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Calcium
by author Graham Butler BSc, RNCP

If you’re anything like the average consumer, you’re likely confused by the dizzying array of calcium supplements on the market. Colourful bottles of capsules, tablets, or liquids in dozens of formulations–how to choose?

Your Body’s Calcium Budget

The absorption of calcium follows two principle pathways: through active transport in the upper small intestine (which is limited to 225 mg to 450 mg at any one time and is dependant on vitamin D), or by passive diffusion throughout the small intestine. Diffusion is affected mainly by the speed of digestion - the slower the digestive process, the higher the absorption. Certain foods inhibit uptake to some extent, specifically the phytates found in grains.

Absorption isn’t the end of the story though. The parathyroid gland (active when we sleep), along with the assistance of vitamin D, regulates the amount of calcium in extra cellular fluid (ECF), the mineral-rich fluid between our cells. This is critical to neuromuscular activity, the heart, as well as a broad range of enzyme-mediated reactions.

Bone is the chief repository of calcium in the body. In times of calcium deficiency it acts as a reservoir for the body to draw on to balance ECF calcium levels. Long-term calcium deficiencies may result in the breakdown and reabsorption of bone matrix by the body, e.g., osteoporosis. Normal estrogen levels in premenopausal women offer protection against this.

A research study “Magnesium Supplementation and Osteoporosis” published in Nutrition Review in 1995 found that magnesium supplementation increases bone density up to eight percent on its own and up to 11 percent when combined with calcium and cofactors such as vitamin C, vitamin B complex, zinc, copper, manganese, and silica and boron.

In addition, a research study undertaken by Dr. Wolfgang Kemmler and associates, and reported in the Archives of Internal Medicine in 2004, found that exercise - particularly weight-bearing exercise–significantly increases bone density.

Curbing Calcium Excretion

The major factor that increases calcium excretion (the loss of calcium through the kidneys, urine, and perspiration) is animal protein intake. People in western countries tend to have high levels of animal protein intake with correspondingly high recommended daily intakes for calcium and high rates of osteoporosis. According to the Osteoporosis Society of Canada, in addition to animal protein, excessive consumption of caffeine, sodium, phosphoric acid, and sugar contribute to calcium excretion.

Dietary Sources of Calcium

Although dairy products are often marketed as a good source of calcium, countries with high dairy consumption (a major source of animal protein) have the highest daily calcium intakes as well as the highest rates of osteoporosis. Other alternative sources of calcium include salmon, sardines, kale, cabbage, broccoli, almonds, asparagus, tofu, and dark green vegetables.

Calcium Supplements

There are a number of common forms of calcium available, the most common being calcium carbonate, various types of chelated calcium including calcium citrate, as well as calcium gluconate and calcium lactate. Calcium carbonate is available in tablet and capsule form and liquid suspensions. Absorption is through active transport and is dependent on sufficient hydrochloric acid (HCL) concentrations in the stomach as well as the presence of vitamin D. Calcium carbonate supplements should be taken with food. As HCL levels tend to decline with age, so does calcium carbonate absorption.

Calcium citrate is absorbed better than calcium carbonate and is not dependent on HCL. Available as tablets, capsules, and liquid suspensions and solutions, all but the latter are absorbed through active transport. Calcium citrate solutions are absorbed by both active transport and diffusion, and are not dependent on digestive factors. Calcium gluconate and lactate liquid solutions are absorbed in a similar manner and at the same degree as calcium citrate solutions.

Calcium citrate, gluconate, or lactate in solution taken after the evening’s meal slows digestion and suppresses the parathyroid’s effect on bone. For those who don’t take to liquids, calcium citrate in tablets or capsules is fine.

Used in conjunction with magnesium, B vitamins, vitamin C, zinc, manganese, silica and boron, and calcium will enhance bone regeneration.

Recommended Dietary Calcium Intake

Ages 4 to 8 - 800 mg
Ages 9 to 18 - 1,300 mg
Ages 19 to 50 - 1,000 mg
Ages 50 and older - 1,500 mg
Pregnant or lactating - 1,000 mg

Source: Osteoporosis Society of Canada (osteoporosis.ca).

Graham Butler BSc, RNCP, is a writer, researcher, and consultant to the natural products industry.

Source: alive #271, May 2005

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