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Boning Up on Bone Health
What are your plans for retirement? Are you saving for your financial future with an IRA or a work retirement account? Are you watching your fat and cholesterol intake to keep your heart healthy? Are you taking steps to prevent osteoporosis and ensure the health of your bones?
Most of us do not think about the health of our bones very often. We tend to take their supporting presence for granted. But perhaps we shouldn’t. Without strong bones, many daily activities such as grocery shopping, house cleaning, and walking can become increasingly difficult to do.
Osteoporosis, a disease that causes bones to weaken and fracture, can have surprisingly broad effects on the quality and length of your life. Your risk of developing osteoporosis is influenced by your genetic background, your lifestyle, and even your diabetes. Because most people are not aware that they have osteoporosis until bone loss is serious, it is important to take steps to prevent or slow bone loss early, before significant problems occur.
Bone growth and loss
Although some loss of bone mass is a natural part of aging, when bone tissue is lost too quickly, or rebuilding of bone is too slow, osteoporosis can develop. Osteoporosis is more likely to occur in people who do not reach their maximum potential bone mass when they are young. Reasons for not reaching maximum potential bone mass include poor nutrition (particularly inadequate calcium and vitamin D intake), chronic or prolonged illness, and drug side effects.
Osteoporosis can affect any bone, but fractures of the wrist, hip, and spine are most common. One in two women and one in four men over age 50 will have an osteoporosis-related fracture in their lifetime. Hip fractures usually require surgery and hospitalization to repair, and they can permanently reduce mobility. In fact, 85% of people who have had a hip fracture cannot walk unaided across a room six months later. Degradation or collapse of spinal bone tissue can also decrease mobility and is often very painful. Since many fractures occur when a person falls, taking steps to prevent falls can reduce the risk of bone fractures. (See “Preventing Falls and Fractures” for tips on staying upright.)
Risk factors for osteoporosis
Genetics. Your genes influence your peak bone mass and your rate of bone loss as you age. Genetics may also influence how likely you are to experience a bone fracture. If your parents or grandparents had osteoporosis, you are at high risk of developing it too. You can’t change your genes, but you can control other risk factors for osteoporosis.
Sex. Women are four times more likely than men to develop osteoporosis. This is because women tend to have smaller bones than men and because hormonal changes in menopause dramatically increase the rate of bone loss. Women can lose up to 20% of their bone mass in the five to seven years following menopause.
Age. Because the ability of the body to build bone decreases as you age, the older you are, the greater your risk of osteoporosis. People who reach a higher peak bone mass when they are young are better protected against age-related bone loss.
Ethnicity. People of Latino and African-American heritage have a lower risk for osteoporosis than people of Caucasian and Asian ethnicity. But this does not mean that osteoporosis is not a concern for Latinos and African-Americans; it is, and they also need to control the risk factors that they can.
Body size. The size of your bones influences your risk of developing osteoporosis. People with small bones and a thin body build are at greater risk than people who have large, dense bones. People who weigh more often have stronger bones because bone is stimulated to grow and make new tissue by weight-bearing activity. Women who weigh more may also produce greater amounts of estrogen. Eating disorders like anorexia can cause severe loss of bone tissue and greatly increase the risk of having osteoporosis at a young age.
Hormone levels. The sex hormones, estrogen in women and testosterone in men, protect against bone loss. When hormone levels are low, the rate of bone loss increases. Hormone levels are decreased in amenorrhea (the abnormal loss of menstrual periods in young women) and menopause. Medroxyprogesterone (brand name Depo-Provera), an injectable contraceptive, may also cause bone loss.
Nutrition. Adequate levels of many nutrients, including calcium, vitamin D, magnesium, and vitamin K, are necessary to build healthy bones. The most important of these are calcium and vitamin D. Bones and teeth hold more than 99% of the body’s calcium stores. If your dietary calcium intake is low, the body pulls calcium from bone stores to perform other necessary functions in the body. Chronic low calcium intakes cause calcium loss from bones, weakening them. Vitamin D is necessary for absorption and use of calcium in the body, and low levels are also associated with increased osteoporosis and fractures. (For more about calcium, read “The Calcium Connection.”)
