The most complete growth and nutrition guide is here for all your herbs, vitamins, and minerals.

The Complete Guide To Nutritional Herbs, Vitamins, And Minerals

Calcium is the most abundant mineral in the body, making up nearly 2% of total body weight. More than 99% of the calcium in your body is found in your bones, but the other 1% is perhaps just as important for good health. Many enzymes depend on calcium in order to work properly, as do your nerves, heart, and blood-clotting mechanisms. To build bone, you need to have enough calcium in your diet. But in spite of calcium-fortified orange juice and the best efforts of the dairy industry, most Americans are calcium deficient.1 Calcium supplements are a simple way to make sure you're getting enough of this important mineral. One of the most important uses of calcium is to prevent and treat osteoporosis, the progressive loss of bone mass to which postmenopausal women are especially vulnerable. Calcium works best when combined with vitamin D. Other evidence suggests that calcium may have another important use: reducing PMS symptoms.

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Requirements/Sources

Although there are some variations between recommendations issued by different groups, the official U.S. and Canadian recommendations for daily intake of calcium are as follows:

Infants 0–6 months, 210 mg 7–12 months, 270 mg Children 1–3 years, 500 mg 4–8 years, 800 mg Males and females 9–18 years, 1,300 mg 19–50 years, 1,000 mg 51 years and older, 1,200 mg Pregnant women 1,000 mg (1,300 mg if under 19 years old) Nursing women 1,000 mg (1,300 mg if under 19 years old)

To absorb calcium, your body also needs an adequate level of vitamin D (for more information, see the article on vitamin D). Milk, cheese, and other dairy products are excellent sources of calcium. Other good sources include orange juice or soy milk fortified with calcium, fish canned with its bones (e.g., sardines), dark green vegetables, nuts and seeds, and calcium-processed tofu.

Naturally Derived Forms of Calcium

These forms of calcium come from bone, shells, or the earth: bonemeal, oyster shell, and dolomite. Animals concentrate calcium in their shells, and calcium is found in minerals in the earth. These forms of calcium are economical, and you can get as much as 500 to 600 mg in one tablet. However, there are concerns that the natural forms of calcium supplements may contain significant amounts of lead.2 The level of contamination has decreased in recent years, but still may present a health risk.3,4 Calcium supplements rarely list the lead content of their source, although they should. The lead concentration should always be less than 2 parts per million.

Refined Calcium Carbonate

This is the most common commercial calcium supplement, and it is also used as a common antacid. Calcium carbonate is one of the least expensive forms of calcium, but it can cause constipation and bloating, and it may not be well absorbed by people with reduced levels of stomach acid. Taking it with meals improves absorption, because stomach acid is released to digest the food.121 (See Chelated Calcium.)

Chelated Calcium

Chelated calcium is calcium bound to an organic acid (citrate, citrate malate, lactate, gluconate, aspartate, or orotate). The chelated forms of calcium offer some significant advantages and disadvantages compared with calcium carbonate. Certain forms of chelated calcium (calcium citrate and calcium citrate malate) are widely thought to be significantly better absorbed and more effective for osteoporosis treatment than calcium carbonate. However, while some studies support this belief (6, 7, 9, 10) others do not (8).122,123 The discrepancy may be due to the particular calcium product used; some calcium carbonate formulations may dissolve better than others. Chelated calcium is much more expensive and bulkier than calcium carbonate. In other words, you have to take larger pills, and more of them, to get enough calcium. It is not at all uncommon to need to take five or six large capsules daily to supply the necessary amount, a quantity some people may find troublesome. The form of calcium found in beverages is usually the chelated form, calcium citrate malate, or a slightly less well absorbed form, tricalcium phosphate.

