Just drink milk for strong bones, right? Sometimes it's not quite that simple.
Calcium is one of the most important minerals in your diet. If you want a better shot at strong bones, check out the following calcium supplement rankings.
This guide comes in two parts, a top-10 review and a guide to using calcium supplements.
1. Citracal Calcium +D3 Slow Release
Citracal is a rare bird among supplements: it's cost-effective, lab-verified, and simple.
Citracal's slow release formula means you take the dosage once per day. Other calcium supplements need to be divided up into smaller doses throughout the day; otherwise, the calcium passes through your body too quickly and not all of it is absorbed.
The slow release formulation obviates this problem.
The supplement uses a binder called hydroxypropyl methyl cellulose to achieve this slow release effect. Though it's a long and technical chemical name, it's a nontoxic plant-derived compound that forms a gel when it comes into contact with water.
This slows the rate at which calcium is released from the tablet into your digestive tract.
Citracal uses a blend of calcium carbonate and calcium citrate to provide the mineral source of calcium, and also provides 1000 IU of vitamin D per capsule alongside 80 mg of magnesium, which makes up 20% of your recommended daily intake.
Laboratory testing reveals that the supplement actually contains 1350 mg of calcium per tablet (the label reports 1200 mg) and almost exactly 1000 IU of vitamin D. It also contains no heavy metals or toxic contaminants, and the lack of “extra” ingredients is a boon for anyone looking for a straightforward, no-nonsense calcium supplement to take daily.
2. Bluebonnet Calcium Citrate and Vitamin D3
The calcium supplement formulation from Bluebonnet is perfect for the minimalist: it contains very few extraneous ingredients.
In fact, aside from its stated vitamin and mineral content (250 mg of calcium, 200 IU of vitamin D, and 100 mg of magnesium), Bluebonnet Calcium Citrate contains only five other ingredients, and all of them are binders or stabilizers to keep the tablets intact.
Its laboratory purity ratings are excellent. Independent testing has verified that it contains within 2.5% of its label-claimed calcium and vitamin D content, so you know you're getting exactly what's been promised on the bottle.
Because of the simplicity of the tablet design, you should take Bluebonnet Calcium Citrate in smaller, separate doses to get optimal results.
If your goal was to supplement your diet with 1000 mg of calcium (100% of your recommended daily intake), you would need to take four tablets of Bluebonnet Calcium Citrate per day.
Taking these at different times throughout the day, as opposed to all at once, is a more effective way to deliver your body the calcium it needs (1).
3. Kirkland Signature Calcium Citrate Magnesium and Zinc
Kirkland's calcium offering might be the most cost-effective calcium supplement on the market. Its formulation employs calcium citrate to deliver the promised calcium, as well as magnesium oxide and zinc oxide for the other three minerals included in the tablets.
Each tablet provides 250 mg of calcium, 40 mg of magnesium, and 5 mg of zinc.
While you'd have to take four tablets to get your recommended 1000 mg of calcium (disregarding the rest of your diet, of course), this is no problem when each bottle comes with 500 tablets!
In terms of raw cost per unit of calcium, Kirkland is impossible to beat.
Not only that, it can hold its own in the analytical lab, too. The analytically determined calcium content is exactly 250 mg per tablet, though its vitamin D content is actually about 30% higher than the claimed value. This is not a concern, as vitamin D can be taken in much higher doses without any ill effects.
As for why Kirkland and other formulations contain magnesium and zinc, scientific investigations have found that these nutrients are critical for bone health as well.
Magnesium intake is positively associated with bone density, and low levels of zinc have been associated with osteoporosis in at least two studies (2). Since both zinc and magnesium are included in Kirkland Signature Calcium, you don't have to worry about this.
4. GNC Calcium Plus 1000
This is one of the brands you're likely to be able to find in-person at a brick and mortar store. GNC's calcium supplement is straightforward and no-nonsense: each caplet contains 333 mg of calcium, 266 IU of vitamin D, and 166 mg of magnesium.