Conditions such as food allergies, Crohn disease, and intestinal surgery that limit food intake or decrease absorption of nutrients can also increase risk of osteoporosis. In addition, excessive intake of retinol, a form of vitamin A, has been shown to interfere with normal bone metabolism and to increase the risk of fractures. The upper intake limit for retinol is 600 micrograms for children up to 3 years, 900 micrograms for children 4-8 years, 1700 micrograms for children 9–13 years, 2800 micrograms for teens 14–18 years, and 3,000 micrograms for people 19 and older. The upper intake level does not include beta-carotene, a nutrient found in plant foods that is converted to vitamin A in the body. Retinol is found in animal products; vitamin supplements; fortified foods such as milk, cereals, and energy bars; and skin preparations.
Activity level. A low physical activity level is a risk factor for osteoporosis. Exercise, particularly weight-bearing activities where your body is working against gravity, can help keep bones strong. Weight-bearing activities include walking, dancing, climbing stairs, and weight training. Balance exercises are also useful to prevent falls that could lead to fractures.
Smoking. Smoking can decrease estrogen levels and may promote early menopause in women. Smoking-related bone loss is a major risk factor for osteoporosis.
Alcohol intake. Regular consumption of more than one to two servings of alcohol a day can be toxic to bone cells and can prevent bone from growing and rebuilding itself. Alcohol use can also decrease absorption of nutrients from food, change calcium and vitamin D metabolism, and increase risk of falls and incidence of fractures.
Medicines. Some drugs can increase the risk of osteoporosis by decreasing the ability of bone cells to make new bone or increasing the breakdown of bone, decreasing calcium absorption and metabolism, or changing hormone levels. Drugs can also increase the risk of having a fall-related fracture if they cause dizziness. Common drugs that can lead to osteoporosis include glucocorticoids, such as prednisone, some anticonvulsants, such as phenytoin (Dilantin), hormones used to treat endometriosis, and too much thyroid medicine. Excessive use of aluminum-containing antacids can decrease calcium absorption.
Diabetes and bones
People who develop Type 1 diabetes in childhood or adolescence tend to have decreased bone mass as adults and are more likely to develop osteoporosis and experience fractures than people who don’t have diabetes. It is thought that lack of insulin, which is a growth factor for bone, causes poor bone growth and lower peak bone mass in adolescents with Type 1 diabetes. High blood glucose levels may also cause poor bone growth, though studies of blood glucose control and bone mineral density have not always shown a link between the two.
People with Type 1 diabetes have also been shown to have reduced levels of vitamin D on diagnosis and abnormal seasonal changes in vitamin D levels, which could contribute to poor bone growth. Other conditions that can increase risk of osteoporosis, such as gluten intolerance (also called celiac disease) and thyroid disorders, are also more common in Type 1 diabetes.
Research studies of people with Type 2 diabetes have found increases, decreases, and no change in bone mineral density associated with diabetes. It is true that people with higher body weights tend to be protected against bone loss, and many people with Type 2 diabetes are overweight, but several studies have found that people with Type 2 diabetes experienced a greater number of fractures than people without diabetes, while others have found significant bone loss in people with Type 2 diabetes compared to age- and sex-matched control subjects. Other studies have found low serum vitamin D levels in postmenopausal women with Type 2 diabetes.
No matter what type of diabetes a person has, diabetes-related complications such as hypoglycemia, retinopathy and vision loss, and changes in balance caused by neuropathy, can increase the risk of falls and fractures.
After you get your bone mineral density tested, your physician will compare your results against a “normal” standard. One standard, the T-score, compares your bone mineral density to an average, healthy 30-year-old’s bone density. The other standard, the Z-score, compares your bone mineral density to that of a typical healthy person of your age and body size. Because most people lose bone as they age, the age-matched Z-score is less useful in determining risk.
T-scores and Z-scores are measured as a standard deviation, or how different your measurement is from normal. Bone mineral density values that are one standard deviation or less from normal are considered healthy. T-scores that are more than one standard deviation below normal but less than 2.5 standard deviations below normal indicate osteopenia, or low bone mass. Scores that are more than 2.5 standard deviations below normal indicate osteoporosis.
Prevention and treatment
Even if you have passed the time period when bone is built most efficiently (from preadolescence until about 30), there is still a great deal you can do to preserve the bone you have. To avoid osteoporosis, or to slow bone mass loss if you already have osteoporosis, take the following steps to control your risk factors:
There are also several different types of medicines that may help slow bone loss or strengthen bone in those diagnosed with osteoporosis. These include the following:
No time like the present
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