Can Calcium Supplements Cause Constipation?

Can Calcium Supplements Cause Constipation?

Posted by AlgaeCal on 2024 Apr 15th

Unfortunately, most calcium supplements cause constipation and other gastrointestinal issues like bloating, gas, and cramps. This is problematic — especially when you consider that 43% of the American population uses calcium supplements.1

Beyond the discomfort, these gastrointestinal issues are a big problem because they can keep your patients from taking their recommended dosage of calcium every day.

So we gathered the latest research to shed light on why calcium supplements cause constipation. Plus, we provide a downloadable education tool, 8 Common Causes of Constipation and What to Do About It.

It’s ready for you to share with your patients so they won’t have to worry about missing a single dosing schedule. Now they’ll be able to focus on building bone strength without missing a beat.

Why Calcium Supplements Cause Constipation

Most calcium supplements cause constipation because they supply only calcium or just calcium and vitamin D.

It takes a variety of nutrients for proper absorption of calcium, especially magnesium. Magnesium is a natural laxative and thus counterbalances the constipating effects of calcium.

If your patients’ calcium supplement and/or their diet lacks magnesium then constipation can occur. But with enough magnesium, their colon walls will relax helping them pass stool along.

Additionally, magnesium attracts water, meaning more water gets to the colon and softens the stool. As you likely know, calcium contracts muscles.

So getting too much calcium makes the muscle walls of the colon contract, making it harder to pass stool. The longer stool sits in the colon, the more water is pulled out of it. This makes the stool dense and hard, making it significantly harder to pass and likely painful.

Magnesium reduces tension on the walls of the colon which allows for a normal peristaltic action.

Peristaltic action, also known as peristalsis, means “a radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube”. This means the rhythmic movement of the intestinal tract that moves food from one end to the other.

Regularly including magnesium-rich foods in the diet is great for overall health, plus it will keep the body regular.

With that being said, there are additional reasons why a calcium supplement might cause constipation.

Patient Tool: 8 Common Causes of Constipation and What to Do About It

Too Much Supplemental Rock Calcium

It is well known in research circles that taking a calcium supplement that provides too large a dose of elemental calcium causes upset stomach and constipation.

The most common type of calcium and the one that causes the most gastrointestinal discomfort is from rock. It’s described on the label as ‘calcium from calcium carbonate or calcium citrate.

According to a 5-year, double-blind, placebo-controlled study,2 the occurrence of constipation was increased with the use of calcium carbonate (among 1,460 participants, 13.4% of the calcium group experienced constipation; 9.1% of the placebo group experienced constipation).

So why do we eat rock calcium? Because rocks are cheap, rich in calcium (40%)3 and capable of slowing bone loss. As you likely know, we naturally lose about 1% of bone per year after age 35. For decades, rocky calcium carbonate has cut that bone loss down by a little bit.

But that wasn’t without its drawbacks. For instance, in several random control trials4 participants receiving calcium reported higher rates of gastrointestinal issues (GI). These problems were described as:

  • constipation
  • excessive abdominal cramping
  • bloating
  • upper GI events
  • GI disease
  • GI symptoms
  • severe diarrhea or abdominal pain

These gastrointestinal issues happen because the alkaline calcium carbonate neutralizes stomach acids. If stomach acids aren’t there to digest food and improve mineral absorption, then it makes sense that constipation, bloating, gas, and cramps will result.

Then there’s the fact that some people are getting more than their recommended dietary allowance for calcium5 because they aren’t compensating for the calcium they get in their food each day. This can also lead to gastrointestinal issues.

Fortunately, research confirms it isn’t necessary to reach for the highest dosage of calcium available.

Consider that a recent meta-study has shown that lower dose calcium supplementation, combined with vitamin D, was most effective at preventing osteoporosis-related fractures, whereas high dose (1,000 mg) calcium supplementation was not. 6,7,8

In one human study,9 three groups of post-menopausal women each took different AlgaeCal formulations (not exceeding 750 mg of calcium) with all groups increasing bone density at one year.

The smallest average increase among the 3 groups was 1.3% — an extraordinary result. Plus, no negative gastrointestinal effects were observed.

Unlike traditional calcium supplements made from rock, AlgaeCal is a natural plant-sourced calcium. So it’s easier for the body to absorb since it’s similar to the calcium you get from eating vegetables such as broccoli, kale, and peas.

Too Much Supplemental Iron

Iron supplements10 are notorious for causing constipation. And that’s why many people don’t follow through with their supplementation. While there are some forms of iron that are easier to absorb, they tend to come at a higher cost.

Too Much Sugar and Unhealthy Fats

Sugar and fats can displace high fiber foods, leading to constipation. They can also have a negative impact on gut health.

As you may know, the gut microbiome is a collection of trillions of bacteria and 80-90% of the immune system depends on a healthy gut. There are more gut bacteria than there are cells in the body.11

Unfortunately, consuming too much sugar and/or unhealthy fats feeds unhealthy bacteria in the gut and causes inflammation. And when the intestinal tract swells with inflammation, it’s difficult for food to move through it.

Lack of Physical Activity

Walking helps move and massage the food in the digestive tract, using gravity to help move it along. Yoga, jogging, Pilates, and the like will all have the same benefits.

They also help strengthen muscles, including the intestinal tract, making it much easier to move things both inside and outside the body.

Imbalanced Gut Bacteria

We all get by with a little help from our friends, including the healthy bacteria that make digestion and proper nutrition possible. Healthy bacteria help break down food to extract maximum nutrition and keep it moving along.

Certain Medications

A common side effect of several medications is constipation. The list of medications that can cause constipation12 is lengthy. But some of the top offenders are opioids, NSAIDs, antihistamines, antacids, blood pressure medications and diuretics.

