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Calcium

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Calcium Supplementation
The National Academy of Sciences and the National Osteoporosis Foundation recommend daily calcium intakes of 1000-1200 mg/day for adult men and women. According to experts, food is the best source of calcium; however, most Americans do not have enough calcium in their diets. Fortunately, calcium-fortified foods and calcium supplements can fill the gap, ensuring that the daily calcium requirement is met. The amount needed from a supplement depends on how much calcium is consumed from food sources.¹⁰

Some studies have shown that calcium supplements lower blood pressure in mildly hypertensive patients although the results are controversial. It is possible that calcium supplements can be mainly of benefit in cases where calcium intake is insufficient, which may be relatively common. Increasing calcium intake may increase the excretion of sodium thus reducing blood pressure.

Different calcium supplements contain different amounts of available calcium. Calcium carbonate and calcium citrate contain 40% calcium. Calcium gluconate and calcium lactate, the two most soluble forms contain 9% and 13% respectively. Bone meal and dolomite are common sources of calcium supplements but they may contain lead and cadmium which can be toxic. Antacids are also good sources of calcium but those containing aluminum or sodium should be avoided as aluminum inhibits calcium absorption and sodium can raise blood pressure.

Calcium citrate is an acidified form of calcium and is therefore absorbed better in older people who often have low stomach acid.

Calcium carbonate can be taken in divided doses with meals in order to avoid side effects such as nausea, gas and constipation. Absorption of calcium carbonate may be increased with food while other supplements may be best absorbed if taken between meals, as there may be some reduction in absorption due to the presence in food of certain fats and fiber.

Another form of calcium supplement, calcium hydroxyapatite is a naturally occurring calcium phosphorus protein bonded matrix of bone and is the actual protein calcium matrix found in bone. Calcium hydroxyapatite, which is found in bone meal, may actually restore bone.

Some calcium supplements can interfere with iron absorption. Iron and calcium supplements should be taken at different times although calcium citrate and calcium ascorbate may enhance iron absorption, as they are acidic.

When taken with magnesium supplements, the ratio should be 2:1 calcium to magnesium.  Also see: Coral Calcium

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Calcium Interactions and Contraindications
Calcium is regulated by several things: vitamin D, which helps the body absorb calcium and deposit it in the bones, calcitonin, which enhances the ability of the bones to store calcium by transferring calcium from the blood to the bones and inhibiting release, parathyroid hormone, which regulates the transfer of calcium from the bones to the blood, oestrogens which help retain calcium in the bones, and thyroid and growth hormones.

In the absence of vitamin D, less than 10% of dietary calcium may be absorbed.^3,4

Lead absorption is blocked by calcium in the intestines. Boron supplementation may reduce the excretion of calcium. Aluminum containing antacids can inhibit calcium absorption. Excessive calcium can interfere with the absorption of copper, iron, magnesium, manganese and zinc.³

Calcium and magnesium and calcium and potassium are related in that high levels of one can produce low levels of the other. Excessive potassium can lower calcium levels. Calcium and phosphorus work together to form healthy bones and teeth. If your phosphorus intake is too high your body excretes the extra and calcium along with it.^3,4 Large quantities of sucrose can enhance calcium excretion. Sugars and phosphoric acid are primary ingredients in soft drinks.

Large quantities of fat, oxalic acid, (which is found in chocolate and rhubarb) and phytic acid, which is found in grains can prevent calcium absorption.

The contraceptive pill, anti-epileptic drugs, diuretic drugs, corticosteroid drugs for rheumatoid arthritis, asthma and IBD, and some antidepressants can lead to calcium deficiency. Calcium deficiency can also be caused by smoking, malabsorption due to lactose intolerance and absorption disorders such as coeliac disease.

Calcium decreases the absorption of tetracycline antibiotics, iron and aspirin if taken at the same time.

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Cautions
You should not take calcium supplements if you have impaired kidney function or a history of kidney or bladder stones, or if you suffer from constipation. Controversy exists over whether low or high calcium intakes increase urinary excretion and may increase the chance of forming kidney stones. ^8,13,14

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References

1. Smith L, "Breathing Easy" Feed Your Kids Right. 1979 Dell Pub. Co. Inc.
2. Whitney EN, Rolfes SR. Water and the Major Minerals. In: Understanding Nutrition. Seventh Edition, St. Paul, MN: West Publishing Company; 1996; 448-454.
3. Somer E. Minerals. In: The Essential Guide to Vitamins and Minerals, New York, NY Harper Perennial: New; 1995; 89-94.
4. Van Fleet J. "How a mineral can vitalize your health", Magic of Catalytic Health Vitalizers, 1980, Parker Publishing.
5. Linas RR, "Calcium in Synaptic Transmission", Scientific American, October, 1982.
6. Bucher HC, Cook RJ, Guyatt GH, et al. Effects of dietary calcium supplementation on blood pressure. Calcium meta-analysis of randomized controlled trials. JAMA 1996;275:1016-22.
7. Mundy GR, "Calcium, Homeostatis: Hypercalcemia and Hypocalcemia", Professor and Head, Division of Endocrinology and Metabolism, University of Texas.
8. Barefoot RM, Reich CJ; The Calcium Factor; 1992: Bokar Consultants, Wickenburg, AZ
9. McCarron K, Reusser M. 1991. "The integrated effects of electrolytes on blood pressure." Nutr Rep 9:57,62,64.
10. Krook L, et al. Human periodontal disease. Morphology and response calcium therapy. Cornell Vet 1972;62:32-53.
11. Gregor JL. "Effect of variations in dietary protein, phosphorous, electrolytes and vitamin D on calcium and zinc metabolism." In CE Bodwell and JW Erdman, Jr., eds. Nutrient Interactions. New York, NYMarcel Dekker, Inc; 1988.
12. Swope MR. "The Greenleaves of Barley", 1987; Swope Enterprises, Inc. Phoenix, AZ
13. Villar J and Repke JT. Calcium supplementation during pregnancy may reduce preterm delivery in high-risk populations. Am J Obstet Gynecol 1990;163: 1124-31.
14. Penland JG, Johnson PE. Dietary calcium and manganese effects on menstrual cycle symptoms. Am J Obstet Gynecol 1993;168:1417-23.
15. Marshall RW, Cochran M, Hodkginson A. Relationship between calcium and oxalic acid intake in the diet and their excretion in the urine of normal and renal-stone forming subjects. Clin Sci 1972;43:91-9.
16. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A Prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med 1993;328:833-8.
17. Lips P, Graafmans WC, Ooms ME, et al. Vitamin D supplementation and fracture incidence in elderly persons. Ann Intern Med 1996; 124: 400-6.

Venter JC, Tiggle D, Structure and Physiology of the Slow Inward Calcium Channel, 1987, Alan R Liss. Inc.

The Role of Calcium in the Biological System, 1985, CRC Press, Inc.

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Also See: Coral Calcium