Grain-free diets re-visited: an update on pulses in pet food

Pet foods marketed as ‘grain-free’ primarily use pulses, protein-rich seeds such as peas, lentils, chickpeas, and various types of beans found in legume crops. While they began as a popular and healthy alternative to grain-based pet foods, pulses quickly fell under scrutiny following a 2018 FDA investigation on grain-free diets and their potential role in canine dilated cardiomyopathy (DCM). However, this 2022 investigation concluded no causal link exists between grain-free diets and DCM currently.

New research sheds further light on safety

Amidst the controversy, a 2023 study conducted at the Ontario Veterinary College has brought fresh insights into the use of pulses in grain-free pet food formulations, helping re-establish a prospective future for pulses. To date, this is the longest controlled feeding study to assess the safety of pulse-based diets in healthy adult dogs.

The main focus of the study was to monitor the effect of increasing dietary pulse concentrations (primarily peas) on cardiac function, plasma sulfur amino acid (SAA) concentrations, body condition, and blood values over a 20-week dietary trial. Test diets contained between 0%-45% pulse ingredients, reflecting concentrations in commercial diets that meet and/or exceed guidelines from The Association of American Feed Control Officials (AAFCO).

Their data addresses 3 main concerns associated with grain-free diets.

1. Cardiac function

The study found no negative impact on cardiac function among the different dietary treatments after 20 weeks. Even at 45% pulse inclusion, there were no changes to cardiac function (assessed using echocardiography) or to concentrations of biomarkers commonly associated with cardiomyopathy (NT-proBNP and cTnI).

2. Sulfur Amino Acid (SAA) status

Taurine is a non-essential amino acid required for cardiac function and is synthesized from sulfur-containing amino acids like methionine and cysteine. Despite pulses being generally low in SAA, pulse-containing diets did not cause deficiencies in plasma SAA concentrations when fed a complete and balanced diet with 45% pulse inclusion. This means that pulses did not interfere with the absorptive processes of the intestines, since adequate levels of SAA were maintained in the serum and available for taurine synthesis.

3. General safety and efficacy

The study concludes that balanced and complete diets containing pulses, specifically peas, were safe for healthy adult dogs over a 20-week study period. No adverse effects on body condition, blood values, and biochemical changes occurred among the different dietary treatments.

Overall, the results of this study suggest that dog foods containing pulses are not a causative factor for DCM in non-genetically predisposed dogs. It should be noted though, that this study is relatively small, using only 28 dogs – 7 in each dietary group – and should be interpreted accordingly.

The value of peas

Peas are the second most valuable legume (after soybean), with a rich nutrient profile high in proteins and carbohydrates while remaining low in fats. They are particularly abundant in potassium, B vitamins, and essential amino acids. However, pea protein must be supplemented with SAAs to formulate a complete and balanced diet.

As pet ownership continues to grow exponentially, the need for sustainable and high-quality ingredients has become a priority. Recent animal and grain production shortages have presented challenges, sparking the search for scalable solutions.

Pea production emerges as a promising answer to sustainability. With high yields per acre, reduced water consumption, and nitrogen-fixing capabilities, peas are not only eco-conscious, but also a cost-effective option for pet food formulations.

Future applications

The FDA’s inconclusive findings on grain-free diets and the safety demonstrated by recent controlled food trials pave the way for innovative applications of pulses (and more specifically pea protein) in pet food. Some examples include:

Diet sensitivities

Nearly 30% of veterinary visits result from vomiting and diarrhea. Dietary elimination trials are commonly used both in diagnosis and management of gastrointestinal disorders. Current hypoallergenic diets often rely on hydrolyzed or novel protein sources. Pea protein has the potential to be incorporated into hypoallergenic diets as an additional tool to help manage food sensitivities and avoid common dietary allergens.

Encapsulation techniques for bioactive ingredients

Bioactive compounds are secondary metabolites found in whole foods that are difficult to preserve due to pH sensitivity, UV exposure, and thermal processing used in extrusion. This limits their use in pet food products unless they are preserved and encapsulated.

The main techniques include spray-drying, emulsion, and complex formation to stabilize lipophilic bioactive ingredients like β-tocopherol, omega-3 fatty acids, and linolenic acid to incorporate them into pet food formulations. Encapsulation has also helped deliver water-soluble vitamins to the intestines for absorption. For example, pea protein microparticles cross-linked with transglutaminase have been used to encapsulate riboflavin (vitamin B2), with 74% to 84% successfully reaching the gastric and intestinal fluids.

Food emulsification

Pea protein can stabilize liquid emulsions and microencapsulate oils to enhance the texture and palatability of pet food. Under the right conditions, pea protein can reduce the surface tension between oil and water, helping form stable emulsions that enhance the overall sensory experience for pets. A recent Agriculture and Agri-Food Canada study shows that pea protein even outperforms soy as an emulsifying agent at a neutral pH.

Moving forward

Pea protein has emerged as a sought-after ingredient in the food industry, driven by its versatile applications, low cost, and nutritional benefits.

As consumer demand for sustainable and allergen-free options continues to grow, pea protein offers
a promising solution for the future of pet food formulations. With new studies addressing safety concerns, pulses show great potential to shape the pet food industry.