Calcium
Calcium is the most abundant mineral in the body. It constitutes 1.5 to 2 percent of the total body weight, with more than 99 percent of the calcium being present in the bones. In addition to its major function in building and maintaining bones and teeth, calcium is also important in the activity of many enzymes in the body. The contraction of muscles, release of neurotransmitters, regulation of heartbeat, and clotting of blood are all dependent on calcium.
Calcium - Colon Cancer Prevention
Calcium supplementation has been shown to reduce the risk of colon cancer as well as to reduce the formation of polyps (precancerous lesions). It is thought that calcium binds to bile acids in the gut and neutralizes their cancer-causing effects.
Calcium - High Blood Pressure (hypertension)
Population studies have suggested a link between high blood pressure and a low dietary intake of calcium. Several clinical studies have demonstrated that calcium supplementation can lower blood pressure in hypertension, but the results have been inconsistent. It appears that calcium supplementation (1-1.5 g per day) is most likely to produce effective reductions in blood pressure in blacks, people who are salt sensitive and elderly patients. Typical reductions in blood pressure reported in these groups with calcium supplementation are around 10 mm Hg and 5 mg Hg for the systolic and diastolic readings respectively.
Another condition associated with high blood pressure that may respond to or be prevented by calcium supplementation is preeclampsia (a serious condition of pregnancy associated with elevations in blood pressure, fluid retention, and loss of protein in the urine). Early studies in pregnant women suggested that low calcium intake was a major risk factor for hypertension and preeclampsia during pregnancy. The results from clinical studies have now demonstrated that pregnant women who receive calcium supplementation during pregnancy have a reduced risk of hypertension and preeclampsia.
Calcium - Osteoporosis Treatment and Prevention
The body works very hard at maintaining blood levels of calcium. Even though the calcium in the blood represents only a small percentage of the total calcium in the body, it is critical to life that blood levels be maintained within a very narrow normal range. In addition to their structural role, the bones serve as a calcium reserve. Bone is constantly remodeling (breaking down and rebuilding) in order to maintain blood levels of calcium within the normal range. If a person does not get enough calcium from the diet or through supplementation, the body automatically takes calcium from the bones. If the body continues to tear down more bone than it replaces over a period of years in order to maintain blood calcium levels, it can lead to the crippling bone disease called osteoporosis. Approximately twenty-five million American women have some degree of osteoporosis; the disease will affect one-third to one-half of postmenopausal women. About five million American men suffer from osteoporosis as well.
Supplementation of calcium has been shown to be effective in both preventing and treating osteoporosis. Building bone density through calcium supplementation before menopause can help delay osteoporosis later in life, as there is a strong correlation between premenopausal bone density and the risk of osteoporosis. That being the case, building strong bones should be a lifelong goal beginning in childhood. However, most women probably are not concerned about osteoporosis until a few years before menopause. Fortunately, calcium supplementation does improve bone density in the time just before menopause (the perimenopause). In a two-year study, 214 perimenopausal women received either 1,000 or 2,000 mg of calcium. While the control group actually lost 3.2 percent of their spinal bone density, the calcium-treated groups increased their density by 1.6 percent (there was no difference between the two calcium groups). These results highlight the importance of calcium supplementation prior to menopause in the battle against osteoporosis. In postmenopausal women, although calcium supplementation by itself does not completely halt calcium loss, long-term studies have demonstrated that calcium supplementation does slow the rate down by at least 30 to 50 percent and offers significant protection against hip fractures.
Calcium - Premenstrual Syndrome
Numerous early studies suggested that disturbances in calcium regulation may underlie the hormonal disturbances characteristic of premenstrual syndrome and that calcium supplementation may be an effective therapeutic approach. Recently a well-designed double-blind, placebo-controlled study in nearly five hundred women with PMS demonstrated that supplementation with 1,200 mg of calcium (as calcium carbonate) over a three-month period was very effective in reducing seventeen core symptoms and four symptom factors (negative affect, water retention, food cravings, and pain). By the third month of use calcium effectively resulted in an overall 48 percent reduction in total symptoms compared with a 30 percent reduction achieved by placebo.
