Types of Calcium Used in Food Supplements

Finding the right calcium supplement for you can be tough. Never mind the hundreds or thousands of brands to sort through, but all the different types of calcium, too! Well, you’re about to discover how to make the decision far easier. You may even learn some things you didn’t know that could change your relationship with calcium!

Let’s start by quickly discussing 10 of the most common types of calcium. Before we list them and offer the pros and cons of each, you should know about elemental calcium.

You’ll never find calcium all on its own in nature. Instead, it exists in compounds, which is a combination of elements. These calcium compounds are called “calcium salts,” even though they don’t contain any salt. And one of the most common calcium salts is calcium carbonate, which is found in rocks like marble and limestone.

Calcium carbonate contains elemental calcium bonded with elemental carbon and elemental oxygen. When you consume calcium carbonate, these elements break away from one another, and you get pure calcium.

This pure calcium is referred to as elemental calcium. In the case of calcium carbonate, you get 40% elemental calcium. That means for every 500 mg of calcium carbonate, 200 of those milligrams is actual calcium. [1]

It’s important to be aware of the elemental value of each calcium type. But it’s not the be-all, end-all. In the United States and Canada, the labeling laws require the manufacturer to list the elemental calcium on the label, so no need to bring your calculator. If the calcium carbonate label says “400 mg,” it means you’re getting 400 mg of elemental calcium.

Now, let’s jump into 10 of the most common types of calcium used in supplements. You’ll see how much elemental calcium they have and where they come from.

As you can see, many types of calcium are derived from marble or limestone and are bound with some form of acid.

Let’s take calcium citrate as an example. Calcium citrate isn’t a natural form of calcium, it’s just a calcium compound (calcium carbonate) bound with citric acid. These other calcium compounds can offer different benefits, but the real source of the calcium is still rock, which the human body wasn’t designed to consume.

Now, let’s dive into the 10 most common types of calcium, in descending order of elemental calcium.  

Calcium carbonate is cheap to source, so it’s very common. It’s normally blasted out of limestone and marble quarries. But it’s also found in other sources, too.

Maybe you’ve heard of “eggshell calcium”? People crush eggshells into a powder to make a homemade calcium supplement. But it’s still calcium carbonate! In fact, a lot of other calcium types are actually a modified version of calcium carbonate.

Calcium phosphate is the calcium salt of phosphoric acid. It’s the primary form of calcium in cow’s milk. You may also see calcium phosphate in your toothpaste, too! See, the primary mineral of tooth enamel is calcium phosphate, and one study on extracted human teeth suggests calcium phosphate-based toothpaste supports tooth enamel.

When it comes to calcium supplements, you’ll commonly find calcium phosphate as tricalcium phosphate or microcrystalline hydroxyapatite (MCHC — we’ll cover this in just a moment.) Tricalcium phosphate supplements tend to source their calcium from rocks with a high concentration of phosphate. And remember, your body isn’t designed to digest rock.

Just as the name says, this is calcium from plants. You should know, there’s no such thing as “plant calcium.” The calcium salts found in plants are the same as the ones found in rocks, but there are reasons why plants are a preferable source of calcium.

You see, plant-based sources of calcium offer a natural matrix of bone-building nutrients along with the calcium.

Read more: Check out our “Top Calcium-Rich Foods” page for the top plant and animal sources.

Each nutrient can support healthy bones on its own, but many of them have another specialty: They help your body better absorb calcium!

This avoids the common gastrointestinal issues that accompany rock-based calcium as well as other serious health concerns that can arise from rock calcium use. [2]  Calcium from rocks tends to deposit in soft tissues like arteries, kidneys, and muscles, since it’s missing the other nutrients that transport calcium into your bones.

So, how do you know which plant sources of calcium to take? Well, there’s one special source of red marine algae called Lithothamnion superpositum. AlgaeCal has four calcium compounds plus 13 minerals essential for building bone in the optimal balance for humans. The calcium and other nutrients are metabolized by the algae, meaning they’re “pre-approved” to get to work in your body without causing any nasty side-effects.

