Supplements

Calcium

There is more calcium in the body than any other mineral. Calcium is critical to the development and maintenance of bones and teeth.

It also plays an important role in controlling the heartbeat, maintaining proper blood pressure, clotting blood, transmitting nerve impulses, contracting and relaxing muscles, maintaining the integrity of mucosal membranes and cell walls, and activating enzymes such as lipase, adenosine triphosphatase (ATPase), succinate dehydrogenase, and choline acetylase.

Consuming less than 500 mg a day of calcium, greatly multiplies the chance of bone deterioration. Some studies conclude that simply taking calcium tablets (1,500 mg per day is an often mentioned dosage) contributes to bone strength and is a good hedge against postmenopausal bone loss (one reviewer concluded it slows menopausal bone loss by 30-50 percent), other research asserts that supplements reinforce bone density only if combined with regular weight-bearing exercise.

Bone sturdiness depends upon a sufficient supply of other nutrients - vitamin D, magnesium, copper, zinc, manganese, boron, and vitamin C.

When the amount of magnesium in the bloodstream falls, the kidneys readjust the balance by holding on to less calcium. When magnesium's concentration rises, the kidneys excrete less calcium.

20 percent of an adult's bone calcium is reabsorbed and replaced every year.

In order for calcium to be absorbed, the body must have sufficient vitamin D.

Calcium and magnesium work together for cardiovascular health. In a review of twenty-five clinical trials involving hypertensives, twelve showed that the mineral could cut the risk of high blood pressure, and twelve did not. The chance of preeclampsia, the pregnancy-related hypertension disorder, was similarly reduced.

Calcium supplementation may guard against cancers of the endometrium, pancreas, and colon. With a daily dose of 1,250 mg of calcium carbonate, the proliferation of colonic epithelial cells decreases. Another study of 1,900 men found that 1,200 mg per day reduced the incidence of colon cancer by 75 percent.

Although kidney stones can result from toxic levels of calcium in certain susceptible individuals, high calcium intake can actually decrease the risk of kidney stones, and large calcium supplements are accepted therapy for kidneys stones associated with intestinal hyperoxalosis.

Calcium is a very potent sleep inducer. Taking supplements at bedtime may produce a bonus benefit for a better night's sleep.

Calcium hydroxyapatite and calcium citrate are the most readily absorbed supplemental forms of calcium.

Deficiency: Calcium deficiency can lead to the following problems: aching joints, brittle nails, eczema, elevated blood cholesterol, heart palpitations, hypertension insomnia, muscle cramps, nervousness, numbness in the arms and/or legs, a pasty complexion, rheumatoid arthritis, rickets, and tooth decay. Cognitive impairment, convulsions, depression, delusions and hyperactivity are also associated with calcium deficiency.

Depleting Agents: Large quantities of fat, oxalic acid (found in chocolate, spinach, Swiss chard, parsley, beet greens, and rhubarb), and phytic acid (found in grains) are capable of preventing proper calcium absorption. A diet high in sugars, grains, and other carbohydrates weakens bones. When a group of women began to eat foods higher in carbohydrates, they lost bone density. Sugar acidifies the blood, forcing calcium out of the body.

Sources: Calcium is found in dairy foods, salmon (with bones) sardines, seafood, and dark green leafy vegetables. Additional food sources are almonds, asparagus, blackstrap molasses, brewer's yeast, broccoli, buttermilk, cabbage, carob, cheese, collards, dandelion greens, dulse, figs, filberts, goat's milk, kale, kelp, milk, mustard greens, oats, prunes, sesame seeds, soybeans, tofu, turnip greens, watercress, whey, and yogurt.

Herb Sources: burdock root, cayenne, chamomile, chickweed, chicory, dandelion, eyebright, fennel seed, fenugreek, flaxseed, hops, horsetail, kelp, lemongrass, mullein, nettle, oat straw, paprika, parsley, peppermint, plantain, raspberry leaves, red clover, rose hips, shepherd's purse, violet leaves, yarrow, and yellow dock.

