The effects of exercise on calcium status refers to the status of the mineral calcium in the body when a person exercises. The body does not produce calcium, and a diet rich in calcium combined with regular weight-bearing exercises like walking and running benefits bone health.
Calcium is the primary mineral that the body uses to build and maintain strong bones and teeth. More than 99% of the calcium in the body is stored in the bones and teeth. The remainder of the calcium is located in the blood, muscles, and in fluid between the cells. Additional nutrients associated with bone health include protein, vitamin D, vitamin K, potassium, phosphorus, fluoride, and vitamin C.
Calcium must be consumed daily because the body does not manufacture it. Food is the preferred source of this mineral, and calcium is found in foods including dairy products, leafy green vegetables, nuts, and calcium-fortified foods. Vitamin D helps the body absorb calcium. In some countries such as the United States and Canada foods such as milk are fortified with vitamin D. Calcium is also available as a dietary supplement.
Too little calcium in the diet leads to poor bone health and places people at risk of osteoporosis. The risk increases for people who do not do weight-bearing exercises such as walking, running, and playing basketball. People also need to do strength-training exercises to maintain their muscles.
Adequate calcium consumption and regular physical exercise are both vital for the growth and maintenance of bones and muscles. Physical activity enhances bone mass, which is the amount of bone tissue in the body. Peak bone mass is the genetic potential for bone density (thickness). Bones generally grow from childhood until a person is 30 years old. Bone mass decreases as people age, with a rapid decrease after a woman enters menopause. Excessive bone loss increases the risk for osteoporosis.
While bones grow, it is important that people achieve peak bone mass to compensate for the bone loss later in life. Bone loss can occur earlier if people fail to take in enough calcium. If a person fails to do this, the body takes calcium from the bones to use in other body functions.
Exercise before age 30 helps build bone mass. Physical activity after age 30 helps prevent bone loss. The federal Dietary Guidelines for Americans recommends that adults perform at least 30 minutes of moderate physical activity most days of the week.
Bone health is frequently the subject of scientific research on the effects of calcium status on exercise.
CALCIUM, EXERCISE, AND BONE HEALTH. A study described in the June 2003 issue of the America Journal of Clinical Nurition examined the effects of calcium intake and exercise on 131 girls between the ages of 16 and 18 in the United Kingdom. During the 15.5-month study, the subjects were randomly assigned to a group that exercised three times a week for 45 minutes and a group who did not exercise. Calcium supplements were given to 65 girls, and 66 received placebos. The researchers concluded that exercise and calcium enhanced bone mineral status. Whether this improvement led to optimized peak bone mass and a reduction of fracture risk could not be determined.
Exercise and a diet rich in calcium are crucial for people of all ages. Calcium is essential to bone growth and development, and is responsible for strong tooth enamel. Calcium is also important for muscle function, heart rhythm, and blood clotting. The mineral helps muscles and blood vessels expand and contract. In addition, calcium is used to send messages through the nervous system. The mineral helps to send hormones and enzymes through the body as well.
The amount of calcium that a person needs changes as the individual ages. Athletes should be evaluated to ensure they are maintaining sufficient levels of calcium in their bones and consuming adequate amounts of calcium in the diet.
The recommended dietary allowance (RDA) issued by the National Academy of Sciences is a general guideline for the daily intake of calcium. The RDA increases during the years that the bones of children and young adults are growing, when women are pregnant or breastfeeding, and as people age. Women over 50 need more calcium because of the effect of menopause on their bones. In addition, the efficiency of calcium absorption decreases as people age, according to the Office of Dietary Supplements (ODS) of the National Institutes of Health.
Although the RDA established the amount of calcium people should take each day, some individuals take more calcium than is necessary.
According to the Institute of Medicine Food and Nutrition Board, the daily tolerable upper level intake for calcium per day is:
Low calcium intake could cause calcium deficiency and put people at risk of lifelong harm to bone health. People who take too much calcium could become constipated, and are at risk for conditions including kidney failure.
Long-term calcium deficiency causes osteopenia, which is a bone mineral density (BMD) lower than the normal peak BMD but not low enough to be diagnosed as osteoporosis. The BMD is a measurement of the level of minerals in the bones, and indicates the thickness (density) of the bones. If osteopenia is not treated, it could lead to osteoporosis.
A person may be born with a low bone density, but gender is another cause of osteopenia and osteoporosis. While the aging process causes a decrease in bone mass in men and women, menopause causes a rapid decrease in density in women. Lack of physical activity puts people at risk of osteopenia, as does an eating disorder and being too thin.
Whereas osteopenia is characterized by weak bones, osteoporosis is characterized by brittle bones. A drop in the production of estrogen causes the bone loss associated with menopause. Bone density loss of from 3%–5% often occurs during the first years of menopause, according to the ODS. The rate of loss is less than 1% after a woman is 65. This drastic bone loss leaves bones so brittle that people are at more of a risk of fractures. The bones that break most often are in the hip, spine, and wrist.
The pace of rapid bone loss can be slowed by developing peak bone mass while bones are growing. This is accomplished by regularly taking calcium and doing weight-bearing and strength-training exercises. The exercise routine and daily calcium intake should continue through life to protect bones and slow the rate of bone loss.
Amenorrhea is the lack of a menstrual period. Primary amenorrhea is the lack of a menstrual period in a girl who is older than 15. Secondary amenorrhea is diagnosed when a girl has menstruated and does not have a period for three consecutive months. Some athletes and coaches mistakenly believe that it is not alarming when intense physical activity causes amenorrhea. The condition is caused by reduced estrogen levels that impair calcium levels and bone health.
The female triad consists of three interrelated conditions: disordered eating, disrupted menstrual cycle, and risks associated with low bone density. The athlete fails to consume enough calories to provide the energy used when exercising. The triad generally affects teenagers and college-age women who often avoid calcium-rich foods because they consider them fattening. Triad conditions put the athlete at risk for broken bones, osteopenia, and osteoporosis.
Conditions associated with consuming too much calcium include hypercalcemia, which is an excessive level of calcium in the blood. Hypercalcemia places people at risk of conditions including kidney failure, kidney stones, and high urinary levels of calcium. It is usually caused by taking in too much calcium from food or supplements. People with these conditions should consult with their doctor to determine how much calcium should be in their diet.
People, especially athletes, may choose to raise the amount of calcium they consume, mistakenly thinking that it will better protect their bones. From 2003–2006, about 5% of women age 50 and older exceeded their calcium intake by 300–360 mg, according to the United States National Health and Nutrition Examination Survey. The calcium consumption consisted of food and supplements.
Exceeding maximum calcium limits can cause constipation. Furthermore, higher calcium intake could increase the risk for conditions including kidney stones, prostrate cancer, calcium build-up in the blood vessels, and impaired absorption of iron and zinc.
See also Amenorrhea ; Bone health ; Drug interactions; Fatigue ; Fracture ; Osteoporosis ; Protein ; Walking .
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Stear, Samanttha J., et. al. “Effect of a Calcium and Exercise Intervention on the Bone Mineral Status of 16—18-y-old Adolescent Girls.” America Journal of Clinical Nurition 77 (June 2003): 985–92. http://www.ajcn . org/content/77/4/985.full.pdf (accessed January 14, 2017).
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The National Osteoporosis Foundation (NOF), 251 18th Street S, Suite 630, Arlington, VA, 22202, (800) 231-4222, email@example.com, https://www.nof.org/ .