The only other ingredients are a binder, a coloring agent, and a vegetable-based stabilizer.
Like a few other supplements, GNC Calcium Plus exceeds its stated mineral contents by a good margin. According to independent lab testing, each tablet contains a 28% excess of calcium and an 11% excess of vitamin D.
This is better than the converse situation—a deficit of the claimed ingredients—but is still less desirable than being spot-on with each tablet's dosage.
GNC Calcium Plus is a good choice if you're primarily looking for a solid dosage of calcium and vitamin D at a low cost per-dose, without any extra frills like plant-derived calcium, a slow-release formula, or other minerals like zinc.
5. New Chapter Bone Strength Calcium
This supplement is the #1 seller across all categories of calcium supplements on Amazon.com. How does it stack up? It comes in tablets that provide 257 mg of calcium each.
The calcium in New Chapter Bone Strength is derived from algae—most supplements use a mineral source, either calcium citrate or calcium carbonate.
Though this is different, there isn't any evidence multiple sources are better. Like almost all calcium supplements, New Chapter comes with vitamin D as well (333 IU per tablet), which has been demonstrated to boost calcium absorption in scientific studies (3).
Unlike other products, this supplement also provides a small amount of vitamin K, which may potentially play a role in preventing osteoporosis and improving bone density, according to a scientific report by N.C. Binkley and J.W. Suttie at the University of Wisconsin-Madison (4).
Since each tablet only contains 257 mg of calcium—about 25% of your recommended daily intake—you'll find yourself going through the bottle fairly quickly, especially if you don't get much calcium elsewhere in your diet.
Over time, this could get expensive. New Chapter Bone Strength is a good choice if you find that citrate and carbonate-based calcium upsets your stomach, but it isn't the best value, and its quality has not been independently lab-verified.
6. Nature Made Calcium with Vitamin D
This brand is often available at your local drug store, and offers a fairly cheap and simple form of calcium and vitamin D. Each tablet contains 600 mg of calcium and 400 IU of vitamin D, along with several binders and stabilizers.
Notably, this supplement also includes some of the same binders used in Citracal's extended release formulation—it's likely that this product also has a slow-release effect, which is what allows it to have more calcium per tablet than other supplements.
Recall that if a single dose of calcium is too high, some of it will pass through the body and fail to be absorbed.
Lab testing reveals that Nature Made Calcium with Vitamin D is fairly well-controlled in its manufacturing. The capsules contain exactly the claimed amount of calcium, and an 18% excess of vitamin D.
The only other notable ingredient is gelatin—unlike other supplements, Nature Made Calcium is in capsule form, not a tablet, and thus contains gelatin, which is made from animal products. If you are a vegetarian or a vegan, look elsewhere to fill your calcium needs.
7. Swanson Calcium Citrate and Vitamin D
The calcium and vitamin D offering from Swanson Health Products is another one for the simplistic camp. Each tablet contains 310 mg of calcium and 200 IU of vitamin D. The only other ingredients are vegetable-based binders and stabilizers.
If you are looking for zinc or magnesium alongside your calcium and vitamin D, you're out of luck, but the good news is that Swanson's calcium supplement sources all of its calcium from calcium citrate, which is a more readily-absorbed form of calcium than calcium carbonate, which is used in some other supplements.
It scores well on purity, too: lab testing found that the actual calcium content was only 13% higher than stated on the label, and the vitamin D content was 7.5% lower.
The relatively low vitamin D content might be a problem if you don't take a vitamin D supplement and you live in a region which does not get much sunlight during the winter months—most people who live in such regions should consider a vitamin D supplement, but that's a topic for another day.
8. Solgar Calcium Magnesium with Vitamin D3
The calcium/magnesium supplement by Solgar is a minimalist-style supplement, even down to the packaging.
A simple amber bottle and brown label identifies the product, which consists of small tablets offering 200 mg of calcium each, alongside 100 mg of magnesium and 80 mg of vitamin D.
You'd need to take five tablets per day to reach 1000 mg of calcium—the Food and Drug Administration's recommended daily intake.
