Calcium Citrate vs Calcium Carbonate

Summary: The differences between Calcium Citrate and Calcium Carbonate aren’t as great as manufacturers would like you to believe. Elemental calcium absorption is the same no matter which salt form of calcium you take. What does effect calcium absorption is your Vitamin D status and whether or not the tablet you are taking is actually dissolving.

Dear Curtis: My doctor told me it would be a good idea to start a calcium supplement. But there’s so much on the shelf I’m not sure what to choose. It seems like the two most popular types are calcium carbonate and the calcium citrate. I’ve heard that calcium citrate is suppose to be better quality but the carbonate one is so much cheaper. Is the price difference worth it?

A couple of things to tackle in your question.

First of all, there are differences in the types of calcium you are talking about. Which I’ll get to in a moment. But when someone tells me that they need a calcium supplement one of the first things I tell them is that while you need calcium for a lot of functions in your body it’s important for you to understand that having strong, healthy bones goes well beyond just popping a calcium tablet.

For example, a lot of folks don’t realize that you need ample amounts of Vitamin D for calcium to be absorbed at all. Of course, the majority of Vitamin D comes from the sun. And, as you probably already know most people in this country simply don’t get enough Vitamin D. The point being: taking all the calcium in the world won’t help the problem unless it can be absorbed and you need Vitamin D for that to happen.

Chemical Differences Between Calcium Forms

With that being said, let’s assume that supplementing with calcium is definitely needed.

First of all, for calcium absorption to occur (which happens in your gastrointestinal tract) it has to be in it’s ionized – or most basic, elemental form.

As you already mentioned you are looking at two forms of calcium: calcium carbonate and calcium citrate. All these names mean is that they are the ‘salt’ forms of calcium. Again, what we are really concerned about is the elemental amount of calcium in each tablet.

For calcium carbonate roughly 40% of each mg is elemental calcium. So, for the 500mg Tums tablet you are consuming 200 mg of elemental calcium. Surprisingly, calcium citrate is only 21% elemental calcium. With the popular brand name Citracal that means you are getting 315 mg of elemental calcium per tablet (and be careful when reading the label of Citracal because they use calcium per serving – which is actually two tablets, not one).

Dissolution: The Key to Absorption

One thing that is never discussed is dissolution. Which, in plain terms, means is the tablet dissolved? In short, you can’t absorb the calcium in the tablet you are taking if the tablet doesn’t dissolve.

Frankly, this is one of the reasons I recommend to folks to avoid calcium tablets and instead go for a chewable form of calcium (like you can chew Tums and Calci-Chew).

While this last statement may make it seem like calcium carbonate is a no brainer – the manufacturers of Citracal included Vitamin D in their supplement. Which, as I mentioned above, is required for calcium to actually be absorbed.

Absorption Is the Same

One of the confusing things is that manufacturers claim that their particular product has more absorption than another. But the simple fact of the matter is that when you can get elemental calcium into your system roughly 25% to 35% of it is actually absorbed in your body. Of course, this is with all things being equal.

And that’s where the tough part comes in for you. Everything is NOT equal. How is your Vitamin D status? You should know that. If that is sound then taking a chewable form of calcium carbonate would likely work just fine and you shouldn’t need the extra Vitamin D is products like Citracal.

Are you taking medications that lower your stomach acid? If so, you’ll want to go for a product like Citracal because it doesn’t require food for absorption whereas calcium carbonate’s absorption is helped by taking it with meals because you are producing more stomach acid.

My biggest piece of advice is that there really aren’t as many differences between calcium carbonate and calcium citrate as the manufacturers would like you to believe. As far as bang for the buck I think you’ll always be ahead with the chewable form of calcium carbonate. I have concerns about any compressed tablet form of calcium because they have a tendency not to dissolve.

But again, irregardless of what form of calcium you choose, the biggest factor is absorption and you need a solid Vitamin D status to actually absorb the calcium you take.