The Health Sciences Institute is intended to provide cutting-edge health information.
Nothing on this site should be interpreted as personal medical advice. Always consult with your doctor before changing anything related to your healthcare.

Types of calcium supplements

Absorbing it All

If you take a daily calcium supplement to support bone health, the type of calcium you’re taking could make a big difference.

In the e-Alert “Attack of the Vapors” (1/6/04) I collected comments about vitamin C that HSI Panelist Allan Spreen, M.D., has shared with us over the years. A member named Laz responded to that e-Alert with this question: “That was a very concise explanation of vitamin C. Now could you do the same with the different calciums?”

Sure can, Laz. I asked Dr. Spreen to fill us in on the calcium types, and his response will be an eye-opener for anyone who believes the advertisements that tell you antacid tablets are a good source of calcium, or for anyone who doesn’t understand that the milligrams you take are not necessarily the milligrams your body absorbs.

The lineup

The question of, “What’s a good calcium?” is actually somewhat complicated. But a simple place to start is by recognizing that all calcium types are either organic or inorganic salts.

The inorganic forms:

  • Calcium sulfate
  • Calcium phosphate
  • Calcium carbonate

The organic forms:

  • Calcium gluconate
  • Calcium lactate
  • Calcium citrate
  • Calcium amino acid chelate (there are several of these)
  • Calcium orotate
  • Calcium aspartate
  • Calcium ascorbate

And here I’ll turn things over to Dr. Spreen: “Each of the above is obviously not entirely calcium there’s a percentage of ‘the other stuff’ attached to the molecule. So, the percentage of the compound that’s ‘elemental calcium’ is an issue.

“The most common form of supplement, by far (of all types), is calcium carbonate. It’s also the cheapest. What’s more, it also has the most elemental calcium (40% of the total molecule). Seems like that might pretty much settle the selection issue, right? Unfortunately, there are two problems with the carbonate form: 1) Like the other inorganic forms, it’s the most poorly absorbed (only 5-10%); and 2) Unlike the other inorganic forms, calcium carbonate requires (and binds) the most acid.

“The latter problem above is appealing if you’re trying to sell an antacid product ‘that’s also good for your bones,’ but it’s very much a double-edged sword. More acid is now required for the digestion of proteins, or else malabsorption (and indigestion!) can occur. Since you take the antacid for indigestion, you can see where this is headed.”

The good stuff

The obvious answer to the absorbency problem with the inorganic forms is to choose one of the organic forms where absorption can run anywhere from 25 percent to as high as 95 percent. But again, the details complicate the matter.

Dr. Spreen says that the best absorbed of the commercially available types are calcium orotate (90 to 95 percent absorbed), closely followed by calcium aspartate (85 percent absorbed). However, he points out that, “these are not only the most expensive, but they’re also the hardest to find. That means they may not be an option for many people.

“Another really good one is calcium ascorbate, which gets you the benefit of vitamin C as the other part of the molecule, along with the fact that it’s no longer an acidic form of vitamin C a neat solution to several problems. Again, however, it’s both expensive, and difficult to find in many places.

“My next choice would be any of the amino acid chelates, at 65-80 percent absorption, but these are still fairly expensive, and not as easily found (though easier than the preceding two). These are probably the best compromise if you’re willing to spend just a bit more.”

Dr. Spreen notes that the best compromise of price, percentage of elemental calcium, and absorption would probably be calcium citrate. The absorption is 30 to 35 percent, and the citric acid reduces the amount of stomach acids required for absorption. For most people, calcium citrate would be the most reasonable way to go.

Bringing more to the table

But now that we’ve found an effective and economical calcium, we’re not quite out of the woods. The problem is that you can’t take calcium alone without making biochemical trouble for the body. Here’s how Dr. Spreen explained it to me:

“Calcium is not found in nature (in edible form) without magnesium, and they therefore should always be given together. Studies show that calcium alone may even be preferentially laid down in arterial walls rather than in bones (that doesn’t sound good, does it?). Plus, phosphorous is also needed with calcium. The problem here is that phosphorous is one of the few minerals that’s over-supplied in the modern (trash) diet. Excesses of phosphorous in the absence of the other minerals can create a problem with balance and possible leaching of other minerals.

“What’s not mentioned in those cute major-media ads for calcium and antacids is that for bones, the calcium must also have not only magnesium (okay, and phosphorous), but also manganese, silica, boron, strontium, and vitamin D (and that last one in high doses), vitamin C, vitamin B-12, and probably even more.

“And you might even have an issue with higher quality supplements. The really good companies will state on the label something like ‘elemental calcium, in the form of ‘ and tell you how many milligrams of the real thing you’re getting (though absorption is of course still an issue).

“Unfortunately, some labels will state something like, ‘Calcium gluconate, 1000 mg.’ Are you getting 1000 milligrams of calcium? Nope, in fact you’re getting 93 milligrams of calcium; what you got was 1000 milligrams of the entire compound.

“I wish there were an easy answer. Fortunately, most calcium supplements are not expensive, so you can take a lot of one that isn’t that well absorbed and do okay, as long as you’re getting a multi-mineral supplement that has some of the other minerals in there (minus iron, but that’s a story for another day). Read those labels carefully, and Caveat Emptor!”

Food boost

One obvious way to support the effectiveness of calcium supplements is to make sure you include plenty of calcium- rich foods in your diet, such as cabbage, kale, yellow, green, or waxed beans, and salmon. Foods that are high in magnesium include leafy green vegetables, whole grains, bananas, apricots, meat, beans, and nuts.

My thanks to Dr. Spreen for his informative look at calcium. If you have further questions about calcium – or any other nutrition topic – pass them along and I’ll ask Dr. Spreen to reply.