Safety of heavy metals as nutritional markers.

The nutritional safety of La, Sm, Eu, Tb, Dy, Tm, Yb, Sc and Cr oxides and barium sulfate were studied in two species. The mouse study was conducted for three generations, including reproduction. During the three generations the mice were apparently not effected by quantities of metals in the feed which were 1000 times the anticipated levels. This level of metals did not exhibit any effect on the reproduction or growth of the mice through three generations. It is concluded that the metals used in the diet of the mouse at any of the use levels could be used in diets for nutritional markers. The monkey study, in which 10 times the anticipated use level of heavy metal markers were fed, further illustrates the nutritional safety of the metals studied. The tissues analyzed generally illustrated that the metals were not detectable. The balance study indicated that all the metals could be accounted for and that there is no apparent absorption of these metals.