In terms of its reported versus actual content, Solgar has some discrepancies. Analytical testing found that the actual calcium content is 25% higher than reported, and its vitamin D content is 20% higher.
This is not a strictly bad thing, since you are getting more value in terms of milligrams of the vitamin per dollar spent, but it may indicate there are some quality control issues in Solgar's manufacturing process.
Additionally, the vitamin D content leaves something to be desired. Other supplements contain substantially more vitamin D and do so at a lower cost, making it hard to rank Solgar Calcium much higher.
9. Rainbow Light Calcium Citrate Mini-tablets
This calcium supplement is intended to be used in the original sense of the word—as a supplementation to your usual dietary calcium intake. As the name suggests, the tablets are smaller in size and have somewhat less calcium per tablet than a typical supplement.
Each tablet provides 200 mg of calcium and 200 mg of vitamin D.
It's also designed to be magnesium free, which is nice if you already know you get an excess of magnesium in your diet (either from food or from another supplement).
The supplement also includes boron, spirulina, and horsetail extract, which are supposed to enhance calcium absorption and provide “natural energy,” though these claims are not substantiated by solid research (5).
Despite this it scores well on laboratory testing, with the supplement providing 13% more calcium and 26% more vitamin D than its stated amounts on the label. The quantity of boron and herbal extracts actually present was not tested.
If you already know you're interested in a spirulina or horsetail extract, Rainbow Light Calcium might be a good choice, but if not, these ingredients increase the cost and likelihood of an adverse experience without a clear benefit.
10. Solaray Calcium Magnesium Zinc
You might term Solaray's approach to calcium supplementation as the “maximalist” strategy. Each capsule provides a pretty-standard 250 mg of calcium, 125 mg of magnesium, and 6 mg of zinc.
However, the way in which those minerals are provided is unlike other supplements: the calcium comes from four different sources, calcium carbonate, calcium hydroxide, calcium citrate, and calcium amino acid chelate.
The magnesium is likewise sourced from a variety of ingredients; magnesium oxide, magnesium citrate, and magnesium amino acid chelate round out the magnesium sources. The zinc is only from one source, an amino acid chelate.
The stated reasoning for the broader range of sources for these vitamins and minerals is to boost absorption. A 1985 study did find that calcium citrate is more readily absorbed by the body than calcium carbonate (6), but if this was the main reason for using calcium citrate, it's unclear why calcium carbonate remains in the formulation.
Amino acid chelates are thought to be more absorbable than inorganic versions of the same mineral, but there is a lack of comparative studies on amino acid chelates versus mineral salts.
Regardless, it is still clear from scientific research that inorganic salts like calcium carbonate or citrate are readily absorbed.
Solaray's formulation also includes some herbal supplements—whole rice concentrate, alfalfa leaf, watercress leaf, dandelion root, and parsley leaf—but it does not specify the purpose or role of these amino acid concentrates.
Despite its popularity, it's hard to rank Solaray Calcium Magnesium Zinc highly without more information and more research on the reasoning behind the various sources of minerals were chosen, plus the role of the herbal supplements in the tablets.
Part 2: What does calcium do and who should take a supplement?
Calcium supplements are a good way to ensure your bones are as strong as possible when you get older. Calcium salts are one of the primary constituents of skeletal bones, and without sufficient calcium intake, you risk having low bone density and osteoporosis.
This is not just a concern for older people; much of your ultimate lifetime bone density is determined in adolescence, and insufficient calcium intake in middle age can cause bone density loss to accelerate sooner and more rapidly (7).
Benefits of calcium supplementation
Osteoporosis is a major public health concern. According to a 2014 study by Nicole C. Wright and other researchers at the University of Alabama Birmingham, 10.3% of all adults age 50 or older in the United States have osteoporosis. Osteoporosis is often seen as a women's health issue, and indeed, about 80% of these cases are in women (representing almost 16% of all women over age 50).
