Calcium Salts according to their Bioavailability

Calcium Salts according to their Bioavailability

What are the most bioavailable Calcium Salts?

Why do we have to take calcium as salt?

Why not just plain calcium?

The forms of calcium available in the market are never pure ionic calcium (Ca2+). In fact, they are always sold as salts, like calcium citrate [(C6H6O7)2Ca3·4H2O].

Above all, this is due to the fact that calcium is a mineral with an electric positive charge which has to be corrected to keep its charge neutral.

Let me give you a simpler example, table salt: Na+Cl-.

Like sodium, it has a positive charge that becomes stable with the chloride molecule, which has a negative electric charge. The same thing happens in the body. This phenomenon is known as “anion gap” and it maintains a neutral electric charge of elements with an uneven valence.

Anion gap formula

Figure VI. Anion gap formula to maintain a neutral electric charge.

The salts that bind calcium and other complexes are meant to improve the solubility and stability, the osmolality, absorption…

But, as you may have imagined: different salts means different properties, right? Exactly!

Are some salts better than others?

A big mistake made by customers is to think that a salt has different effects than other:

“…calcium carbonate is better for the bones and calcium citrate for the functioning of the cells…”

No! The salt only determines the kinetics of the mineral in the body as well as some organoleptic properties.

But, the salt has already been split when it reaches the blood. Moreover, the effects always come from the same compound, calcium, regardless of its form.

We have to take two criteria into account when choosing a salt of any mineral:

Elemental content

It is the fraction of the whole salt that corresponds to the mineral itself.

Let me explain:

When the salt is formed it does not have a 1:1 ratio. Sometimes, the ratios are different in order to reach the properties we were talking about. Therefore, some calcium salts like the citrate contain a 21% of elemental calcium. Others, like the gluconate, will only have a 9%.


It is the ability of our body to absorb calcium salts.

The higher it is, the better. Consequently, we will excrete less mineral and a higher percentage will reach our bloodstream.

Even though sometimes the bioavailability is expressed with exact numbers, it will highly depend on intrinsic and extrinsic factors. Therefore, it is much better to classify the bioavailability as (high/medium/low).


Both factors need to be assessed according to our circumstances in order to determine which one is better, because:

A salt with a very high calcium content (50%) but a poor bioavailability can be worse than a salt with a lower calcium content (20%) but a high bioavailability.

In addition, a worse bioavailability means more gastrointestinal problems. That is why I suggest looking for a highly bioavailable source and then look at its elemental content.

What are the Calcium Salts?

There are many formats of calcium available in the market, let’s review the most common ones and mention their pros and cons:

  • Calcium Carbonate


    • Very cheap.
    • High elemental content.
    • Good bioavailability.


    • It requires an acid medium to be absorbed.
    • Bad absorption:
    • On an empty stomach.
    • People with bowel inflammatory diseases.
    • Patients who use proton pump inhibitors (like omeprazole) or fruit salts regularly (hypochlorhydria).
  • Calcium Citrate


    • Good amount of elemental content.
    • Maximum bioavailability.
    • It is absorbed regardless of the stomach medium (even if it is basic).


    • Slightly more expensive than carbonate.
    • Available in capsules or tablets, the amount we have to consume in order to reach an effective dose can be very high.
  • Coral calcium


    • Same as carbonate


    • Same as carbonate and:
    • It is much more expensive.
    • Those who have created campaigns to “lure” customers to this format have been legally prosecuted.

    Spoiler: Choral calcium is calcium carbonate.

  • Calcium Lactate


    • Good bioavailability (comparable to carbonate).
    • Good solubility.


    • Low elemental content.
  • Calcium Gluconate


    • Good bioavailability (when compared to carbonate).
    • Good solubility.


    • Very low elemental content.
  • Calcium Acetate


    • Cheap.
    • Good elemental content.
    • It can be absorbed regardless of the medium.


    • Little research in humans.
  • Calcium Chloride


    • Good elemental calcium content.


    • Designed for intravenous infusion.
  • Tricalcium Phosphate


    • High elemental content.


