Posted on: September 25, 2025
Calcium is the most abundant mineral in the body. It makes up 1.5 to 2 percent of the total boy weight, and the bones contain more than 99 percent of the body’s calcium. In addition to it’s major function in building and maintaining bone and teeth, calcium is important in much of the body’s enzymatic activity. The contraction of muscles, release of neurotransmitters, regulation of heartbeat, and clotting of blood all also depend on calcium.
The best way to get calcium is through food, however the North American diet doesn’t supply enough. Calcium is present in many plants and fortified foods. Green vegetables such as bok choy, broccoli, Chinese or Nappa cabbage, collards, kale, okra, and turnip greens provide calcium with high bioavailabillity. Bioavailabillity indicates the percentage of the ingested mineral absorbed into the body and into cells. 49-61 percent of the calcium in these foods is absorbed through a normally functioning digestive system. Calcium in other foods, such as tofu, fortified fruit juices and cow’s milk is 31-32% absorbed, while only 21-24% of calcium eaten in foods such as fortified soymilk, sesame seeds, almonds, and red and white beans is absorbed.
These issues of absorption also factor into calcium supplements. This is why some calcium costs $6 for a 60 pill bottle and other forms of calcium can cost as much as $40 per bottle or more.
The most popular and cheapest form of calcium supplement is Calcium Carbonate. This form of calcium comes from oyster shells, bone meal or dolomite, or can be derived from limestone in a laboratory. Calcium Carbonate coming from the first three sources, oyster shells, bone meal or dolomite is labeled as “natural” or “unrefined”. Studies have shown that theses forms of calcium contain high amounts of lead. “Refined” forms of calcium carbonate, that is the ones made in the laboratory from limestone, contain very little lead and are the safest. About 22 percent of calcium from oral calcium carbonate is absorbed by a person with healthy digestion, while only 4 percent of calcium will be absorbed by patients with low stomach acid.
“Coral Calcium” is another form of calcium supplement that has been heavily marketed recently. Marketers point out that coral calcium is in a 2:1 ratio with magnesium, that is for every two molecules of calcium there is one molecule of magnesium. This ratio increases absorption and helps with all the functions in the body. They also point out that there are anywhere from 65 to 75 other minerals in coral calcium that are essential for humans. While these things are true, the amounts of the other essential minerals are very small, and found in much greater amounts in foods and vitamin-mineral supplements. The 2:1 calcium to magnesium ratio is also often found in other much less expensive calcium supplements. While calcium carbonate supplements retail for $6-10 per bottle, coral calcium can retail for as much as $50 for the same amount. Simply, the extra minerals found in coral as a source of calcium do not justify its cost.
Another form of calcium supplement is calcium combined to biologically active molecules, such as citrate, gluconate, or lactate. Combining with these molecules makes calcium much more easily absorbed, allowing for 45 percent absorption in patients with weak digestion. Remember that calcium carbonate was only absorbed at a rate of 4 percent by this group. Because this form of calcium is synthesized in a laboratory, it contains very low levels of lead, and is a little bit more expensive than calcium carbonate. It retails for about $10-20 per bottle.
So, with all these different forms of calcium available, which is the best to take? In short, it is best to get your calcium from eating a whole foods diet, rich in green leafy vegeteables listed above. If this is not possible, and absorption is not an huge issue, refined calcium carbonate at 1000 mg per day with 200 to 400 IU Vitamin D and 300 to 400 mg Magnesium is a good way to go. For someone with weak digestion, a pricier but more absorbable form of calcium, such as calcium citrate or calcium malate is recommended. Inappropriate use of calcium can lead to kidney stones and soft tissue calcification, thus as always, before self-diagnosing and self-medicating, a visit to your friendly local Naturopathic Doctor is recommended.
Submitted for publication in Zdrowy Styl Health Magazine, 2004