HE-150
Osteoporosis:
What You Should Know
April C. Mason
Foods and Nutrition Extension Specialist
Introduction
Osteoporosis is an age-related bone disorder that is characterized by decreased bone mass and increased susceptibility to bone fractures. The disorder affects 15-20 million persons in the United States alone, and the medical costs incurred for treatment, rehabilitation, and care of osteoporosis patients is over $3.8 billion dollars annually. This publication discusses topics of possible causes of the disorder, how it can be treated, and most importantly, how it can be prevented.
Causes of Osteoporosis
Much research is currently being done to determine the causes of osteoporosis. A complete understanding of the disorder is not yet available. At this time, a combination of factors are thought to be responsible for osteoporosis. These factors are:
•	inadequate calcium in the diet
•	deficiency of estrogen hormone
• lack of exercise.
Composition of Adult Bone
To understand how these factors affect bone, bone mass, and calcium balance in the body, one needs to understand bone anatomy and the function of calcium in the body.
It is a general misconception that bone develops during youth and then is static or unchanging for the rest of the life cycle. Bone is constantly changing no matter what a person’s age. Bone is made up of water, minerals, protein, and fat. There are two cell types in bone: one active in bone building (osteoblasts) and one active in bone destruction (osteoclasts). There are even veins and arteries in bone tissue supplying it with blood carrying necessary nutrients.

Bone building and bone destroying are both occurring constantly throughout life. The
• marvel of normal physiology is that these two opposite processes are held in balance.
Osteoporosis is a state of imbalance with more bone being destroyed than is built over a long period of time.

Calcium Balance
The maintenance of calcium balance and bone health in our bodies is complex. Various mechanisms are involved. There are two pools of calcium in the body: 99% of body calcium is stored in the bone and teeth, while 1% of body calcium is in the blood and soft tissues.
Figure 1. Calcium balance. The maintenance of calcium levels between the blood and the rest of the body is critical for health.
While bone is necessary for structure, protection, and support of our bodies, it also acts as a calcium reservoir or reserve. The pool of calcium in bone is flexible and changes to some small extent throughout life.

The calcium in blood and soft tissues, although only 1% of our total calcium, is absolutely essential for life. The concentration of calcium in blood cannot vary without severe
Purdue University Cooperative Extension Service • West Lafayette, Indiana