However, there were still over two million men over 50 in the United States who have osteoporosis (8). On top of this, an even larger fraction (some 44% of all adults over 50) of the population has low bone density—these people are at risk for developing osteoporosis in the future.
The good news is that there are some well-known ways to help prevent osteoporosis, and calcium supplementation is one of them. Calcium supplementation seems particularly effective when combined with vitamin D, which boosts calcium absorption (9), and exercise plays an important role in preventing bone loss.
In fact, one 1991 study found that calcium supplementation alone was significantly less effective at preventing bone loss than calcium supplementation combined with exercise (10).
When it comes to what kind of calcium supplement to take and what dosage you should aim for, there are some pretty solid guidelines that can be found in the scientific research.
A 2007 scientific article in the medical journal The Lancet pooled 29 randomized clinical trials of calcium supplementation for reducing loss of bone density and conducted a meta-analysis on the results (11).
Drawing from a population of over 63,000 study participants, the researchers found that calcium supplementation results in a substantial and statistically significant reduction in the risk of bone fracture and in the rate of bone density loss.
Note that supplementation does not increase bone mass—that's very difficult to do once you're into your thirties, forties, or fifties.
Pooling massive sets of data like this allows you to find some pretty cool trends. For example, the researchers found that the compliance rate of any given subject—i.e. how often they took the supplement—was associated with a 24% lower risk of fracture, meaning that sticking to your supplementation schedule pays big dividends.
On top of that, there's clear evidence for optimal dosing. Clinical trials that used dosages of more than 1200 mg of calcium and more than 800 IU of vitamin D per day were more successful than those that used less.
The recommended daily intake for calcium is only 1000 mg and the recommended daily intake for vitamin D is only 400 mg—the evidence from the research indicates that these values might need to be revised upwards, at least for adults over age 50.
As for the constituents of the supplement itself, there are a number of studies that suggest that, all else equal, a calcium supplement that contains calcium citrate is superior to one that contains calcium carbonate.
The citrate form of calcium appears to be absorbed more effectively, as demonstrated by a 1988 study by Jean A. Harvey, Margaret M. Zobitz, and Charles Y.C. Pak (12).
Side effects of calcium
While conventional wisdom holds that an excess of calcium in your diet, either through supplementation or normal dietary intake, puts you at risk for kidney stones, scientific research shows that the opposite is true—if anything, a high calcium intake reduces your risk of kidney stones.
This was the finding in a 1993 study published by Gary C. Curhan and other doctors at Harvard School of Public Health; a prospective study of 45,000 men aged 40 to 75 found that calcium intake was inversely related with the risk of kidney stones, i.e. more calcium equals fewer kidney stones (13).
There is some conflicting evidence on whether high levels of calcium supplementation may be associated with an increased risk of heart disease.
On one hand, a 2007 study conducted in New Zealand found that calcium supplementation increased risk of heart disease and stroke among postmenopausal women (14). On the other, a 1998 study by researchers in South Carolina, Minnesota, and Pennsylvania found that high levels of calcium intake reduced the rate of heart disease in postmenopausal women (15).
The jury is still out on this, so you should talk to your doctor if you're concerned about the effects of supplementation on your dietary risk. There's no one answer for everyone; whether supplementation makes sense for you depends on your diet, your overall health status, and your risk for heart disease, osteoporosis, or both.
In sum, there is strong evidence that taking a calcium and vitamin D supplement can help keep your bones strong and reduce your risk of osteoporosis and bone fractures as you get older. This is important as you approach your fifties, whether you are a man or a woman.
Look for a high-quality calcium supplement, ideally that uses calcium citrate as its mineral source, and definitely check to make sure your supplement includes a substantial amount of vitamin D as well.
If your goal is to prevent bone loss, you'll get the best results with doses of at least 1200 mg of calcium and at least 800 IU of vitamin D per day.
To ensure you're keeping your bones as strong as possible, add weight-bearing exercise like walking, jogging, or weight lifting to your daily routine, as calcium supplementation is most effective when combined with an exercise regimen.