Calcium is an element critical to many body functions, including bone growth and maintenance, muscle and nerve control, blood clotting, and blood pressure regulation. Bone mass is built until age 29 years or so. After that, you cannot build more bone by increasing your calcium intake, but you can help prevent bone loss by maintaining a good intake of calcium and vitamin D and exercising regularly.
There are two types of calcium. One type of calcium is tightly bound within the bone and the other more accessible type of calcium is found on the bone. The skeleton serves as a bank of minerals for the body. The body can borrow from the skeletal stores when blood calcium levels drop and return calcium to bones as needed.
A constant supply of calcium is necessary throughout our lifetime, but is especially important during phases of growth, pregnancy, and lactation (breast feeding). About 10-40% of dietary calcium is absorbed in the small intestine with the help of vitamin D. The level of calcium absorption from dietary sources drops to 7 in post-menopausal women. The body will absorb more calcium if there is a deficiency. Factors that improve calcium absorption include adequate amounts of protein, magnesium, phosphorous, and vitamin D. Conditions that reduce calcium absorption include high or excessive intakes of oxalates and phytates, found in foods such as spinach and unleavened whole wheat products. Consumption of alcohol, coffee, sugar, or medications such as diuretics, tetracycline, aluminum containing antacids, or stress can reduce absorption of calcium. Those who have had prolonged bed rest, diet intensively, and/or inadequate vitamin D intake are also at risk to lose bone mass. Lack of exercise can reduce calcium absorption as well as cause an increase in calcium losses. These life habits can immobility lead to calcium deficiency. Calcium deficiency can increase risk of bone disorders such as osteoporosis and is usually diagnosed in later years through bone density studies.
Functions of Calcium
- Responsible for construction, formation and maintenance of bone and teeth. This function helps reduce the occurrence of osteoporosis.
- A vital component in blood clotting systems and also helps in wound healing.
- Helps to control blood pressure, nerve transmission, and release of neurotransmitters.
- An essential component in the production of enzymes and hormones that regulate digestion, energy, and fat metabolism.
- Helps to transport ions (electrically charged particles) across the membrane.
- Is essential for muscle contraction.
- Assists in maintaining all cells and connective tissues in the body.
- Helpful to reduce the incidence of premature heart disease, especially if adequate intakes of magnesium are also maintained.
- Help to prevent periodontal disease (gum disease).
- Birth - 6 months: 210 mg
- 6 to 12 months: 270 mg
- 1 to 3 years: 500 mg
- 4 to 8 years: 800 mg
- 9 to 18 years: 1300 mg
- 19 to 50 years: 1000 mg
- 50+ years: 1200 mg
Toxicity from calcium is not common because the gastrointestinal tract normally limits the amount of calcium absorbed. Therefore, short-term intake of large amounts of calcium does not generally produce any ill effects aside from constipation and an increased risk of kidney stones. However, more severe toxicity can occur when excess calcium is ingested over long periods, or when calcium is combined with increased amounts of vitamin D, which increases calcium absorption. Calcium toxicity is also sometimes found after excessive intravenous administration of calcium. Toxicity is manifested by abnormal deposition of calcium in tissues and by elevated blood calcium levels (hypercalcemia). However, hypercalcemia is often due to other causes, such as abnormally high amounts of parathyroid hormone. Usually, under these circumstances, bone density is lost and the resulting hypercalcemia can cause kidney stones and abdominal pain. Some cancers can also cause hypercalcemia, either by secreting abnormal proteins that act like parathyroid hormone or by invading and killing bone cells causing them to release calcium. Very high levels of calcium can result in appetite loss, nausea , vomiting, abdominal pain, confusion, seizures, and even coma.
If your food intake of calcium is too low, take an over the counter calcium supplements. Multivitamins do not contain enough calcium. The best researched calcium supplements are calcium carbonate and calcium citrate. Read labels carefully, insure adequate elemental calcium (i.e. the amount available for absorption by your body).
Exercising regularly will help maintain bone density, agility, and strength, making falls less likely and falls that do occur less likely to cause fracture. Exercise on average four times a week, thirty minutes each time. Weight bearing exercises are best: walking, jogging, dancing, weight lifting, etc. Water sports, swimming and bicycling are not weight bearing exercises but will help your cardiovascular health and muscle fitness.
- Somer E. Minerals. In: The Essential Guide to Vitamins and Minerals, New York, NY Harper Perennial: New; 1995; 89-94.
- Smith KT 1987. "Calcium absorption from a new calcium delivery system (CCM)." Calcif Tissue Int. 41(6):3 51-2.
- Whitney EN, Rolfes SR. Water and the Major Minerals. In: Understanding Nutrition. Seventh Edition, St. Paul, MN: West Publishing Company; 1996; 448-454.