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Therapeutic Dosages

Unlike some supplements, calcium is not taken at extra high doses for special therapeutic benefit. Rather, for all its uses it should be taken in the amounts listed under Requirements/Sources, along with the recommended level of vitamin D (see the article on vitamin D for proper dosage amounts). Calcium absorption studies have found that your body can't absorb more than 500 mg of calcium at one time.11 Therefore, it is most efficient to take your total daily calcium in two or more doses. It isn't possible to put all the calcium you need in a single multivitamin/mineral tablet, so this is one supplement that should be taken on its own. Furthermore, calcium may interfere with the absorption of chromium and manganese.12,13,14 Although the calcium present in some antacids or supplements may alter the absorption of magnesium, this effect apparently has no significant influence on overall magnesium status.15,16 If you take any of these supplements, it is best to do so at a different time from when you take calcium. This means that it is best to take your multivitamin and mineral pill at a separate time from your calcium supplement. Calcium may also interfere with iron absorption,17–22 but you shouldn't take extra iron unless you know you are deficient. (For more information, see the article on iron.) Some studies show that calcium may decrease zinc absorption when the two are taken together as supplements; however, studies have found that, in the presence of meals, zinc levels may be unaffected by increases of either dietary or supplemental calcium.23–29 Corticosteroids cause osteoporosis by decreasing intestinal absorption of calcium as well as through other mechanisms. Supplementation with calcium and vitamin D may help prevent the loss of bone density associated with long-term corticosteroid therapy.30,31,32 Long-term or high-dose use of heparin might also cause osteoporosis, particularly in pregnant women. Again, supplemental calcium along with vitamin D may be helpful.33,34,35 Another drug that may interfere with calcium absorption is isoniazid, mostly because of its interaction with vitamin D.36,37,38 Finally, carbamazepine and other anticonvulsant drugs may impair calcium39,40 and vitamin D41–45 absorption and thereby interfere with bone formation and maintenance. Calcium and vitamin D supplementation may be helpful in avoiding these side effects. However, since calcium carbonate might interfere with the effects of anticonvulsant drugs, if you use that form of calcium, you should take it at least 2 hours apart from your anticonvulsant drug.46,47

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Therapeutic Uses

There is little doubt that calcium supplementation is useful in helping prevent and slow down osteoporosis.48–55 If you are a woman past menopause, this is true whether or not you are taking estrogen. Calcium supplements work best when combined with vitamin D. A new and rather surprising use of calcium came to light when a large, well-designed study found that calcium is an effective treatment for PMS (premenstrual syndrome).56 Calcium supplementation reduced all major symptoms, including headache, food cravings, moodiness, and fluid retention. There may be a connection between these two uses of calcium: it has been suggested that PMS might be an early sign of future osteoporosis.57,58 Some evidence suggests that getting enough calcium may reduce the risk of developing colon cancer and colon polyps, a precancerous condition.59 Individuals who are deficient in calcium may be at great risk of developing high blood pressure.60,61,126 Among individuals who already have hypertension, increased intake of calcium intake might slightly decrease blood pressure, according to some, but not all studies.62,127 However, taking extra calcium may not reduce blood pressure significantly.62 Calcium supplements might slightly improve cholesterol levels.63,64 One preliminary study suggests that supplementation with calcium and vitamin D may be helpful for women with polycystic ovary syndrome.65 Calcium supplementation has also been tried as a treatment to prevent preeclampsia in pregnant women. While the evidence from studies is conflicting,66,67,68 calcium supplementation might be effective in women with low calcium levels to begin with. Calcium also appears to offer the additional benefit of reducing blood levels of lead during pregnancy.69 The drug metformin, used for diabetes, interferes with the absorption of vitamin B12. Interestingly, calcium supplements may reverse this, allowing the B12 to be absorbed normally.70 Rapid weight loss in overweight postmenopausal women appears to accelerate osteoporosis slightly.71 For this reason, taking calcium and vitamin D supplements may be especially appropriate here. Interestingly, there is some evidence that calcium supplements might also facilitate weight loss to some extent, for reasons that aren't clear.72 One small but carefully conducted study suggests that making sure to get enough calcium may help control symptoms of menstrual pain.89 Finally, calcium is also sometimes recommended for attention deficit disorder, migraine headaches, and periodontal disease, but there is as yet little to no evidence that it is effective.

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What Is the Scientific Evidence for Calcium?