Dosage Ranges and Duration of Administration: Recommendations for adequate calcium intakes promulgated by the National Academy of Science Food and Nutrition Board in 1997:

Infants:

• birth to 6 months: 210 mg/day
• 6 months to 1 year: 270 mg/day

Children:

• 1 to 5 years: 500 mg/day
• 6 to 8 years: 800 mg/day

Adolescents:

• 9 to 18 years: 1,300 mg/day

Adults:

• 19 to 50 years: 1,000 mg/day
• Over 50 years: 1,200 mg/day

Lactating or pregnant women:

• 14 to 18 years: 1,300 mg/day
• 19 years and older: 1,000 mg/day

INTERACTIONS

Alendronate
Because calcium supplements may interfere with alendronate absorption, they should be taken two hours before or after the drug.

Aluminum Hydroxide
In a study with eight male subjects, 5 mL of aluminum hydroxide gel (2.4 gm qid) coadministered with calcium citrate (950 mg qid) for three days increased urinary aluminum excretion. The finding of enhanced aluminum excretion is consistent with another study involving 30 healthy women who were given calcium citrate (800 mg elemental calcium/day). Urinary and plasma aluminum levels were increased significantly. This effect may have been related to aluminum derived only from dietary sources because the women were not receiving aluminum-based antacids.

Amiloride
Two doses of amiloride (2.5 mg/day) reduced urinary calcium in subjects with kidney stones. This decrease in calciuresis was enhanced when amiloride was coadministered with two doses of hydrochlorothiazide (25 mg/day).

Atenolol
Oral administration of 500 mg calcium salts (lactate, gluconate, and carbonate) with atenolol (100 mg) reduced plasma levels of atenolol by 51% in six healthy subjects. Long-term coadministration increased the elimination half-life and led to atenolol accumulation. Subsequent studies did not confirm an interaction between atenolol and calcium antacids. Until more is known, individuals on beta-blockers should have their blood pressure checked before and after the addition of calcium antacids or supplements to their atenolol regimen.

Digoxin
Hypocalcemia can negate the therapeutic effects of digoxin, while hypercalcemia may predispose a patient to arrhythmias and digoxin toxicity. In one study, patients with digoxin-induced cardiotoxicity had serum concentrations of the drug that were within therapeutic range but they had higher calcium to potassium ratios. Normal levels of calcium should be maintained during digoxin treatment. Patients taking digoxin should have calcium blood levels monitored closely.

Estrogens; Progestins
Conjugated estrogens lower calcium excretion and increase calcium absorption in postmenopausal women. The enhanced absorption appears to be due to an increase in serum 1,25(OH)2D. Early postmenopausal women taking calcium supplements with estradiol (or conjugated estrogens) have been shown to have significantly greater gains in bone mineral density than women taking HRT alone. Calcium supplementation is highly recommended in all postmenopausal women. For women 51 years or older, the Dietary Reference Intake (DRI) for calcium is 1200 mg/day.

Gentamicin
In a retrospective study, coronary artery bypass graft patients who received both a bypass prime with a high calcium concentration and gentamicin perioperatively had a higher incidence of renal failure compared with those who received only the prime, gentamicin alone, or neither. Concomitant administration of calcium may potentiate gentamicin-induced nephrotoxicity.

Quinolone Antibiotics
Quinolone antibiotics form chelates with metal cations, such as aluminum, magnesium, calcium, iron, zinc, copper, and manganese, which significantly reduces the absorption of these medications. Dietary supplements and antacids containing aluminum and magnesium should be taken two to four hours before or after administration of these antibiotics.

Tetracycline Derivatives
Tetracyclines form chelates with divalent and trivalent cations, including iron, aluminum, magnesium, and calcium. These chelates are poorly soluble and can significantly reduce the absorption and efficacy of tetracyclines. Calcium salts should be administered at least two hours before or after tetracyclines.

Thiazide Diuretics
Thiazide diuretics may cause hypercalcemia by decreasing calcium excretion. Treatment with a combination of hydrochlorothiazide (50 mg/day) and vitamin D in six postmenopausal women with osteoporosis for six months reduced urinary calcium excretion by 22%.41 In this study, it was noted that the combination of hydrochlorothiazide and vitamin D also decreased calcium absorption by 25%. However, the ability of thiazide diuretics to decrease urinary calcium excretion has been associated with less risk of hip fractures in patients taking these medications.

Verapamil
It has been reported that calcium salts may reverse the clinical effects and toxicities associated with verapamil. However, pretreatment with intravenous calcium in patients with supraventricular arrhythmias reduced the incidence of hypotensive side effects without compromising the antiarrhythmic effect of verapamil. Calcium also influenced blood pressure by restoring it to control values when administered after treatment with verapamil.