Bone Loss

Bone loss occurs when bone deterioration (resorption) outpaces new bone growth, leading to a brittle skeleton.

• Although bones may seem like hard and lifeless structures, bones are living tissues with blood supply and active metabolism.
• Bones respond to exercise and a healthy diet by becoming stronger. Strong bones are important for health.
• Bones make up our skeletons and provide structure and support for our bodies. However, bones also act as a storehouse for minerals that our bodies need, especially calcium.
• During a person's lifetime, the body constantly breaks down old bone (through a process called resorption) and builds up new bone.
• Any time old bone is broken down faster than new bone is made, net bone loss occurs. Bone loss can lead to low bone density (osteopenia), weakness of the bone, and eventually osteoporosis. This can lead to bone fractures (broken bones), even with minimal trauma.
• Osteoporosis (or porous bone) is a disease in which bones become weak and fragile. Porous bones have increased fracture risk and are more likely to break.
• Osteoporosis is a serious disease that affects millions of people worldwide. Without prevention or treatment, osteoporosis can progress without pain or symptoms until a bone breaks (fractures).
• Fracture from weak bones commonly occurs in the hip, spine (vertebral), and wrist.

Bone is made mostly of collagen, a protein that is woven into a flexible framework. Bone also contains calcium phosphate and calcium carbonate, minerals that add strength and harden the framework. The combination of calcium and collagen gives the bone its strength and flexibility. The flexibility (or ability to withstand stress) of the bone protects it from breaking. Bone is strong because of calcium, but bone also acts as a storehouse for calcium. In fact, more than 99% of the body's calcium is contained in the bones and teeth. The remaining 1% is in the blood.

Even though it is mostly made of protein and minerals, bone is living, growing tissue. Throughout a person's lifetime, old bone is broken down (a process called resorption) and new bone is added to the skeleton (formation). When more bone is broken down than is added to the skeleton, bone loss occurs.

Bone loss occurs when more bone is resorbed than is formed by the body. Many factors determine how much old bone is resorbed and how much new bone is made. Some factors people have control over (such as diet), but some factors are out of their control (such as age).

Most new bone is added during childhood and teenage years. As a result, bones become larger, heavier, and stronger (denser). Bone formation continues until the peak bone mass (maximum solidness and strength) is reached. Peak bone mass (or bone density) is reached around age 30. After age 30, bone resorption slowly begins to exceed new bone formation. This leads to bone loss. Bone loss in women occurs fastest in the first few years after menopause, but bone loss continues into old age.

Factors that can contribute to bone loss include having a diet low in calcium, not exercising, smoking, and taking certain medications such as corticosteroids.

Corticosteroids are medications prescribed for a wide range of diseases, including arthritis, asthma, inflammatory bowel disease, lupus, and other diseases. Corticosteroids may cause osteoporosis when used chronically.

Men are also at risk for bone loss. Even though bone loss usually occurs later in life compared to women, men can still be at high risk for osteoporosis. By age 65, men catch up to women and lose bone mass at the same rate. Additional risk factors such as a small body frame, long-term use of corticosteroids (which are medications prescribed for a wide range of diseases, including arthritis, asthma, Crohn's disease, lupus, and other diseases), or low testosterone (or sex hormone) levels can increase the risk of osteoporosis in men.

Many factors lead to bone loss. Some factors, such as age, cannot be controlled. However, simple steps can be taken to prevent or slow bone loss (see Prevention of Osteoporosis, Treatment of Osteoporosis, and Understanding Osteoporosis Medications).

Eat a Diet High in Calcium

Not getting enough calcium during a person's lifetime significantly increases the risk of developing osteoporosis. A low-calcium diet is associated with low bone mass, rapid bone loss, and broken bones (see Osteoporosis and Calcium). A diet high in calcium is important. Good sources of calcium include the following:

• Low-fat dairy products, such as milk, yogurt, cheese, and ice cream
• Dark green leafy vegetables, such as broccoli, collard greens, and spinach
• Sardines and salmon with bones
• Tofu
• Almonds

Some foods have added calcium, such as orange juice, cereals, and bread. Calcium supplements are also available.

Eat a Diet High in Vitamin D

Vitamin D is important for the body to absorb calcium from the diet. Without enough vitamin D, people are unable to absorb calcium from the foods they eat. When not enough calcium is absorbed from foods, the body has to take calcium from the bones, causing bone loss and leading to weaker bones.

