Calcium supplements

Calcium is a silvery, moderately hard metallic element that constitutes approximately 3 percent of the earth's crust and is a basic component of most animals and plants. Calcium is the most abundant, essential mineral in the human body. Calcium is the most abundant extracellular divalent cation in the body. In the average adult, it ranges from 1,000 to 1,300 g, of which about 99% is found in teeth and bone. The rest is present in extracellular fluid (ECF) and blood, with a smaller amount inside cells.

Along with phosphorus and other nutrients, calcium builds the hard structure that makes bones and teeth strong. Calcium is needed to form bones and teeth and is also required for blood clotting, transmission of signals in nerve cells, and muscle contraction. Calcium also helps the heart, nerves, muscles, and other body systems work properly. The physiological functions of calcium are so vital to survival that the body will demineralize bone to maintain normal blood calcium levels when calcium intake is inadequate. To function correctly, calcium must be accompanied by several other nutrients including magnesium, phosphorous, and vitamin A, vitamin C, vitamin D, and vitamin K. Vitamin D is needed to absorb calcium. Dairy products are widely heralded as a rich source of calcium. Other good sources include seaweeds, such as kelp, wakame and hijiki; nuts, beans and pulses, especially when taken raw; greens; wholemeal breads; fish.

Biological functions and health benefits of calcium

The body needs calcium to make strong bones. Calcium is necessary to help build and maintain healthy bones and strong teeth. The bones serve as a storage site for the body's calcium. They are continuously giving up calcium to the bloodstream and then replacing it as the body's need for calcium changes from day to day. 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.

Calcium levels often measure lower the week prior to one's menstrual period compared to the week after. Calcium supplementation helps relieve mood swings, food cravings, pain or tenderness, and bloating associated with premenstrual syndrome. Calcium is necessary to stabilize or allow for optimal activity of a number of proteins and enzymes. The binding of calcium ions is required for the activation of the seven "vitamin K-dependent" clotting factors in the coagulation cascade. Calcium can slow bone loss in postmenopausal women, may reduce premenstrual syndrome symptoms, and is associated with reduced risk of colorectal cancer. Research suggests that calcium, especially calcium derived from dairy products, may help to regulate body fat.

Diseases associated with calcium metabolism or deficiency

Hypercalcemia is an abnormally high level of calcium in the blood, usually more than 10.5 milligrams per deciliter of blood. Hypercalcemia per se can result in fatigue, depression, confusion, anorexia, nausea, vomiting, constipation, or increased urination; if it is chronic it can result in urinary calculi. Calcium is absorbed into the body in the small intestine. Its absorption is influenced by such factors as the amount of vitamin D hormone available to aid the process and the levels of calcium already present in the body. As much as 99% of the body's calcium is stored in bone tissue. A healthy person experiences a constant turnover of calcium as bone tissue is built and reshaped. The remaining 1% of the body's calcium circulates in the blood and other body fluids. The calcium levels are affected by vitamin D hormone and parathyroid hormone. The kidneys also help to control calcium levels. Hypercalcemia can occur when the concentration of calcium overwhelms the ability of the kidneys to maintain balance.

Osteoporosis is a disease of bone in which the amount of bone is decreased and the strength of trabecular bone is reduced, cortical bone becomes thin and bones are susceptible to fracture. It is predominantly characterised by a progressive atrophy (wasting away) of spongy bone, impaired mineralization, and fracture proclivity. Osteoporosis, which causes thin, porous, easily broken bones, may occur in women after menopause, but may sometimes occur in elderly men also. Osteoporosis in women past menopause is thought to be caused by a reduced amount of ovarian estrogen (a female hormone). Osteoporosis is influenced by hormonal levels and may be ameliorated by adequate calcium intake. Bone remodeling is heavily influenced by nutritional and hormonal factors. Calcium and vitamin D are nutrients required for normal bone growth.

