Effects of different commercial diets on several orthopedic experiments

In experiments involving disuse osteoporosis induced by plaster cast immobilization, 2 commonly used commercial feeds (Wayne Lab Blox and Purina Laboratory Chow) gave different results. Preliminary evidence suggests that this dichotomy of results is due to an interaction between metabolic changes caused by physiologic stress and different levels of manganese in the 2 commercial diets. By feeding the 2 diets to groups of rats under various conditions, and examining the strength, cortical area, and length of their femurs, and by immobilization of a fracture in a cast, and associated physiologic stresses, dietary differences are manifested in the growth and developmental changes in the femur. Under normal, stress-free conditions, however, no such differences occur. Investigators should be wary of such dietary variables when comparing various experimental results. The implications of such effects insofar as human medicine is concerned should be further investigated.