Calcium's role in health and disease prevention
Calcium and bone health
Your bones are living tissues and continue to change throughout life. During childhood and adolescence, bones increase in size and mass. Bones continue to add more mass until around age 30, when peak bone mass is reached. Peak bone mass is the point when the maximum amount of bone is achieved. Because bone loss, like bone growth, is a gradual process, the stronger your bones are at age 30, the more your bone loss will be delayed as you age. Therefore, it is particularly important to consume adequate calcium and vitamin D throughout infancy, childhood, and adolescence. It is also important to engage in weight-bearing exercise to maximize bone strength and bone density (amount of bone tissue in a certain volume of bone) to help prevent osteoporosis later in life. Weight bearing exercise is the type of exercise that causes your bones and muscles to work against gravity while they bear your weight. Resistance exercises such as weight training are also important because they help to improve muscle mass and bone strength.
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Examples of weight bearing exercise
- walking
- running
- dancing
- aerobics
- skating
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Examples of NON-weight bearing exercise
- swimming
- bicycling
- water aerobics
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Osteoporosis is a disorder characterized by porous, fragile bones. It is a serious public health problem for more than 10 million Americans, 80% of whom are women. Another 34 million Americans have osteopenia, or low bone mass, which precedes osteoporosis. Osteoporosis is a concern because of its association with fractures of the hip, vertebrae, wrist, pelvis, ribs, and other bones. Each year, Americans suffer from 1.5 million fractures because of osteoporosis.
Osteoporosis and osteopenia can result from dietary factors such as:
- chronically low calcium intake
- low vitamin D intake
- poor calcium absorption
- excess calcium excretion
When calcium intake is low or calcium is poorly absorbed, bone breakdown occurs because the body must use the calcium stored in bones to maintain normal biological functions such as nerve and muscle function. Bone loss also occurs as a part of the aging process. A prime example is the loss of bone mass observed in post-menopausal women because of decreased amounts of the hormone estrogen. Researchers have identified many factors that increase the risk for developing osteoporosis. These factors include being female, thin, inactive, of advanced age, cigarette smoking, excessive intake of alcohol, and having a family history of osteoporosis.
In 1993 the FDA authorized a health claim for food labels on calcium and osteoporosis in response to scientific evidence that an inadequate calcium intake is one factor that can lead to low peak bone mass and is considered a risk factor for osteoporosis. The claim states that "adequate calcium intake throughout life is linked to reduced risk of osteoporosis through the mechanism of optimizing peak bone mass during adolescence and early adulthood and decreasing bone loss later in life".
Various bone mineral density (BMD) tests, including those that measure your hip, spine, wrist, finger, shin bone, and heel, can help determine bone mass. These tests provide a T-score which is a measure of bone mineral density that compares an individual's BMD to an optimal BMD of a 30 year old healthy adult. See Figure 2 below. A T-Score of -1.0 and above indicates normal bone density. A T-score of -1.0 to -2.5 indicates that a person is considered to have low bone mass (osteopenia). A score below -2.5 indicates osteoporosis.
Although osteoporosis affects people of different races, genders and ethnicities, women are at highest risk because their skeletons are smaller to start with and because of the accelerated bone loss that accompanies menopause. Adequate calcium and vitamin D intakes, as well as weight bearing exercise are critical to the development and maintenance of healthy bone throughout the lifecycle. Older adults should strive to maintain recommended daily calcium intakes as well as an adequate vitamin D intake.
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