Osteoporosis

Numerous studies indicate that calcium supplements are useful in preventing and slowing osteoporosis, the progressive loss of bone mass as we age. Calcium supplementation at the recommended dosages appears to reduce bone loss in postmenopausal women in every part of the body except the spine.73,74,75 When vitamin D is taken along with calcium, it may be possible not only to slow down but actually reverse osteoporosis, in the spine as well as in other bones.76 However, calcium and vitamin D use must be continual. Improvements in bone rapidly disappear once the supplements are stopped.77 Calcium supplements, at least calcium-citrate malate, may do a better job of strengthening bones in individuals with relatively high protein intake.125 If you are taking estrogen to keep your bones strong, additional calcium will help it work better.78 Calcium supplementation is also useful for young girls as a way to "put calcium in the bank"—building up a supply for the future.79,80 However, exercise may be even more important.81 One study found that in calcium-deficient pregnant women, calcium supplements can improve the bones of their unborn children.82 Evidence suggests that the use of calcium combined with vitamin D can help protect against the bone loss caused by corticosteroid drugs such as prednisone. A review of five studies covering a total of 274 participants reported that calcium and vitamin D supplementation significantly prevented bone loss in corticosteroid-treated individuals.83 For example, in a 2-year double-blind, placebo-controlled study that followed 65 individuals with rheumatoid arthritis taking low-dose corticosteroids, daily supplementation with 1,000 mg of calcium and 500 IU of vitamin D reversed steroid-induced bone loss, causing a net bone gain.84 There is some evidence that essential fatty acids may enhance the effectiveness of calcium. In one study, 65 postmenopausal women were given calcium along with either placebo or a combination of omega-6 fatty acids (from evening primrose oil) and omega-3 fatty acids (from fish oil) for a period of 18 months. At the end of the study period, the group receiving essential fatty acids had higher bone density and fewer fractures than the placebo group.85 However, a 12-month double-blind trial of 42 postmenopausal women found no benefit.86 The explanation for the discrepancy may lie in the differences between the women studied. The first study involved women living in nursing homes, while the second studied healthier women living on their own. The latter group of women may have been better nourished, and already received enough essential fatty acids in their diet.

Premenstrual Syndrome (PMS)

According to a large and well-designed study published in a 1998 issue of American Journal of Obstetrics and Gynecology, calcium supplements are a simple and effective treatment for a wide variety of PMS symptoms.87In a double-blind, placebo-controlled study of 497 women, 1,200 mg daily of calcium as calcium carbonate reduced PMS symptoms by half over a period of three menstrual cycles. These symptoms included mood swings, headaches, food cravings, and bloating. These results corroborate earlier, smaller studies.88,89

High Cholesterol

In a 12-month study of 223 postmenopausal women, use of calcium citrate at a dose of 1 gram daily significantly improved the ratio of HDL (“good “) cholesterol levels to LDL (“bad”) cholesterol levels.124 This appears to have been primarily due to a meaningful rise in HDL levels.

Colon Cancer

Evidence suggests that the use of calcium carbonate can inhibit the development of precancerous polyps in the colon and rectum. A double-blind, placebo-controlled study followed 832 individuals with a history of polyps for 4 years.90 Participants received either 3 g daily of calcium carbonate or placebo. The calcium group experienced 24% fewer polyps overall than the placebo group. There is also evidence from observational studies that a high calcium intake is associated with a reduced incidence of colon cancer,91 but not all studies have found this association.92

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Safety Issues

In general, it's safe to take up to 2,500 mg of calcium daily, although this is more than you need.93,119 Greatly excessive intake of calcium can cause numerous side effects, including dangerous or painful deposits of calcium within the body. If you have cancer, hyperparathyroidism, or sarcoidosis, you should take calcium only under a physician's supervision. People with kidney stones or a history of kidney stones are also often warned not to take supplemental calcium. The reason for this caution is that kidney stones are commonly made of calcium oxalate crystals. However, studies have found that increased intake of calcium from food actually reduces the risk of kidney stones.94,95 Calcium supplements, on the other hand, might slightly increase kidney stone risk, especially if they are not taken with meals.96 The bottom line: avoiding calcium supplements may still be appropriate for certain people with a tendency to develop kidney stones.97 Ask your physician for advice specific to you. Large observational studies have found that higher intakes of calcium are associated with an increased risk of prostate cancer.98,99,100 This seems to be the case whether the calcium comes from milk or from calcium supplements. However, without further research it is difficult to tell whether this is a cause-and-effect relationship or simply an accidental correlation. Calcium supplements combined with high doses of vitamin D might interfere with some of the effects of calcium channel–blockers.101 It is very important that you consult your physician before trying this combination. Concerns have been raised that the aluminum in some antacids may not be good for you.102 There is some evidence that calcium citrate supplements might increase the absorption of aluminum;103–107 for this reason, it might not be a good idea to take calcium citrate at the same time of day as aluminum-containing antacids. Another option is to use different forms of calcium, or to avoid antacids containing aluminum. When taken over the long term, thiazide diuretics tend to increase levels of calcium in the body by decreasing the amount excreted by the body.108–111 It's not likely that this will cause a problem. Nonetheless, if you are using thiazide diuretics, you should consult with your physician on the proper doses of calcium and vitamin D for you. Finally, calcium may interfere with the absorption of antibiotics in the tetracycline and fluoroquinolone families as well as thyroid hormone.112–118 If you are taking any of these drugs, you should take your calcium supplements at least 2 hours before or after your medication dose.

