Correlation between the physical properties of dietary fibers and their protective activity against amaranth toxicity in rats.

The mechanism(s) by which dietary fiber (DF) exerts beneficial effects on the growth of weanling rats fed toxic doses of amaranth (Food & C Red No. 2) was investigated. When crude DF (GDF) prepared from the roots of edible burdock (Arctium lappa L.) were added at graded levels to a purified basal diet supplemented with amaranth (control), growth was improved with increaseing GDF level up to and above that of the basal diet-fed group. The correlation equation obtained between the dietary percentage level of GDF (X) and the protective activity (Y) expressed as (difference in body weight gains between rats fed test and control diets) X 100/(difference in body weight gains between rats fed basal and control diets) was Y = 32.6 + 86.9 logX (r = 0.98). The comparative activities at the 5% level of various DF prepared from GDF decreased in the order of holocellulose, neutral-detergent fiber, GDF, crude fiber and acid-detergent fiber. Cellulose from cotton fiber had no activity. The activity was intimately related to their water-holding capacity (WHC) and settling volume in water (SV) (f = 0.90 and 0.96, respectively), but not to the capacity to bind amaranth. The correlation showed a saturation phenomenon quite similar to the equation described above in respect of GDF level. At the 10% level, even cellulose which has a low SV, showed protective activity similar to that of 3% GDF. From these and other results, it was concluded that the protective activity of various DF mainly depends on their physical properties such as SV or WHC.