Calcium Supplement Side Effects, Drug Interactions, and Safety Precautions

Calcium is vital for healthy bones. In fact, up to 99% of your body’s calcium is stored in your bones and teeth!

Yet, in recent years, calcium has been at the center of some controversy. A few poorly designed studies questioned the safety and efficacy of calcium supplements. Of course, this inspired a media frenzy to the effect that calcium supplementation is harmful and has no benefits…

But this is simply not true.

The research that caused such a stir was flawed at a basic level. Not only was it based on questionable data, but it failed to take into consideration the other essential ingredients your body needs to be able to use calcium properly.

The key here is that calcium is just one of the ingredients you need to build strong bones.

Keep reading to find out why the “calcium paradox” is a hoax, what side effects actually exist when it comes to calcium supplements, the ideal dose for healthy bones, and more!

Calcium Supplement Side Effect Myths

Do Calcium Supplements Increase Heart Attack Risk?

HeartThe term “calcium paradox” has been used to refer to a few different phenomena over the years.

The most well-known use of the term relates to the fact that in countries like Finland and Sweden where calcium intake is high, there’s also a high rate of osteoporosis. This applies to the United States and Canada too. But, as we’ll see in just a moment, there’s a simple explanation for this so-called paradox.

More recently, the calcium paradox was used to describe findings that suggested taking calcium actually increases the risk of heart attack and stroke.

As you can imagine, these findings caused quite a stir. You may recall seeing headlines warning that calcium supplements could increase your risk of heart attack. But this statement was taken out of context and based on flawed research.

Now, the study that showed these results was a meta-analysis of clinical trials published by Bolland et. al in 2010. It looked at 11 trials to investigate whether calcium supplements increased the risk of cardiovascular events. In these trials, researchers compared a calcium group with a control group.

But the original purpose of these clinical trials wasn’t to investigate heart attack risk. These studies may have been on calcium supplementation, but they were measuring outcomes like fracture risk and bone density.

So, cardiovascular risk factors weren’t taken into consideration when participants were divided into calcium and control groups. In other words, factors like whether a participant used to smoke or had a history of hypertension weren’t accounted for.

What this means is, it’s hard to say whether a cardiovascular event was caused by calcium supplementation, or some other factor when looking at these trials. Heaney et al. pointed this out when he refuted Bolland’s finding in 2012.

Heaney also explained that the reporting of “cardiovascular events” varied greatly from study to study. In fact, in seven of the clinical trials included, cardiovascular events were self-reported! And, of course, self-reported data may be less reliable.

Heaney cites a review by Lewis et al. to illustrate this point. Lewis investigated the seven clinical trials from Bolland’s study to see whether cardiovascular events were correctly self-reported. Now, 3.6% of participants in the calcium groups reported cardiovascular events. But after adjusting for false reports, the real rate of cardiovascular events was 2.4%.

So, the data Bolland based his conclusions on to begin with is questionable.

This point is further illustrated by the fact that– taken on their own– none of the clinical trials Bolland reviewed reported a significant effect of calcium on heart attack risk. It’s only after pooling the results of all 11 clinical trials that Bolland found a small increase in risk.

On top of all this, Bolland’s analysis had some huge blind spots. Most notably, he only looked at calcium. Yet, calcium is a team player. It cannot do its job without the help of two vitamins: vitamin D and vitamin K2.

As you may know, you need vitamin D to absorb calcium in the first place. Without it, you’d absorb less than 15% of the calcium you consume from food or supplements.

Incidentally, this explains the paradox we mentioned earlier where high calcium intake was associated with a high rate of osteoporosis. People in these countries are also largely deficient in vitamin D, so they have trouble absorbing calcium in the first place!

But vitamin D is just half the story. The other half is vitamin K— specifically vitamin K2. Vitamin K2 is responsible for directing the calcium you’ve absorbed. Think of it like a traffic conductor. Once calcium enters your bloodstream, vitamin K2 tells it where to go!

It does this by activating two proteins: osteocalcin and matrix-Gla protein. And these two proteins have very important jobs:

  • Osteocalcin directs calcium to where you need it most: your bones.
  • Matrix-Gla protein keeps calcium out of places you don’t want it like your arteries, heart, and soft tissue.

