Osteoporosis in Biocultural Perspective

Osteoporosis is a condition in which loss of bone density leads to increased risk of fracture. This condition is increasing in frequency in most parts of the world and has become a major cause of medical expenditures in the United States, where it is estimated to cost nearly $10 billion per year. European countries report similar increases in the proportion of their medical costs attributable to osteoporosis. In most cases, osteoporosis, which occurs earlier and more frequently in women, is associated with age-related endocrine changes, especially the decline in estrogen production occurring at menopause. However, earlier occurrence resulting from factors such as inactivity, low bone peak density in early adulthood, low calcium intake, and a variety of dietary and lifestyle factors can lead to high risk of fracture before menopause. This is because bone is in a continual state of turnover, and the balance between bone formation and resorption can be upset by a number of endogenous and exogenous factors. Relatively inefficient intestinal absorption of calcium, which can increase the risk of osteoporosis, is probably an adaptation that avoids the necessity of excessive kidney excretion of calcium. Modern lifestyles and increased life expectancies are exposing the biological cost of this adaptation.