Exploring Calcium Supplements: Types and Absorption Tips

Types of Calcium Supplements and How to Optimize Absorption

Has your doctor ever recommended that you start a calcium supplement, and then you get to the store to buy said calcium only to realize there are several calcium options, and you have no clue what to get? 

A common question I get asked by patients is regarding types of calcium, so I thought, let’s break it down and briefly summarize it all in one place.

Also, if you are someone living with acid reflux, gastroesophageal reflux disease (GERD), irritable bowel syndrome (IBS), or inflammatory bowel disease (IBD), check out this article on meeting your calcium needs with GI disorders first, as it can be a beneficial overview of calcium about GI conditions.

So, let’s take a brief moment to discuss calcium.

Calcium is a mineral that your body needs to build and maintain strong bones and is the most abundant mineral. Almost all calcium in the body is stored in your bones and teeth (hello structure and hardness). Your body needs calcium for muscles and nerves to carry messages between your brain and all body parts. 

After about age 30, bones slowly lose calcium. This shows that getting enough calcium from our food is very important, especially as we age. If we do not get enough calcium in our diet, it will be removed from where it is stored in our bones. Over time, this will cause weak bones and, eventually, what is called osteoporosis. 

So, now that we have a background of calcium- let’s go over some common forms of calcium supplements. 

• Calcium carbonate - provides 40% of elemental calcium, meaning it is better absorbed by the body. It does need stomach acid for absorption; therefore, it should be taken with meals.
• Calcium citrate - provides 21% of elemental calcium. It does not rely as much on stomach acid for absorption and can be taken without food.

Other forms of calcium that you may see are calcium gluconate, calcium sulfate, calcium ascorbate, calcium microcrystalline hydroxyapatite, calcium lactate, and calcium phosphate. 

A key tip to remember: 

Calcium is best absorbed when you take 500 mg of calcium or less at a time. Some doctors may recommend more than that, but if that’s the case, it may be better to break up the dose and take it more frequently throughout the day. For example, if your doctor recommends 1,000 mg per day of calcium, you may want to take 500 mg in the morning and 500 mg in the afternoon. 

Are there any reported side effects when taking calcium? 

Some uncomfortable side effects that may arise when taking a calcium supplement include gas, bloating, and constipation. If you experience any of these issues, try taking your calcium with a meal or maybe even switching the form of calcium you take to see if it would be better tolerated.

Are there any calcium-drug interactions? 

There can be calcium-drug interactions, and here are a few examples. For people taking proton pump inhibitors, please know that this medication may decrease your calcium absorption. Also, calcium can compete or interfere with iron, zinc, and magnesium absorption. Also, calcium carbonate may interfere with Levothyroxine (a common medication used to treat thyroid issues). Taking calcium within 4 hours of taking Levothyroxine may decrease your absorption.  

As a reminder, it is always best to speak with your physician or registered dietitian before starting any supplements to ensure they are appropriate for you. 

1. _{U.S. Department of Health and Human Services. (n.d.). Office of dietary supplements - calcium. NIH Office of Dietary Supplements.}
2. _{Campbell, B. J. (2021, August). Healthy Bones at every age. OrthoInfo.}  
3. _{Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, Ross, A. C., Taylor, C. L., Yaktine, A. L., & Del Valle, H. B. (Eds.). (2011). Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press (US).}  
4. _{Calcium. Memorial Sloan Kettering Cancer Center. (2022, July 26).}