To sum up, you need both vitamins D and K2 to properly absorb and make use of calcium. If you take a supplement that contains calcium by itself, or even calcium and vitamin D, it may not help… unless you’re also getting plenty of vitamin K2 from your diet!

So, if calcium doesn’t make it to your bones without adequate vitamin K2, where does it go? Well, some of it may be deposited in your blood vessels instead, causing them to harden or calcify. And this can increase your risk for heart attack or stroke.

Yet Bolland’s conclusion that calcium supplements increase heart attack risk didn’t explain any of this. So you can see how, taken out of context by the media, his findings were highly misleading!

The truth is, as long as you’re getting the full complement of helper nutrients along with your calcium, you have nothing to worry about.

These major oversights led to a lot of criticism by medical experts. So, Bolland later tried to correct his mistake by examining calcium and vitamin D.

In 2012, he published a reanalysis of some of the data that was included in his earlier study. In this reanalysis, Bolland looked at whether taking calcium supplements with or without vitamin D affected risk of cardiovascular events.

Yet, as we’ve seen, vitamin D deals with absorption. It’s inadequate vitamin K2 paired with calcium that can impact cardiovascular risk. So, it’s no surprise that Bolland’s reanalysis came back with the same results as his original study. After all, it was subject to the same flaws!

But once again, Bolland’s claims got a lot of attention. This prompted the medical community to react. A group of academic and industry experts got together to take a closer look at the research on calcium supplementation and cardiovascular disease.

They reviewed 16 studies, involving over 358,000 individuals– the Bolland studies included– and they found, “No indication of a connection between calcium intake and atherosclerotic heart disease or stroke.”

But the damage was done. The media had their field day and headlines like, “Will Your Calcium Supplement Give You a Heart Attack?”, sold a lot more papers than, “Calcium Supplements Not Associated With Heart Attack”.

So, despite the fact that Bolland’s findings were quickly disproved, the idea that calcium increases the risk for heart attack and stroke persists to this day.

But this just isn’t true. This latest “calcium paradox” is a perfect example of the saying, “Don’t believe everything you read!”

Lara Pizzorno

Our Resident Bone Health Expert, Lara Pizzorno, recently shared a video over in the AlgaeCal Community where she discusses the weakness of Bolland’s studies in even more depth. If you’re an AlgaeCal customer, you can join the community to get free access to her video, and tons more exclusive bone health content.

Click here to watch Lara’s video!

Calcium’s actions aren’t paradoxical. Rather, they prove something that medical experts have known for years: the healthy use of calcium requires both vitamin D and vitamin K2.

That’s why AlgaeCal Plus contains calcium and vitamins D and K2 (as well as all 12 other bone-supporting minerals!). This multi-nutrient approach to bone health is the reason AlgaeCal Plus is the only calcium supplement clinically supported to increase bone density.

Do Calcium Supplements Decrease Fracture Risk?

Broken boneAs if the calcium and heart attack hoax wasn’t enough…

A few years later in 2015, Bolland et al. published another paper in the British Medical Journal called, “Calcium intake and risk of fracture: systematic review.

In this review, Bolland and his co-authors claimed that calcium, whether from food or supplements, and whether combined with vitamin D or not, has no effect on your risk of fracture.

Once again, this is absolutely not true. In fact, if you take a closer look at this review, you’ll see it actually proves the opposite!

Now, Bolland’s review looked at 26 randomized controlled trials. And every single one of these trials showed reduced fracture risk.

So, how can this study claim that calcium supplements have no effect on fracture risk? Well, first off, they considered a 5% lower risk of hip fracture and a 4% lower risk of forearm fracture “nonsignificant”.

The studies they reviewed also showed that calcium supplements reduced the risk of total fracture by 11% and vertebral fracture by 14%. But Bolland dismissed these studies by saying they were bias based on a “funnel plot inspection”.

In simple terms, a funnel plot inspection is a mathematical way of detecting bias in a group of studies. But this method is not without flaws! In fact, a review of funnel plots explains that,

“The use and appropriate interpretation of funnel plots and tests for funnel plot asymmetry have been controversial because of questions about statistical validity, disputes over appropriate interpretation (1, 2, 3), and low power of the tests.”

