Osteoporosis is a disease in which low bone mass leads to an increased chance of developing fractures. It is an end-stage condition, caused by a chronic disruption of skeletal homeostasis. When faced with a severe dietary shortage of calcium, the body pulls this mineral from the bones to maintain levels needed in the blood. This causes loss of bone density and strength. Bones fracture more easily; an advanced osteoporotic fracture can happen when the person is sitting down.
The consequences of osteoporosis can cause pain, loss of activity and restricted movement. However, the bone loss that precedes the osteoporotic fracture is a symptomless process, so osteoporosis may go undetected until bones become so brittle that even the slightest trauma causes a fracture, with fractures of the hip, wrist and spine being the most common. The spine is the most common region of fracture, with one third of women 65 years and older having sustained spinal vertebrae fractures, leading to loss of height, kyphosis (dowager's hump), and chronic back pain. By extreme old age, one of every three women and one of every six men will have a hip fracture which, by any measure, is the most devastating of all osteoporotic fractures.
Significant contributors to this degenerative process include nutritional, endocrine, physical, lifestyle, genetic and environmental factors. Some of the risk factors include: inadequate nutritional intake, lack of physical activity, smoking, excessive alcohol consumption and prolonged use of corticosteroids. The current medical treatment mainstay, hormone replacement therapy, slows bone loss and reduces fracture incidence, but must be taken for ten or more years to realize this benefit. Unfortunately, this approach subjects women to a long-term therapy that poses significant concern due to increased risk of breast cancer, uterine cancer and side effects.
Two major factors that influence the risk of development of osteoporosis are the level of bone mass achieved at skeletal maturity (peak bone mass) and the rate at which bone loss occurs in later years. The more bone mass available before age-related bone loss ensues, the less likely it will decrease to a level at which fractures occur. The best way to prevent osteoporosis is to build strong bones during childhood and adolescence.
The major risk factors of osteoporosis in women are (1) Family history of osteoporosis; (2) Caucasian or Asian; (3) Small body frame; (4) Postmenopausal; (5) Hysterectomy; (6) Inadequate calcium intake; (7) Excess protein in the diet; (8) Inadequate exercise; (9) Smoking; (10) Excessive alcohol consumption; (11) High caffeine intake; (12) Long-term glucocorticoid therapy; (13) Long-term use of anticonvulsants or antacids; (14) Hyperparathyroidism; (15) Thyrotoxicosis; (16) Cushing's syndrome; (17) and type 1 diabetes.
In addition to diet and lifestyle factors, genetic and ethnic factors significantly influence many aspects of calcium and skeletal metabolism. Caucasian and Asian women tend to have lower bone density than African and Hispanic women and consequently, are more likely to suffer from osteoporotic fractures. The same holds true for thin, smaller boned women. Evidence also suggests there may be a link between mother and daughter; mothers with low bone mineral content. Whether this link is a function of heredity or the influence of the mother's habits, or both, remains uncertain. What does appear certain is that regular exercise, lifetime maintenance of an adequate nutritional status with regard to calcium and other nutrients important for bone health, and a healthy lifestyle are essential for maximizing peak bone mass for minimizing the rate of bone loss that occurs with aging, and thus reducing the risk of osteoporosis.
There are numerous countries that have a very low rate of osteoporosis despite the fact that the people consume as little as 200 mg of calcium a day, considerably less than the 1,000 to 1,500 mg of calcium that most doctors recommend for pre- and post-menopausal women. This points to another aspect of the problem of osteoporosis, that consumption of certain foods in excess can that leach calcium out of their bones. In certain cultures, this risk factor may dominate over others. Despite the fact that Eskimo women get over 2,000 mg of calcium a day (from their consumption of fish bones), and even though exercise is a regular part of their life, they are known to have one of the highest rates of osteoporosis in the world. This problem is not due to bad luck. It is because they eat so much protein (as much as 250 to 400 grams a day) and so much fat. This diet hinders calcium absorption.
Osteoporosis is the most common metabolic bone disease. It is most common in postmenopausal women, but can affect both men and women of any age. In 1991 it was estimated that osteoporosis affected over 20-25 million Americans and is projected to cost $30-40 billion dollars annually by the turn of the century.
The following statistics were provided in 1998 for the UK: 1 in 3 women and 1 in 12 men over 50 are affected by osteoporosis. There are over 200,000 fractures each year: a broken bone every 3 minutes. More women die after hip fractures than from cancer of the ovaries, cervix and uterus. Osteoporosis costs £3,940 billion a year. Osteoporosis is increasing by 10% a year.
Women have a four-times greater risk of developing osteoporosis than men, with post-menopausal women at greatest risk. As levels of oestrogen fall after the menopause, the bone becomes porous and fragile, and the body's bone mass diminishes. Low oestrogen levels and increase in levels of circulating cortico-steroids are also responsible for loss of bone density in anorexics and and those who are overfit and underweight (e.g. athletes and dancers). This is particularly marked in young women, who can lose up to 15% of their bone density annually, whereas post-menopausal women tend only to lose 1 to 2% a year. Even after they were again eating well enough for their periods to have restarted, bone mass was only regained very slowly.