Glycemic and insulinemic responses after Ingestion of commercial foods in healthy dogs: influence of food composition

Great variations in the postprandial glucose concentration and insulin secretory responses to different foods have been shown in dogs (Holste and al. 1989, Nguyen and al. 1994). It has been suggested that foods yielding low glycemic responses would be recommended for diabetic or obese subjects and in the prevention of many other disorders. High carbohydrate/high fiber diets enhance peripheral glucose disposal and decrease insulin requirements in insulin-dependent diabetic subjects. In overweight patients with noninsulin-dependent diabetes mellitus (NIDDM),4 reducing diet glycemic response improves overall blood glucose control, long-term glycemic control and lipid control. Diets with a high glycemic response that are low in fiber increase the risk of NIDDM in humans. Foods with a low glycemic response combined with a high dietary fiber content decrease free fatty acid level, which is associated with abdominal obesity and cardiovascular risk. They cause rapid intestinal absorption of glucose into the blood, leading to postprandial hyperinsulinemia, which may play a role in promoting colon carcinogenesis. A diet high in refined carbohydrates and low in water-soluble fiber causes rapid absorption of glucose with similar results.

Because of the clinical implications of the glycemic index, notably in diabetes management or in dietary strategy to avoid or treat overweight or moderate obesity, the factors that affect it have been the subject of many studies (Wolever and al. 1991).

The extent of postprandial hyperglycemia and insulin secretion depends on the amount of food and carbohydrate consumed per meal. However, different kinds of carbohydrate elicit different glucose and insulin concentrations, because their chemical nature, especially the ratio of amylose to amylopectin forms of starch, may affect their rate and speed of digestion. Dietary fiber slows down the rate of passage and the rate of hydrolysis of starchy polysaccharides (Wolever 1990). Dietary fat delays stomach emptying (Gulliford and al. 1989), and high intakes of rapidly digested proteins modify the glycemic response by increasing insulin secretion (Nuttall and Gannon 1990). The food processing may be of particular importance for dog food. The type of food, dry, canned or soft moist, affects the maximal postprandial glucose concentration as much as the time at which this peak occurs (Holste and al. 1989).

The glycemic index methodology is based on tests of single foods and could be applied to the testing of mixed meals. Nevertheless, its practical utility is controversial because differences among foods could be partially abolished in mixed meals by the effects of protein and fat. Whatever it may be, an individual food evaluation is not realistic in dogs. Their complete foods contain many components. There are large variations in their protein and fat content and the technological processes can largely modify the intrinsic carbohydrate availability.

Nevertheless, information concerning postprandial responses would be of great interest in regard to obesity. Along with a long-term excessive energy intake, food quality may play a significant role according to its humoral and metabolic effects. This information may also be of interest in the management of NIDDM (which elicits alteration of carbohydrate tolerance and insulin action) as much as insulin-dependent diabetes mellitus (IDDM; reduction of fluctuations in blood glucose, synchronization of glucose increase and insulin administration).

The purpose of this study was to determine how the differences in carbohydrate (starch and dietary fiber, soluble and insoluble), protein and fat content of complete (and complex) foods given to healthy dogs in a single meal on a normoenergetic basis modify their postprandial plasma glucose and insulin responses.