    • Moderate bioavailability.
    • Great elimination in the organism by binding to phosphates.
    • Bad solubility.
It is important to highlight that despite all the calcium salts available in the market, there are only two that are actually worth it.

Calcium Citrate and Calcium Carbonate

Which one you will choose will depend on your conditions and the format of the product:

Calcium Citrate

In general, calcium citrate is superior to calcium carbonate, even though it has half its elemental content. Its bioavailability is very high thanks to its combination with citric acid, which means that it will not require an acid medium for its absorption.

Calcium Carbonate

It is better in cases of chronic renal failure due to its ability to bind to phosphate and good renal excretion. Moreover, it has a high elemental content, even though we need to take it with food in order to make the most of it.


SaltElemental ContentBioavailabilityNotes
Calcium carbonate40%High– Useful in chronic renal patients.
– It has to be taken with food.
Calcium citrate21%High– Useful for bowel patients.
– Take it on an empty stomach and patients with hypochlorhydria.
– It does not increase the risk of renal lithiasis in healthy people.
Calcium lactate13%High– Low elemental content.
– Little practical use.
Calcium gluconate9%High– Low elemental content.
– Little practical use.
Calcium Chloride27%High (intravenously)– Clinical use.
– Low elemental content.
Calcium acetate25%High (needs research)– Potential to become an option to consider.
– Lack of research in humans.
– Little practical use.
Tricalcium phosphate38%Moderate– Lower bioavailability than other options.
– More expensive.

New Calcium Citrate by RawSeries

The biggest problem reported by the clinical literature is that calcium citrate has half the elemental content of carbonate. Moreover, it is hard to use since patients need to take many tablets to meet the recommended dose.

Powder format

That is why HSN has come up with a RAW citrate powder, so that you will be able to meet your calcium requirements with this comfortable powder format. Therefore, you will not need to swallow many tablets, which can be a nuisance for many customers:

Calcium citrate by RawSeries

Figure VII. Calcium Citrate by RawSeries.

Higher bioavailability

We bring you the best from the calcium formula with the highest bioavailability in the market. With the best format so that you will easily reach an effective dose without having to take a lot of tablets.


Figure VIII. Jaime Hidalgo using a product by RawSeries.

High solubility

The solubility of this calcium salt is good, it allows us to standardized the blend in water at room temperature without having to excessively dilute it. Moreover, you can take it on an empty stomach since it does not affect its absorption.

You can even mix it in your protein shake and you will not even notice it is there!

Suitable for vegans

Evidently, the product is suitable for vegetarians and vegans.

This is a huge advantage, since people who do not eat dairy products tend to not take enough calcium than what is actually recommended.


Moreover, it does not contain gluten, egg, soy, fish or nuts. Consequently, it is an excellent option for people who have allergies, intolerances and/or sensitivity to these ingredients.

A completely versatile option for anyone and everyone, regardless of their circumstances.


  1. Balk, E. M., Adam, G. P., Langberg, V. N., Earley, A., Clark, P., Ebeling, P. R., … Dawson-Hughes, B. (2017). Global dietary calcium intake among adults: a systematic review. Osteoporosis International, 28(12), 3315–3324.
  2. Ross, A. C., Manson, J. A. E., Abrams, S. A., Aloia, J. F., Brannon, P. M., Clinton, S. K., … Shapses, S. A. (2011). The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: What clinicians need to know. Journal of Clinical Endocrinology and Metabolism, 96(1), 53–58.
  3. Straub, D. A. (2007). Calcium supplementation in clinical practice: A review of forms, doses, and indications. Nutrition in Clinical Practice, 22(3), 286–296.
  4. Wasilewski, G. B., Vervloet, M. G., & Schurgers, L. J. (2019). The Bone—Vasculature Axis: Calcium Supplementation and the Role of Vitamin K. Frontiers in Cardiovascular Medicine, 6, 6.

Related Entries

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Calcium Salts Review

Types - 100%

Benefits - 100%

Cons - 100%

Bioavailability - 100%

Mineral content - 100%

Calcium Citrate - 100%


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About Alfredo Valdés
Alfredo Valdés
He is a specialist in metabolic physiopathology training and in the biomolecular effects of food and physical exercise.
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