Grains fell out of favor following ultimately unproven associations among grain-free dog food and canine dilated cardiomyopathy (DCM). However, the DCM scare has faded, and consumers no longer face that pressure to believe that grains are bad, inherently. At the same time, the situation helped renew interest in the nutritional and physiological effects of grains in dog food. In this research, one repeating theme has emerged: not all grains are equal.
For example, Swedish University of Agricultural Sciences observed that metabolic responses in dogs may differ by type of grain.
“In dogs, whole rye or oats may not be favorable compared with whole wheat,” they wrote in research results published in the Journal of Animal Science.
The researchers compared the metabolic and hormonal effects of extruded dog foods containing whole grain rye, oats or wheat in healthy adult dogs. The study evaluated 18 healthy privately owned adult dogs in a crossover design. Each dog was fed one of three nutritionally complete extruded diets containing 25% whole grain rye, oats or wheat for four weeks before switching to another diet. Researchers collected blood and other samples over a four-hour period following feeding to measure glucose, insulin, glucagon-like peptide-1 (GLP-1), glucagon, triacylglycerol and cholesterol concentrations.
The researchers hypothesized that rye and oats would produce more favorable glucose and insulin responses than wheat because both grains have demonstrated those benefits in humans.
However, the three grain-based diets produced largely similar results, suggesting that rye and oats did not provide the metabolic advantages the researchers expected.
Dogs fed the oat-containing diet showed higher overall blood glucose, triglyceride and GLP-1 levels compared with dogs fed the wheat diet. While GLP-1 is involved in regulating metabolism and appetite, the higher GLP-1 response was accompanied by higher glucose and blood fat levels, making it difficult to view oats as a clear metabolic improvement over wheat, they wrote.
The rye diet produced the highest fasting insulin levels among the three diets. However, insulin responses after feeding were similar regardless of whether dogs consumed rye, oats or wheat.
Overall, the dogs' blood glucose, insulin, cholesterol and hormone responses followed similar patterns across all three diets. Wheat performed as well as, and in some cases better than, oats and rye in measures related to glucose and fat metabolism.
Although oats and rye are often associated with health benefits in people, those advantages were not evident in this study of healthy adult dogs.
