As was
discussed in a previous post, Dancers and Bone Health, bone tissue is
constantly being renewed until the age of about 35 when bone building, or
modeling, begins to slow down. At that
time, our bodies have to depend upon the bone tissue that was amassed during
the adolescent years to keep the bones healthy and strong.
Studies
have found that dancers’ bone mass measurements, or bone mineral density values,
are below what is expected and can cause stress fractures. This connection is discussed in detail in the
post Why Dancers May Be At Risk for Stress Fractures and Osteoporosis. In addition to engaging in weight bearing
activity to increase bone mineral density, dancers need to be concerned about
the amount of calcium they ingest.
Calcium
does many jobs in the body. It aids in
muscle contractions, sending messages throughout the nervous system, and
regulating hormone and enzyme levels, but its main job is to develop strong
bones. Most dancers do not get enough
calcium simply because they restrict caloric intake, and the foods that contain
the most concentrated amounts of calcium tend to be high in calories.
During the
teen years, calcium intake should be about 1300 mg/day, while adults should
ingest between 1000 and 1300 mg/day. An
important thing to remember is that calcium absorption is aided by vitamin
D. Sunlight is the best source of
vitamin D, but, unfortunately, our necessary use of sunblock prevents us from
absorbing it.
The best
way to meet our calcium and vitamin D needs is through dairy products like low-fat
milk, yogurt, or cheese. A 1996 study
found that calcium fortified orange and apple juices are also good sources of
readily absorbable calcium. (1)
Almond milk
is a good source of calcium for those who need to avoid dairy, providing more
calcium per serving than dairy milk, but it does not contain vitamin D. Other dietary sources of calcium are salmon
with bones, tofu, almonds, broccoli, kale, and spinach.
While
calcium intake can also be boosted with supplements, it is important to know
that a study conducted in 2007 found that those who ate calcium rich foods had
higher bone density values than those who relied upon calcium supplements.
(2)
Calcium
supplements are available as calcium citrate and calcium carbonate. Calcium citrate is 21% calcium and easily
absorbed by the body. Calcium carbonate
is 40% calcium but relies upon stomach acids to help absorption and needs to be
taken with food. It is also important to
know that calcium in absorbed best in doses equal to or less than 500 mg at a
time and that the body’s ability to absorb calcium decreases with age. (3)
Low bone
mineral density is a problem because it leads to weakened bones, stress
fractures, and osteoporosis. It is
important for dancers to amass as much bone tissue as possible when they are
young, and carefully monitoring their calcium intake is an important part of
that process.
(1) Andon, M.B., Peacock, M., Kanerva, R.L, & DeCastro, J.A. (1996). Calcium absorption from apple and orange juice fortified with calcium citrate malate. Journal of American College of Nutrition, 15(3), 313-6.
(2)Napoli, N., Thompson, J., Civitelli, R., Armamento-Villareal, R.C. (2007). Effects of dietary calcium compared with calcium supplements on estrogen metabolism and bone mineral density. American Journal of Clinical Nutrition, 85(5), 1428-33.
(3) Office of Dietary Supplements National Institutes of Health. (2012). Calcium [Fact Sheet]. Retrieved from http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/
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