Healthy bone tissue “can be seen as a physiological hub of several stimuli of different origin (ie. dietary, endocrine, nervous, immune, skeletal muscle traction, biomechanical load).” Osteoporosis can develop with an imbalance in one or more of these aspects leading to a decrease in bone mineral density and bone mass and changing the structure and strength of bone tissue.
While osteoporosis and the risk of fracture or break can affect anyone, it commonly occurs with aging especially for post-menopausal women. Statistics from the International Osteoporosis Foundation, worldwide, indicate that “1 in 3 women over the age of 50 years and 1 in 5 men will experience osteoporotic fractures in their lifetime.”
Bone tissue is dynamic. It is constantly being reabsorbed and rebuilt. Peak bone mass, at about age 35, is “largely determined by genetic factors, health during growth, nutrition, endocrine status, gender, and physical activity.” As we age, the rate of bone resorption outpaces that of bone formation, leading to a loss of bone mass.
Primary osteoporosis occurs during the aging process. Secondary osteoporosis is defined as bone loss that results from clinical disorders. Addressing additional risk factors for primary osteoporosis – such as diet, hormone changes and lifestyle – is key to prevention or mitigation.
What is bone tissue?
“Bone consists of highly calcified, intercellular bone matrix, and three types of cells—osteocytes, osteoblasts, and osteoclasts. The outer surface of bone is covered by periosteum, which is bound to bone by bundles of collagen fibers known as Sharpey's fibers, and the inner bone surface is lined with endosteum.”
65% of bone tissue is inorganic mineral, largely calcium and phosphorus in the form of an insoluble salt called hydroxyapatite: “Hydroxyapatite crystals lie adjacent and bound to the organic protein matrix. Magnesium, sodium, potassium, and citrate ions are also present, conjugated to crystals rather than forming distinct crystals of their own.”
The remaining 35% of bone tissue is an organic protein matrix that consists mainly of type I collagen plus non-collagenous matrix proteins, proteoglycans.
Factors impacting mineral and bone density in primary osteoporosis include changes in hormones: “Post-menopausal osteoporosis is caused by increased activity of osteoclasts, related to decreased levels of estrogen in the circulation. Lack of estrogen is associated with an increased release of cytokines, such as interleukin (IL)-1 and IL-6, which stimulate osteoclasts.”
Additional risk factors for osteoporosis include diet (calcium and vitamin D especially) and lifestyle choices such as smoking, heavy alcohol consumption and physical inactivity. Research indicates that regular exercise “stimulates bone metabolism and bone formation in part through muscle traction onto the bone, stress triggering the endocrine system and homeostatic adaptation.”