Olfactory self-selection of protein-containing foods.

When one unflavored, nonprotein diet was available in two differently scented bins, rats fed a protein-free diet over four days ate more from the bin smelling of gluten, ovalbumin, yeast or fibrin, but not soy, casein or lactalbumin, than from the bin smelling of butter. Rats fed a protein-containing diet over the same four-day period had no such preference. This result demonstrates that protein-deprived rats can use odor cues in making their selection of certain proteins. Since the direction, speed, and size of preference for these protein odors, excepting soy, are remarkably similar to those previously observed when rats actually consumed the proteins, olfactory stimuli appear to elicit appropriate protein selection responses independently of other protein quality variables such as taste, texture or nutrient composition.