Rickets is a childhood disorder involving softening and weakening of the bones. It is primarily caused by lack of vitamin D, calcium, or phosphate. When the body is deficient in vitamin D, it is unable to properly regulate calcium and phosphate levels. If the blood levels of these minerals become too low, other body hormones may stimulate release of calcium and phosphate from the bones to the bloodstream to elevate the blood levels. In children, symptoms of rickets include delayed sitting, crawling, and walking; pain when walking; and the development of bowlegs or knock-knees.

Dosage, intake, recommended daily allowance (RDA)

Getting the proper amount of calcium in the diet every day and participating in weight-bearing exercise (walking, dancing, bicycling, aerobics, jogging), especially during the early years of life (up to about 35 years of age) is most important in helping to build and maintain bones as dense as possible to prevent the development of osteoporosis in later life. Women who bleed excessively during menstruation may need to take a multivitamin and mineral supplement that contains iron to meet the daily recommendation of 15 mg.

Normal daily recommended intakes in milligrams (mg) for calcium are generally defined as follows:
Infants birth to 6 months: 210 mg
Infants 7 months to 1 year: 270 mg
Children 1 to 3 years: 500 mg
Children 4 to 6 years of age: 800 mg
Children 7 to 10 years of age: 800 mg
Adolescent and adult males: 800-1200 mg
Adolescent and adult females: 800-1200 mg
Pregnant and breastfeeding females under 19 years: 1,300 mg
Pregnant and breastfeeding females 19 years and older: 1,000 mg

Optimal calcium intake may vary according to a person's age, sex, and ethnicity. Calcium absorption also depends on the total amount of calcium consumed at one time and whether the calcium is taken with food or on an empty stomach. Most supplements provide 500 mg of calcium per serving, so take no more than 500 mg of calcium at one time to maximize absorption. Dietary sources are the best way to attain optimal calcium intake. A numerous amount of foods are rich in calcium, including dairy products (such as milk, yogurt, and cheese) and leafy green vegetables like turnip greens, broccoli, kale, and collards. Canned salmon, sardines, shrimp, and tofu are also high in calcium. Vitamin D helps prevent calcium loss from your bones. It is sometimes called 'the sunshine vitamin' because it is made in your skin when you are exposed to sunlight. The RDA for vitamin D is 400 IU (International units).

Types of calcium supplements

Calcium supplements are available as calcium carbonate, calcium citrate, calcium gluconate, or calcium lactate. The most common and generally least expensive form is calcium carbonate. Calcium carbonate may not be as effective as calcium citrate, but is less expensive. Calcium citrate is absorbed and digested by the body more effectively than calcium carbonate, particularly in the elderly, and appears to be more effective than calcium carbonate in preventing osteoporosis in postmenopausal women. Calcium lactate is used as strong acidifying calcium. Coral calcium has been heavily promoted by marketers. Coral calcium is derived from the calcium carbonate skeletons of coral. Corals are animals related to jellyfish and sea-anemones, these creatures secrete skeletons of calcium carbonate. Coral calcium is not very different from other sources of natural calcium carbonate such as oyster shells or limestone rock. Regardless of its origin, it is merely calcium carbonate, with some magnesium and trace amounts of many other minerals.

Side effects, precautions, drug interactions

Calcium supplements are generally well tolerated. For some people, some calcium supplements may cause side effects such as gas or constipation. Excessive amounts of calcium in the blood may cause nausea, vomiting, loss of appetite, increased urination, kidney toxicity, confusion, and irregular heart rhythm. Adverse conditions associated with high calcium intakes are hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals. High calcium intake from dairy products may actually increase a man's risk of prostate cancer. Calcium supplements may reduce the absorption of the antibiotic tetracycline. Calcium also interferes with iron absorption. High levels of calcium may increase the likelihood of a toxic reaction to digoxin. Calcium can interfere with the body's ability to absorb quinolone antibiotics. Avoid calcium from unrefined oyster shell, bone meal, or dolomite without the USP symbol, because it may contain high levels of lead or other toxic metals.