Osteoporosis is a chronic disease in which the mineral content of the bones progressively decreases so that the bones become brittle and are easily broken. It is linked to more than 1 million fractures of the hip, spine, and other bones each year. Vertebral bones in the spine shrink and fracture, causing a deformed spine. Bones in the wrist are also common fracture’ sites. Some 25 million Americans are affected by osteoporosis, 80% of whom are postmenopausal women. Although postmenopausal white and Asian women are at highest risk, men and women of all ages and ethnicities can be affected.
Though bones may seem hard, they are made of living cells that require calcium and vitamin D (necessary for optimum absorption of calcium) to grow and stay strong. Almost all of the body’s calcium stores are located in bone. During growth and development, bones typically receive more calcium than they give up. By age 25, when bone density peaks, calcium absorption levels off; at age 30, the bone-building process is over. This is when bone mass maintenance and calcium are especially important. If blood levels of calcium drop, the body withdraws what it needs from its bones. With adequate dietary intake of calcium, bones are spared the effects of calcium depletion that may accelerate osteoporosis.
Calcium is not the only factor associated with bone loss. Estrogen depletion during menopause triggers bone loss up to 1 % a year. By the time a woman is 80, she may have lost 30% to 40% of her bone mass. When bone-mass loss becomes excessive, it may not take even a fall to fracture bones. Simply bending over and lifting 25 pounds-a heavy bag of groceries-could cause injury. During menopause, hormone-replacement therapy in the form of estrogen supplementation is recommended for many women as protection against osteoporosis.
Because nicotine is thought to decrease blood levels of estrogen, smoking also contributes to bone loss. Smokers go through menopause on average at least 2 years earlier than nonsmokers. Genetics may also play a role in osteoporosis. Researchers have identified an osteoporosis gene that determines how well vitamin D facilitates the absorption of calcium. People who have the gene are more resistant to absorbing available calcium. Caffeine and alcohol have also been implicated in bone loss. A recent study found that women who drank two or more cups of caffeinated coffee a day and drank no milk experienced significant loss of bone density after menopause. The effects of caffeine can be negated with consumption of milk. In the same study, coffee drinkers who drank at least one glass of milk per day had 6.5% higher bone density than the coffee only group.
The National Osteoporosis Foundation recommends several simple steps to reduce the risk of contracting this disease. First, consume adequate amounts of calcium, preferably from food. If this doesn’t work, calcium supplements are recommended. The Foundation suggests 1500 mg, which is almost double the amount given in the RDA. 25 Second, consume enough vitamin D (400 IU) to permit absorption of the calcium. Third, consider hormone-replacement therapy (estrogen) and discuss its use with your medical doctor, especially if there is a family history of osteoporosis. And fourth, participate in weight-bearing activities, such as walking, running, and weight training, to prevent bone loss. In one study, women who participated in a year-long exercise program and received daily doses of estrogen experienced a 7% increase in bone density and fared better than women on estrogen alone. Physical exercise forces bones to adapt to the stresses imposed on them, and they hypertrophy in response. Bones atrophy when they are unstressed.
People with osteoporosis can and should exercise, but the type of physical activity and the intensity of exercise must be carefully selected. Forceful contractions of muscles and high-impact activities should be avoided because they may stress the bones beyond their breaking point. Swimming, water aerobics, stationary cycling, walking, and light weight training are good starting activities for those with osteoporosis.