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Interactions You Should Know About If you are taking

Corticosteroids , heparin, or isoniazid: You may need more calcium. Aluminum hydroxide : You should take calcium citrate at least 2 hours apart to avoid increasing aluminum absorption. The anticonvulsants phenytoin (Dilantin), carbamazepine, phenobarbital, or primidone: You may need more calcium; however, it may be advisable to take your dose of anticonvulsant and your calcium supplement at least 2 hours apart because each interferes with the other's absorption. Antibiotics in the tetracycline or fluoroquinolone (Cipro, Floxin, Noroxin) families, or thyroid hormone: You should take your calcium supplement at least 2 hours before or after your dose of medication, because calcium interferes with the absorption of these medications (and vice versa). Thiazide diuretics : Do not take extra calcium except on the advice of a physician. Calcium channel–blockers :Do not take calcium together with high-dose vitamin D except on the advice of a physician. Calcium: You may need extra iron, manganese, zinc, and chromium. Ideally, you should take calcium at a different time of day from these other minerals, because it may interfere with their absorption. Soy : A constituent of soy called phytic acid can interfere with the absorption of calcium, so it may be advisable to wait 2 hours after taking calcium supplements to eat soy (or vice versa). Metformin: Taking supplemental calcium may be helpful.

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References

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49. Dawson-Hughes B, Dallal GE, Krall EA, et al. A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women. N Engl J Med. 1990;323:878–883.

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63. Bell L, Halstenson CE, Halstenson CJ, et al. Cholesterol-lowering effects of calcium carbonate in patients with mild to moderate hypercholesterolemia. Arch Intern Med. 1992;152:2441–2444.

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73. Cumming RG. Calcium intake and bone mass: a quantitative review of the evidence. Calcif Tissue Int. 1990;47:194–201.

74. Dawson-Hughes B, Dallal GE, Krall EA, et al. A controlled trial of the effect of calcium supplementation on bone density in postmenopausal women. N Engl J Med. 1990;323:878–883.

75. Peacock M, Liu G, Carey M, et al. Effect of calcium or 25OH vitamin D3 dietary supplementation on bone loss at the hip in men and women over the age of 60. J Clin Endocrinol Metab. 2000;85:3011–3019.

76. Prince RL. Diet and the prevention of osteoporotic fractures [editorial]. N Engl J Med. 1997;337:701–702.

77. Dawson-Hughes B, Harris SS, Krall EA, et al. Effect of withdrawal of calcium and vitamin D supplements on bone mass in elderly men and women. Am J Clin Nutr. 2000;72:745–750.

78. Nieves JW, Komar L, Cosman F, et al. Calcium potentiates the effect of estrogen and calcitonin on bone mass: review and analysis. Am J Clin Nutr. 1998;67:18–24.

79. Lloyd T, Andon MB, Rollings N, et al. Calcium supplementation and bone mineral density in adolescent girls. JAMA. 1993;270:841–844.

80. Barr SI, Petit MA, Vigna YM, et al. Eating attitudes and habitual calcium intake in peripubertal girls are associated with initial bone mineral content and its change over 2 years. J Bone Miner Res. 2001;16:940–947.

81. Lloyd T, Chinchilli VM, Johnson-Rollings N, et al. Adult female hip bone density reflects teenage sports–exercise patterns but not teenage calcium intake. Pediatrics. 2000;106:40–44.

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83. Homik J, Suarez-Almazor ME, Shea B, et al. Calcium and vitamin D for corticosteroid-induced osteoporosis. Cochrane Database Syst Rev. 2000;(2):CD000952.

84. Buckley LM, Leib ES, Cartularo KS, et al. Calcium and vitamin D3 supplementation prevents bone loss in the spine secondary to low-dose corticosteroids in patients with rheumatoid arthritis. A randomized, double-blind, placebo-controlled trial. Ann Intern Med. 1996;125:961–968.

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87. Thys-Jacobs S, Starkey P, Bernstein D, et al. Calcium carbonate and the premenstrual syndrome: effects on premenstrual and menstrual symptoms. Premenstrual Syndrome Study Group. Am J Obstet Gynecol. 1998;179:444–452.

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