some nutrients might be more or less available depending on how they’re processed. The study only included foods from the UK market, so results might differ in other countries. Additionally, the study didn’t follow actual dogs over time to see if they stayed healthy on these diets, which would provide real-world evidence of nutritional adequacy.

The Bottom Line

If you want to feed your dog a plant-based diet, current evidence suggests it can be nutritionally adequate with careful attention to supplementation. You should: (1) Choose a plant-based dog food labeled as ‘complete and balanced,’ (2) Add iodine and B-vitamin supplements as recommended by your veterinarian, (3) Have your veterinarian monitor your dog’s health regularly with blood tests to ensure proper nutrition. If your dog has kidney disease or other health conditions requiring a special veterinary diet, discuss plant-based options carefully with your vet, as these diets may have amino acid imbalances. Confidence level: Moderate—this is based on one study of commercial foods, not long-term health outcomes in dogs.

This research is most relevant for dog owners who want to feed their pets plant-based diets for ethical, environmental, or personal reasons. Veterinarians should be aware of these findings when advising clients about plant-based options. Owners of dogs with kidney disease or other conditions requiring special diets should pay particular attention to the findings about veterinary diets. Dog food manufacturers should use this information to improve their formulations. Dog owners feeding standard meat-based diets should also be aware that some commercial foods may have nutritional gaps, so choosing reputable brands and regular veterinary check-ups remain important.

If you switch your dog to a plant-based diet with proper supplementation, you won’t see immediate changes. Dogs typically need 4-8 weeks to fully adjust to a new diet. Health benefits or problems from nutritional deficiencies typically develop over months to years, not days or weeks. This is why regular veterinary check-ups (at least annually, more frequently for older dogs) are important to catch any nutritional issues early.

Want to Apply This Research?

  • Track your dog’s food brand, type (plant-based or meat-based), and any supplements given daily. Note the date you switched foods and monitor your dog’s weight, coat condition, and energy level weekly. Record any changes in digestion, appetite, or behavior.
  • If using a nutrition app, log your dog’s current food and supplements. Set a reminder to discuss plant-based diet options with your veterinarian. Create a checklist of supplements (iodine, B-vitamins) to ensure you’re giving them consistently. Schedule quarterly veterinary check-ups to monitor your dog’s health on a new diet.
  • Use the app to track your dog’s weight monthly and note any changes in coat quality, energy level, or digestion. Set reminders for supplement administration to ensure consistency. Keep records of veterinary visits and any blood test results. Compare notes over 3-6 months to identify any patterns that might indicate nutritional issues. Share this data with your veterinarian at check-ups.

This research analyzes the nutritional content of commercial dog foods but does not provide medical advice for your individual dog. Before switching your dog to a plant-based diet or making any significant dietary changes, consult with your veterinarian. Dogs have individual nutritional needs based on age, size, activity level, and health status. Your veterinarian can recommend appropriate foods and supplements for your specific dog. If your dog has existing health conditions, allergies, or is taking medications, dietary changes require professional veterinary guidance. This study should not replace personalized veterinary nutritional advice.