Lithothamnion superpositum has actually been used in human studies. And it’s accomplished something no calcium supplement ever has: increased bone mineral density in older adults.[3]

Hydroxyapatite is a mineral complex derived from cow bones. In hydroxyapatite, calcium is bound with phosphorus. (This is the principal form of calcium storage in bone.) That sounds great for bone health, but there’s a catch.

When you consume calcium, the calcium is freed from whatever substance it’s bound with. So in the case of hydroxyapatite, the calcium is separated from the phosphorus before either is absorbed. Unfortunately, this means you absorb more phosphorus than you ideally should.

Research shows too much dietary phosphorus can be a risk factor for cardiovascular and kidney diseases. What’s more, one study found the risk of fractures increased by 9% for every 100 mg of phosphorus intake.[4]

That’s concerning, especially as the general population is already consuming more than enough phosphorus in processed foods and food additives.

Calcium citrate is another of the more common calcium types used in calcium supplements. It’s derived from rock calcium bound with citric acid (think citrus juices, especially lime and lemon).

Calcium citrate has an acidic base, so it doesn’t require hydrochloric acid for absorption. This means calcium citrate is particularly beneficial for people taking certain medications that reduce stomach acid, or people that have had gastric bypass surgery. And because you don’t need stomach acid to consume calcium citrate, you can take it with or without food.

It may sound a lot like calcium citrate, but calcium citrate malate is a little different. Calcium citrate malate contains the calcium salt of citric acid and malic acid, and was first patented in the late 1980s. It’s a water-soluble calcium, which means it dissolves without the need for stomach acid. That means you can take it with or without food.

And if you’ve ever seen fruit juices and other drinks that say they’re “calcium-fortified” on the label, the added calcium is often calcium citrate malate.

Calcium lactate is a salt that consists of two lactate anions (atoms that have gained electrons) for each calcium. Calcium lactate is made for commercial use by mixing lactic acid with calcium carbonate or calcium hydroxide. In a commercial sense, calcium lactate is used as a thickener, firming agent, and flavor enhancer. And you can also find it in some of your favorite aged cheeses!

Calcium lactate supplements offer a very small amount of elemental calcium. So like we saw with calcium citrate malate, you’d have to consume a lot of capsules each day to reap any benefit.

Calcium ascorbate is the combination of calcium and ascorbic acid (that’s the fancy name for vitamin C). While it’s convenient to get both calcium and vitamin C from one type of calcium, calcium ascorbate supplements provide far more vitamin C than calcium. So from a bone health perspective, you’re better off getting your calcium elsewhere.

Calcium gluconate is the calcium salt of gluconic acid. The most common use of calcium gluconate is in a supersaturated injection, which is used to treat low blood calcium, high blood potassium, and magnesium toxicity.

Fun fact: Calcium gluconate was a conventional treatment for black widow spider bites! Calcium was thought to stabilize nerve membrane permeability, resulting in decreased neurotransmitter release. (However, studies have cast doubt over the effectiveness of calcium gluconate treatment for black widow bites, and it’s since fallen out of favor.)

As a supplement, calcium gluconate has the lowest level of elemental calcium on this list. That means you’d have to take a lot of capsules each day to reach the recommended daily intake of calcium.

The calcium in dolomite (a rock-forming mineral), oyster shell, and bone meal isn’t a unique chemical type of calcium. It’s actually mainly calcium carbonate. But calcium from dolomite, oyster shell, and bone meal warrants a separate mention on this list as it carries health implications you should be aware of…

Advocates of dolomite, oyster shell, and bone meal calcium will point to the fact they’re natural sources (although something being naturally occuring and natural to consume are two very different matters). Besides, these types of calcium are not advised for consumption because studies show they may contain dangerous levels of lead. Consuming toxic levels of lead can cause abdominal pain, vomiting, muscle weakness, and even seizures.

Choosing the right calcium supplement can be overwhelming. But when you have a guide like this, you’ll hopefully feel that the decision isn’t so difficult anymore.

After all, many of the calcium types on the list sport longer lists of cons than pros. And the most glaring weakness for all but one is the inability to stop bone loss.