Lack of Water

Water is vital for healthy digestion. Dehydration wreaks havoc on the human body, including the digestive tract.

When dehydrated, the body will conserve as much water as possible for cerebral fluid, blood volume, and respiration.

Lack of Magnesium

Magnesium is needed to relax muscles, including those of the gastrointestinal tract. Magnesium is also an electrolyte that affects water balance.

Plus, it also has bone-building properties. Moreover, magnesium helps the body properly absorb and utilize calcium and vitamin D.

As you know, calcium and magnesium work together. Calcium in general, constricts tissues like our blood vessels and intestines while magnesium relaxes them.

For this reason, insufficient magnesium — in relation to calcium — can promote constipation.

Additionally, low magnesium intake13 causes a host of other health problems, including irritability, tense muscles, and sensitivity to noise. About half of the American public is magnesium deficient.

Natural Remedies for Constipation

To keep constipation at bay, it’s important to get 25-30 grams of fiber a day by eating fiber-rich foods such as fruits, vegetables, legumes, nuts and whole grains.

Another way to maintain a happy gut is to introduce healthy bacteria into the diet. An excellent way to do that is to consume probiotic foods such as kefir, yogurt, kimchi, sauerkraut, kombucha and homemade shrubs.

It’s also a good idea to eat a variety of magnesium-rich foods throughout the day, every day. This includes dark-green vegetables, whole grains, beans, nuts and seeds.

Not to be overlooked is the nutrient-packed kiwi. It exceeds most other fruits in its content of key micronutrients including potassium, magnesium, and calcium.

Recent research14 in cells, animals, and humans has demonstrated that kiwifruit, particularly the gold variety, can increase the uptake and retention of the essential dietary minerals iron, calcium, phosphorus, and magnesium.10

Moreover, It’s been reported that kiwi eases constipation15 as well as prunes and psyllium powder. Plus, it’s better tolerated.

Of course, it’s not enough to simply eat healthy foods — it’s important to avoid eating unhealthy ones too. So that means reducing or cutting fried foods along with foods that have added sugar and refined carbohydrates.

The same goes for unhealthy fats. They should be swapped out for naturally-occurring healthy fats that have a soothing, inflammation-reducing effect. These can be found in plant-based oils, seeds, nuts and fatty fish.

Also, caffeine consumption should be limited to 2 to 3 cups of caffeinated beverages a day. Avoiding sugary drinks and/or those with toxic food additives is important too. It’s far better to drink 8 to 10 glasses of water every day — especially since it’s vital for healthy digestion.


Constipation is an unwelcome side-effect. But that doesn’t mean your patients should give up on taking their calcium supplements. After all, their bone health is at stake.

Instead, your patients should try a natural, plant-based calcium supplement.

It will be much easier on their stomachs because the minerals are chelated by the plant making them more body-friendly!

And, unlike traditional rock-based calcium supplements, plant-based calcium can make their bones stronger because it contains all the nutrients their bones need.

After all, bone loss isn’t a loss of calcium. It’s a loss of all the minerals in the bones. So if your patients’ rock-based calcium supplement contains only calcium, that’s bad news. They’re missing 12 vital bone-supporting minerals.

The best calcium supplement will provide your patients with all the nutrients their bones need — minus the unwanted side-effects like constipation, gas or bloating!

When looking at calcium supplements, consider these factors:

True Cost: If your patients’ calcium supplement is just calcium alone or calcium and vitamin D it is not enough. Your bones are made up of much more than that! They need magnesium, vitamin K2, D3, C, boron, and trace minerals.

Although vitamin D is known for helping the body absorb calcium in the intestines, by itself it can’t do anything useful until it is converted to an active form within the body called vitamin D3. It is well established that vitamin D3 is the best-absorbed form and the one used in bone and cancer research. Vitamin D3 enables calcium and the mineral phosphate to be absorbed to mineralize bones.

Another vitamin that plays a key role in bones’ ability to fully absorb calcium is vitamin K2 in the form of MK-7. When calcium is deposited in the body, vitamin K2 (MK-7) comes along and transports it in proper amounts, to the proper areas. For instance, vitamin K2 (MK-7) directs calcium into the bones where it’s needed, and away from soft tissues it’s prone to collect, like your arteries and kidneys.

Moreover, vitamin C helps increase intestinal calcium absorption. After you take a calcium supplement your body works to dissolve it in the stomach and vitamin C helps this process. Once the calcium supplement is dissolved, it’s available to be absorbed through the intestinal wall and enter the bloodstream, on its journey to the bones.

Of course, bones also benefit from trace minerals such as boron which helps bones retain healthy calcium and magnesium by reducing the amount of each that’s lost through urine. And boron lengthens the amount of time that vitamin D remains available in the body, allowing it to absorb more calcium. Also, boron strengthens osteoblast (bone-building) activity and the mineralization of bone cells — two bone-healthy benefits everyone can benefit from.

Buying all of those separately is expensive and a hassle. Instead, your patients could get an all-in-one bone formula.

Amount of Calcium: Remember that the body can only absorb 500 mg of calcium at a time. Anything beyond that makes you feel sick to your stomach and leads to constipation. In addition to constipation, too much calcium at once or over time has potential health risks like calcium depositing into soft tissues and kidney stones.

Confidently help your patients take charge of their bone density today by scheduling a consultation.

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  2. Kelvin Li, Xia-Fang Wang, Ding-You Li, Yuan-Cheng Chen, Lan-Juan Zhao, Xiao-Gang Liu, Yan-Fang Guo, Jie Shen, Xu Lin, Jeffrey Deng, Rou Zhou, and Hong-Wen Deng. "The good, the bad, and the ugly of calcium supplementation: a review of calcium intake on human health." Clinical Interventions in Aging. (2018). doi: 10.2147/CIA.S157523
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