Calcium - Available Forms
Calcium supplements are available in capsules, tablets, chewable wafers, and liquids. The most widely used form is calcium carbonate. This form of calcium appears suitable for most people, with the possible exception of those who do not produce enough stomach acid. But even in these people it appears that taking the calcium carbonate with food overcomes the problem.
Calcium bound to citrate and other Krebs cycle intermediates such as fumarate, malate, succinate, and aspartate as well as lactate is probably the overall best forms of calcium. These substances have advantages over other forms of calcium in that they are (1) easily ionized, (2) almost completely broken down and utilized by the body, (3) virtually nontoxic, and (4) able to increase the absorption of not only calcium but other minerals as well. The problem with calcium supplements bound to these compounds is their bulk it basically requires three to four times as many capsules or tablets to provide the same level of calcium compared to calcium carbonate sources.The dosage range used for supplementation generally reflects the recommended dietary allowance (RDA) for calcium. In the treatment of osteoporosis.
The effectiveness of calcium supplementation at a particular dosage is ultimately dependent upon diet and lifestyle. Bone health and osteoporosis treatment/prevention involve much more than calcium. That being said, an effective dosage for supplemental calcium is 600 to 1,200 mg per day for most women. If there is significant bone loss, the dosage may need to be in the range of 1,000 to 1,500mg per day. For other applications such as colon cancer prevention and high blood pressure, a dosage of 1,000 to 1,500 mg per day is usual.
Calcium Side Effects
Calcium supplements are generally well tolerated at dosages less than 2,000 mg. Higher dosages may increase the risk for kidney stones and soft-tissue calcification; however, neither of these two conditions has been conclusively linked to calcium supplementation.Acute over dosage is rare. Excessive intake over several days or weeks may produce signs and symptoms related to over dosage. Early signs of an overdose are constipation (severe), dryness of mouth, headache (continuing), increased thirst, irritability, loss of appetite, mental depression, metallic taste, and unusual tiredness or weakness. Later signs of an overdose can include confusion, drowsiness (severe), and high blood pressure, increased sensitivity of eyes or skin to light, unusually large amount of urine or increased frequency of urination, and irregular, fast, or slow heartbeat.
Patients with hyperparathyroidism and cancer should not take calcium unless under the direct supervision of a physician.Aluminum-containing antacids are known to ultimately lead to an increase in bone breakdown and calcium excretion. Antiulcer drugs such as cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), omeprazole (Prilosec), and others can decrease calcium absorption because they block the output of hydrochloric acid.
The bone-building drugs alendronate (Fosamax), etidronate (Didronel), and risedronate (Actonel) as well as tetracycline antibiotics and thyroid hormones (e.g., levothyroxine, [Levoxyl, Synthroid]) should not be taken within two hours of calcium supplements, as the calcium may decrease their absorption and effectiveness. Calcium supplementation may also reduce the effectiveness of gallium nitrate (Ganite) and phenytoin (Dilantin). If you are taking one of these drugs, please consult your physician before taking a calcium supplement.
Absorption of calcium carbonate is enhanced when taken with food. Calcium interacts with many nutrients, especially vitamin D, vitamin K, and magnesium. Calcium absorption is negatively affected by high dosages of magnesium, zinc, fiber, and oxalates. Calcium excretion is increased by caffeine, alcohol, phosphates, protein, sodium, and sugar.
It is especially important that pregnant and lactating women receive enough calcium. Calcium supplementation is considered safe during pregnancy and lactation at dosages up to the RDA.
Children - Proper calcium intake is very important during childhood. Calcium supplements are suitable for children at dosages up to the RDA.
Seniors - No special precautions are known.