Bone cortical area in the evaluation of nutrition and activity levels

This study compares the differing impacts of nutrition and habitual activities on cortical area. While nutrition should have a systemic effect on cortical area, activities are more likely to result to localized changes in either cortical area, its distribution, or both. Two groups from the Southeastern United States were examined here: Archaic hunter-gatherers and Mississippian agriculturalists. Cross-sectional area and strength were greater in the femora alone of agricultural males. Agricultural females showed no increases in cortical area, but nonetheless had greater strength in both the arms and legs. In addition, in spite of significantly lower cortical area at one site-the proximal humerus-agricultural females maintained bone strength at this level. These findings suggest that most of the differences seen in cross-sectional area and structure are due to changing activities associated with the introduction of agriculture, although nutrition probably had a constraining effect on cortical area in agricultural females. Finally, in order to distinguish between the effects of diet and activities, it is best to examine more than a single bone and to consider both cortical area and its distribution, rather than area alone.