What’s more, only one of the studies Bolland and his co-authors chose to include in their review provided anything close to an adequate dose of vitamin D. (Remember, you need adequate vitamin D to absorb calcium effectively.)

The one study that came close to supplying adequate vitamin D provided 1,600 IU/day. That’s just within the range of the current Endocrine Society recommendations for healthy adults. The lowest dose recommended for healthy adults is 1,500 – 2,000 IU/day.

In all the other studies Bolland considered, dosages of vitamin D ranged from as low as 240 IU/day to 1,200 IU/day. That’s insufficient vitamin D for virtually everyone!

In fact, the latest clinical research shows that 1,200 – 2,000 IU/day isn’t enough to restore vitamin D if you’re deficient. And many of us are! The latest National Health and Nutrition Examination Survey (NHANES) tells us that 39.92% of people in the U.S. are vitamin D deficient.

So, the studies included in this review didn’t provide an adequate dose of vitamin D to restore deficiency. This means we can’t be sure whether participants were able to properly absorb the calcium provided. And if you can’t absorb the calcium you consume, how can it strengthen your bones and prevent fractures?

Not only that, Bolland failed to take into account vitamin K2… again. And as we’ve seen, vitamin K2 is essential for directing calcium to your bones.

Despite all this, calcium alone or with vitamin D reduced fracture risk in every single one of the studies included in Bolland’s review. So, if calcium all by itself could have even a small effect on fracture risk, imagine what it could do when supported by the proper nutrients?

From the AlgaeCal studies, we know that when calcium teams up with the proper nutrients, it can increase bone density. But to get this result, the calcium in AlgaeCal is supported by vitamins D, K2, C, and all 12 other essential minerals your bones craves.

The big takeaway here is that it’s a team effort when it comes to bone health.

And calcium is the quarterback on that team. But it can’t get to the endzone without the help of its teammates!

Yet Bolland neglected to explain any of this in his findings. And once again, the press picked up on these incomplete findings and published a flurry of misleading articles.

But really, the science (Bolland’s study included!) shows that our bones need calcium AND the full team of nutrients to remain strong, healthy, and fracture-free.

All this to say, be wary of bold claims made by the media— even if they’re seemingly backed by science. More often than not, there’s more to the story. And as we’ve seen, not all research is equally well-designed.

Common Calcium Supplement Side Effects

At this point, you’re probably wondering what calcium side effects do exist. Well, the answer to this question is two-fold.

If we’re talking about traditional rock-based calcium supplements, then yes, there are some side effects to list. But as we’ll see shortly, there’s also a calcium supplement with no adverse side effects.

Traditional calcium supplements though can cause some issues because of what they’re made of— and what they lack as a result!

Almost every calcium supplement on the market is made of marble or limestone. This form of calcium is called “calcium carbonate” or “calcium citrate”. So really, these terms refer to supplements made from ground up rock bound with some form of acid.

But, it’s not the form of calcium that’s at fault. It’s the fact that traditional supplements only provide calcium. And your body has a hard time tolerating calcium on its own! (We’ll explain the main reason for this in the next section.)

That’s why traditional supplements can cause side effects like gas, bloating, and constipation.

On top of these unpleasant side effects, traditional supplements lack the helper nutrients your body needs to properly use calcium. As we’ve seen, you need vitamins D and K2 to absorb and direct calcium to your bones.

Yet most calcium supplements provide just calcium or calcium and vitamin D. And that’s far from all your body needs!

In addition to vitamins D and K2, there are 13 essential minerals (calcium included!) that you need to support healthy bone. And when all these nutrients come together— the way nature intended— you won’t suffer any of the adverse side effects listed above.

That’s why AlgaeCal’s plant-based, multi-nutrient calcium supplements have no adverse side effects. We’ll go over this in more depth a little further down the page!

Can Too Much Calcium Cause Constipation?

DigestionConstipation is a common side effect of traditional calcium supplements.

And it’s the perfect example of why the multi-nutrient approach is so important!

