DURATION OF DIETARY RESTRICTION - AN IMPORTANT DETERMINANT FOR THE INCIDENCE AND AGE-OF-ONSET OF LEUKEMIA IN MALE F344 RATS

The effect of duration and age of initiation of dietary restriction (DR) on the spontaneous occurrence of leukemia was studied in male F344 rats. Four nutritional paradigms were employed: Group I, ad libitum fed; Group 2, dietary restricted starting at 6 weeks of age; Group 3, dietary restricted from 6 weeks to 6 months of age; Group 4, dietary restricted starting al 6 months of age. The relative incidence (relative onset rate) of leukemia,vas highest in the rats of Groups 1 and 3 and lowest in the rats of Group 2. The age of onset was earliest in Group 1 followed by Groups 3, 4, and 2 in that order. The progression (duration from onset to death) did not differ significantly between the groups. These results indicate that the duration of DR correlates with the incidence and age of onset of leukemia but not with its progression. The age of initiation of DR is not as important a determinant as the duration of DR in regard to incidence and age of onset. The incidence and the age of onset of leukemia appear to rt late to the total cumulative energy intake of the rat (i.e., age multiplied fly mean daily energy intake).