Are Food Preference Tests with Laboratory Rats a Proper Method for Evaluating Nutritional Quality?

Abstract

As an addition to analytical methods, food preference tests represent a new approach in the investigation of food quality. This method was put to a test with common beets from biological and conventional farming systems and with different kinds of bread containing improving or debasing substances (milk thistle, ground sunflower seeds, ergot, undigestible roughages) and different proportions of wheat and rye. Laboratory rats were used as test animals because of their versatile feeding behaviour: rather than restricting themselves to one known food, they will sample every food offered to gather experience and to form optimal feeding habits. For this trial two groups of animals were used: one consisting of rats fed with biologically cultivated products (group A) and one fed with conventionally cultivated products (group B). Animals of both groups significantly preferred biologically grown common beets, but rats of group A exhibited a higher sensitivity in their choice of food. The preference tests with bread demonstrated that wheat was preferred to rye, ergot was avoided, bread to which fat has been added was preferred, and a greater amount of the bread with roughages was ingested to maintain the energy balance. These experiments showed that two fundamental influences on the food choice must be taken into account: —the short term effect, which prompts rats to prefer food of softer consistency, with more processed ingredients and of higher fat content. —the long term effect, which, after the physiological effect of the food has been experienced, increasingly influences rat feeding behaviour. Physiological needs come to determine the choice or avoidance of food.