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Home Learn Using the best form of calcium: Carbonate vs Citrate


Using the best form of calcium: Carbonate vs Citrate

Table of contents

What forms of calcium are there?

In supplements, calcium generally comes in the following forms:

  • Calcium carbonate
  • Calcium citrate

While calcium carbonate is used most commonly in supplements due to its low cost, there’s significant evidence suggesting that calcium citrate is absorbed and used better in the body.

Calcium is one glaring example of a nutrient that has different effects depending on what form it takes. In this quick guide, we’ll cover the different forms of nutritional calcium and explain why we decided to ditch calcium carbonate and start using calcium citrate in our Feel Multivitamin™.

Calcium carbonate isn’t synthetic, but the process that this substance goes through on its way to becoming an edible supplement makes it hard for your digestive system to absorb this form of calcium. At the same time, however, your body needs lots of calcium to maintain your bones and facilitate cellular signalling, and if you have trouble digesting the calcium you consume, the unabsorbed nutrient content could cause health concerns.

Why is Calcium Citrate better than Calcium Carbonate?

While calcium carbonate contains a large amount of elemental calcium, it requires stomach acid to dissolve. Calcium citrate, however, will dissolve on an empty stomach, so it isn’t necessary to take this form of calcium with food. While calcium citrate contains about half the elemental calcium that’s present in calcium carbonate, the fact that this type of calcium digests easier makes it the clear winner in the calcium supplement battle.

Keep in mind that other forms of calcium, such as “coral calcium” or calcium phosphate, either do not have nutritional benefits or are falsely advertised. Calcium citrate and calcium carbonate are the only trustworthy forms of nutritional calcium on the market, and calcium citrate doesn’t cause constipation or any other health issues.


  • Calcium carbonate requires stomach acid to dissolve
  • Calcium citrate will dissolve on an empty stomach.

So why is Calcium Citrate better for me?

If you have inflammatory bowel disease or your stomach doesn’t produce enough acid, using calcium citrate instead of calcium carbonate is an absolute must. Calcium carbonate is wholly dependent on stomach acid to dissolve, and since your stomach only produces acid when you eat, this substance will simply stick around on the inside of your stomach or try to pass through your digestive tract without stomach acid, which could create or worsen digestive issues.

Calcium citrate is the most bioavailable form of calcium, which means that it absorbs much faster and more effectively than calcium carbonate. When your body is able to use close to the entirety of a substance you ingest, there’s less of that substance you have to excrete or process with your internal organs, which reduces strain on your body and improves your overall health.

Plus, there have been some concerns that calcium carbonate supplements might cause heart disease. Due to their high bioavailability and different formulation process, however, calcium citrate supplements appear to eliminate this risk. It’s always a good idea to consult with a doctor before you start taking a supplement, but medical experts around the world agree that calcium citrate is the safest form of calcium that you can take as a supplement.


  • Calcium citrate is the most bioavailable form of calcium
  • Calcium carbonate supplements might cause heart disease
  • Medical experts around the world agree that calcium citrate is the safest form of calcium

Why do we use calcium citrate instead of other forms?

Here at WeAreFeel, your health and happiness are our top priorities. Without enough calcium, your body won’t be able to operate day to day, and your bone density will gradually leach away until you’re at risk of osteoporosis and other bone diseases. With a daily capsule of our Feel Multivitamin™, however, you can keep your bones and cells intact without having to worry about the possible side effects of calcium carbonate. Enjoy your NRV of calcium in your daily Feel Multivitamin and start feeling better from this day forward!

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About the author
Katie Hipwell - Katie is an AfN Registered Nutritionist (RNutr) with a specialism in food and is Head of Nutrition at Feel. Katie has worked in the food supplement industry for 10 years. She has completed a Master's degree in Human Nutrition and an undergraduate degree in BSc Sport and Exercise Nutrition.
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