Without hard framework nothing can organize. Without poles the building has no supporter and is easy to ruin. Without bone all vertebrates have no skeleton and cannot move or shift to anywhere. Bone is the main part of the body that makes up the hard framework for whole physical structure of vertebral animals.

As a living tissue, bone is unique in that it is not only rigid and resists forces that would ordinarily break brittle materials but is also light enough to be moved by coordinated muscle contractions (1, 40, 41). These characteristics are functions of the strategic locations of two major types of bone. Cortical bone composed of densely packed mineralized collagen laid down in layers, provides rigidity and is the major component of tubular bones (1, 2). Trabecular (cancellous) bone is spongy in appearance, which provides strength and elasticity, and constitutes the major portion of the axial skeleton (1, 2). Disorders in which cortical bone is defective or scanty lead to vertebral fractures. Fractures of long bones also may occur because normal trabecular bone reinforcement is lacking (1).

Two-thirds of the weight of bone is due to mineral and the remainder to water and collagen (1). Minor organic components, such as proteoglycans, lipids, noncollagenous proteins, and acidic proteins containing g-carboxyglutamic acid are found (1). The mineral of bone is present in two forms. The major form consists of hydroxyapatite in crystal of various maturity (1). The remainder is amorphous calcium phosphate (1). This form has a lower calcium-to-phosphate ratio than pure hydroxyapatite occurs in region of active bone formation and is present in large quantities in young bone.

Bone is resorbed and formed continuously throughout life. There are three types of bone cell involved in bone formation and resorption cycle. Osteoblasts form new bone on surfaces of bone previously resorbed by Osteoclasts (1, 2, 46). The osteoblasts are thought to be derived from a population of dividing cells on bone surfaces that arise from mesenchymal cells in bone connective tissue. Osteoblasts are actively involved in the synthesis of matrix components of bone (primary collagen) and probably facilitate the movement of mineral ions between extracellular fluid and bone surfaces. The physiologic importance of such ion transport by osteoblasts, if it occurs at all, is controversial, but there is widespread agreement that osteoblast-mediated transport of calcium and phosphorus is involved in mineralization of collagen, which in turn is crucial to the formation of bone. In the present of bone formation, osteoblasts gradually become encased in the bone matrix that they have produced. Once osteoblasts are trapped in the mineralized matrix, their functional and morphologic characteristics change and they are then called Osteocytes (1, 2, 46). Protein synthetic activity decreases markedly and the cells develop multiple processes that reach out through lacunae in bone tissue to “communicate” with processes of other osteocytes within a unit of bone (osteon) and also with the cell processes of surface osteoblasts. Osteocytes are believed to act as a cellular syncytium that permits translocation of mineral in and out of regions of bone removed from surfaces (1, 46). The osteoclast is a multinucleated giant cell that is responsible for bone resorption (1, 2, 46). It is probably derived from circulating mononucleated macrophages, which differentiate into the mature osteoclasts by fusion in the bone environment. These cells can secrete the enzymatic components that are able to solubilize matrix and releasing calcium and phosphorus. When the mineral is released, it is transported through the osteoclast into the extracellular fluid and ultimately into blood.

Normally there is a balance of bone resorption and formation, but when we are getting old, bone resorption rate becomes higher than bone formation rate. That’s why elder always has problem with bone. They have risk to get broken bone and bone diseases.

Osteoporosis: is a disease characterized by an absolute decrease in bone mass that results in an increased susceptibility to fracture easily at the wrist, spine, and hip (1, 2, 20). It is common in postmenopausal women and in elderly persons of both sexes and constitutes an important public health problem (1, 20, 34, 35, 38, 40, 41, 46, 48). The level of bone mass achieved at skeletal maturity (peak or maximal bone mass) is one major factor modifying the risk of development of osteoporosis (1). The more bone mass that is available before the period of age-related bone loss, the less likely it will decrease to a level at which fracture will occur. In the United States alone, more than 1 million fractures occur each year at a cost of more than $13.8 billion (20). Moreover, the number of hip fracture in the United States is projected to triple between 1990-2040 (20). Although women have a markedly higher risk of developing this disease (48), approximately 3-6% of men over the age of 50 have osteoporosis and 28-47% have osteopenia (17, 20), the condition characterized by lower density of bone mass because of lower synthesis of bone tissue (2). To date, there are no known therapeutic interventions that can restore bone mass to normal once the bone matrix has been lost. Because bone loss is largely an irreversible process, it is essential to maintain existing bone mass. Several dietary approaches have been examine in relation to their ability to influence bone mass. The majority of dietary interventions have focused on calcium intake because calcium is the main mineral in bone and insufficient intake of this mineral causes bone resorption to compensate the inadequate calcium in the body (1, 14, 15, 20, 22, 24, 26, 27, 29-34, 40, 41-44, 46, 47)).

Vitamin D is essential for maintaining the mineral balance in the body. It aids in the absorption and utilization of calcium and phosphorus (1, 20, 42, 43, 45). They are two minerals essential for healthy development of bones and teeth. The sufficient vitamin D is also influential in the maintenance of bone mass.

Not only postmenopausal women and old people that have risk to loss bone mass, but also persons with some conditions such as pregnant & lactating women, bone degeneration diseases, etc.

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