Toxic growth response of rats fed a large amount of amaranth

The growth responses of rats were evaluated: (a) when they were intubated with a purified diet containing 4% amaranth (Food Red No. 2) with and without dietary fiber; (b) when fed a protein-free diet containing 5% amaranth with and without 7.5% dietary fiber; and (c) when fed the basal diet before and after feeding 5% amaranth. Dietary fibers were from gobo (GDF), edible burdock (Arctium lappa L.) and beet (BDF, Beta vulgaris L. var. rapa DUMORT.). Intubation of the 25% casein-sucrose basal diet containing 4% amaranth for 21 days resulted a lower body weight gain and lower food efficiency than the basal diet without amaranth despite the equal amount of nutrients (16g/day). However, the adverse effect of amaranth was counteracted by the concurrent intubation of 4% amaranth and 7.5% GDF. The feeding of 5% amaranth in a protein free diet also resulted a lower body weight than control rats fed the same diet without amaranth, and concurrent feeding of 7.5% BDF ameliorated the lowered body weight. When rats were refed the basal diet for 10 days after feeding 5% amaranth for 5 days, they showed a higher growth rate than with the same diet before amaranth feeding. These results suggest that dietary amaranth impairs not only the availability of ingested nutrients but also the reabsorption of endogenously secreted nutrients. However, the adverse effect of amaranth immediately disappeared when it was removed from the diet.