Vitamin D comes from two sources. Vitamin D is made in the skin through direct exposure to sunlight, and it comes from the diet. Many people get enough vitamin D naturally. It is also found in fortified dairy products, egg yolks, saltwater fish, and liver. However, vitamin D production decreases in older people, in people who are housebound, and during the winter. These people may need vitamin D supplements to ensure a daily intake of 400-800 IU of vitamin D.

Exercise

Physical activity during childhood and adolescence increases bone density and strength. Children who regularly exercise are more likely to reach their peak bone density (maximum strength and solidness) than those that do not exercise. People who reach their peak bone density, which usually occurs by age 30 years, are less likely to have a significant bone loss that leads to osteoporosis.

The best exercise to prevent bone loss is a weight-bearing exercise that works against gravity. These kinds of exercises include walking, hiking, jogging, climbing stairs, playing tennis, and dancing. The second type of exercise is resistance

Elderly people, people with osteoporosis, and people who have not exercised for most of the adulthood should check with their health-care provider before beginning any exercise program.

Quit Smoking

Smoking is bad for the bones as well as for the heart and the lungs. Women who smoke have lower estrogen levels compared to women who do not smoke. Lower estrogen levels lead to increased bone loss. Women who smoke often go through menopause earlier. Remember that bone loss is most rapid in the first few years after menopause, but it continues even in the postmenopausal years. This means that the earlier menopause occurs, the more years bone loss is experienced and the weaker the bones will become over time. Men and women who smoke may absorb less calcium from their diets. Less calcium from the diet means the body breaks down the bones for the calcium it needs, which leads to bone loss.

Limit Alcohol Intake

Regular consumption of 2-3 ounces of alcohol a day may be damaging to bones, even in young women and men. Heavy drinkers are more likely to have bone loss and fractures. This is related to both poor nutrition and increased risk of falling. However, some evidence indicates that moderate alcohol intake may have beneficial effects on bone mass.

Various drugs, vitamins, and minerals are used to prevent osteoporosis in women. Except for calcium and vitamin D supplementation, drug therapy to prevent osteoporosis in men is still investigational.

• Dietary phytoestrogens found in soy products and legumes are not potent enough to justify their use as a treatment for osteoporosis, but they may be useful in delaying or preventing osteoporosis as part of a healthy lifestyle that includes a calcium-rich diet and exercise.
• Calcium and vitamin D are essential for reducing bone loss. In order for other preventive medications to be effective, adequate calcium and vitamin D blood levels are needed.
• Estrogen replacement therapy in postmenopausal women slows bone loss and is proven to prevent osteoporosis. However, hormone therapy is associated with certain medical risks. The decision about hormone therapy is a very individual decision in which the patient and doctor must take into account the inherent risks and benefits of the treatment along with each woman's own medical history. Other effective preventive and treatment options for osteoporosis exist, and more are being developed to avoid increasing hormone-related risks.
• Selective estrogen receptor modulators (SERM) include the drug raloxifene (Evista). SERMs preserve bone density but are not associated with estrogen-related risk factors such as uterine cancer.
• Bisphosphonates are medications that slow bone loss by increasing bone formation and decreasing bone turnover. Adequate calcium and vitamin D blood levels are required for bisphosphonates to be effective. Bisphosphonates are used for prevention and treatment of osteoporosis. The drugs alendronate (Fosamax), ibandronate (Boniva), and risedronate (Actonel) are examples of bisphosphonates.

The only reliable way to detect bone loss is to have a bone mineral density (BMD) test. Bone density tests are very sensitive in detecting bone loss. People with strong risk factors for osteoporosis should have a BMD test. Risk factors include the following:

• Estrogen deficiency from early menopause (age < 45 years), the absence of menstrual periods (amenorrhea for > 1 year), or hypogonadism (impaired gonads, which are the ovaries or testes, or impaired sex hormones, which are estrogen or testosterone)
• Long-term corticosteroid or anticonvulsant (antiseizure) drug therapy
• The family history of hip fracture
• Low body mass index (BMI)
• Chronic disorders associated with osteoporosis, such as anorexia nervosa or liver disease
• Previous broken bones related to having weak bones
• Loss of height (widow's hump)
• Female sex
• Asian or white race
• Poor diet without enough calcium
• Lack of exercise
• Smoking
• Regular use of large amounts of alcohol

Recommendations in the United States are that all women 65 years and older should have a BMD test. Postmenopausal women younger than 65 years who have one or more risk factors (in addition to being postmenopausal and female) should have a BMD test. Tests that are used to measure BMD include dual energy x-ray absorptiometry (DXA), quantitative computed tomography (QCT), and quantitative ultrasound (QUS). See Bone Mineral Density Tests for more information.

National Osteoporosis Foundation

International Society for Clinical Densitometry Headquarters