Calcium only causes these issues when taken in excessive amounts and not properly balanced with its key partner nutrients. In fact, it’s well known that taking traditional rock-based calcium supplements— that provide too large a calcium dose— can cause constipation and an upset stomach.

But why might this be?

Well, a common reason for these digestive issues is inadequate magnesium intake. Calcium and magnesium work together to support many of the body’s functions. And one of these functions is digestion.

In fact, it’s impossible to digest food without magnesium! Your body needs magnesium to perform every single phase of digestion. It makes sense then that constipation would be a common side effect of magnesium deficiency.

You also need magnesium to properly use calcium. So, maintaining a proper balance of calcium and magnesium is crucial if you want to strengthen your bones without suffering unpleasant side effects like constipation!

The important takeaway here is: don’t give up your calcium supplement— you absolutely need it for healthy bones. Just make sure you choose a supplement that contains a balance of calcium and magnesium. Studies show that the optimal ratio of calcium to magnesium is 2:1.

You’ll also want to make sure your calcium supplement contains the other essential nutrients you need for strong bones like vitamins D and K2! When all these nutrients come together in their proper proportions, like in AlgaeCal Plus, you’ll give your body its best chance to build new bone.

Calcium Supplement Interactions

When it comes to calcium supplements, there are a few safety concerns and potential interactions to be aware of.

In terms of interactions, there are certain medications that could cause issues if taken alongside calcium supplements. In some cases, you can work around this by taking your calcium supplements and your medication at different times of day.

As always, it’s a good idea to consult with your healthcare professional before starting a new supplement regimen— especially if you’re on any prescription medication.

Another issue to be aware of is that certain health conditions can interfere with calcium supplementation. As an example, hypercalcemia is a condition where you have too much calcium in your bloodstream. If you have hypercalcemia, taking additional calcium could cause more harm than good!

So again, if you have any existing health conditions, it’s best to check with your healthcare professional before taking a new calcium supplement.

A Plant-Based Calcium Supplement with NO Adverse Side Effects

As you now know, the main reason your average supplements have side-effects is because they lack calcium’s key partner nutrients.

The reality is your bones need more than just calcium to stay dense. They need calcium and 12 essential minerals from natural sources (plus vitamins like C, D3, and K2). Yes, natural sources… because nowhere in nature do you find a food that contains just one or two nutrients!

To put it simply, nature knows which vitamins support which minerals, in the combinations and dosages that are ideal for your body.

That’s what makes AlgaeCal’s plant calcium so special.

AlgaeCal calcium comes from a unique strain of ocean algae off the coast of South America. This algae absorbs all the trace minerals from the ocean– and since it’s a living thing– “pre-digests” all the nutrients for you. That’s why you won’t experience gas, constipation, or an upset stomach when you take AlgaeCal Plus.

Calcium and Blood Pressure

The “Plus” in AlgaeCal Plus stands for the vitamins and minerals added to the already nutrient-dense algae! We add vitamins C, D3, and K2, plus magnesium and boron to round out all the nutrients your bones need. Better still, these nutrients are combined in the ideal amounts for your body. Just the way nature intended.

So when you take AlgaeCal Plus, two things are sure to happen. Not only will you avoid the common side-effects of your typical store-bought calcium, but you’ll actually nourish your bones with the precise nutrients they require. (In fact, you’ll actually build new bone, no matter your age— see here for more details.)

But you don’t need to trust nature to believe there aren’t any side-effects from AlgaeCal Plus! Human clinical studies back this up.

In one study published in the Nutrition Journal, 216 women and men followed an AlgaeCal Plus regimen for six months. At the end of the six months, not a single person showed any side-effects– as confirmed by a rigorous 43 blood test panel– or reported a drop in their quality of life.

What about long-term use of AlgaeCal Plus? Well, 172 postmenopausal women in their mid-60s put it to the test. Researchers published their findings in the Journal of the American College of Nutrition after seven years of tracking the women!

They found none of the women experienced adverse effects or safety concerns. And again, these results were confirmed through a panel of 45 different blood chemistries to measure changes while on AlgaeCal Plus.

All this to say, if you want to avoid adverse side effects from calcium supplementation, look to natural, plant-based calcium! Your bones (and your entire body) will thank you.