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Calcium bioavailability and how much to take

Diverse Calcium opinions


  • Calcium Carbonate is the lowest cost, requires the most stomach acid to be digested, and is probably less bio-available
  • Bio-availability of the Calciums range by perhaps 10X (however, Wikipedia reference below says otherwise)
  • If you must take a lot, take it several times per day – 600 mg at a time
    • As with Magnesium the body can absorb only so much at a time
    • Unsure if there is a 600 mg limit when taking <3,000 IU of vitamin D
    • Vitamin D increases absorption of Calcium: 20% - 50%


  • Calcium sources which do not need stomach acid, such as milk and some plants, are probably the most bio-available
    Not often seniors have less stomach acid, so will not get as much from Calcium Carbonate as younger people

Calcium and Vitamin D category listing has 192 items

Vitamin D Life Opinion: Use a Calcium supplement which has an assortment of Calcium sources (hedge your bets) or plant/animal Calcium

Amazon: calcium plant based supplement 1,000 results Oct 2019
Vitamin D Life is trying a plant-based diet and plant-based Calcium Jan 2020 - experimenting with
Now Supplements, Red Mineral Algae Plus Vitamin D-2, Joint Health*, 180 Veg Capsules $11
VegLife Red Marine Calcium Tablet, 1000 mg, 90 Count $10

PubMed 2181 articles on calcium (absorption OR bioavailability) in title Aug 2020
- interesting items include:


Clipped from WikiPedia March 2011

Calcium supplements are used to prevent and to treat calcium deficiencies. Most experts recommend that supplements be taken with food and that no more than 600 mg should be taken at a time because the percent of calcium absorbed decreases as the amount of calcium in the supplement increases.[18]
It is recommended to spread doses throughout the day.
Recommended daily calcium intake for adults ranges from 1000 to 1500 mg.
It is recommended to take supplements with food to aid in absorption.

Vitamin D is added to some calcium supplements.
Proper vitamin D status is important because vitamin D is converted to a hormone in the body which then induces the synthesis of intestinal proteins responsible for calcium absorption.[29]

  • The absorption of calcium from most food and commonly used dietary supplements __is very similar.[30] (Present Knowledge in Nutrition)

This is contrary to what many calcium supplement manufacturers claim in their promotional materials.__

  • Milk is an excellent source of dietary calcium for those whose bodies tolerate it
    because it has a high concentration of calcium and the calcium in milk is excellently absorbed.[30]
  • Soymilk and other vegetable milks are usually sold with calcium added so that their calcium concentration is as high as in milk
  • Also different kind of juices boosted with calcium are widely available.
  • Calcium carbonate is the most common and least expensive calcium supplement. It should be taken with food. It depends on low pH levels for proper absorption in the intestine.[31] Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk.[32][33] While most people digest calcium carbonate very well, some might develop gastrointestinal discomfort or gas. Taking magnesium with it can help to avoid constipation. Calcium carbonate is 40% elemental calcium. 1000 mg will provide 400 mg of calcium. However, supplement labels will usually indicate how much calcium is present in each serving, not how much calcium carbonate is present.
  • Antacids frequently contain calcium carbonate, and are a commonly used, inexpensive calcium supplement
  • Coral calcium is a salt of calcium derived from fossilized coral reefs. Coral calcium is composed of calcium carbonate and trace minerals.
  • Calcium citrate can be taken without food and is the supplement of choice for individuals with achlorhydria or who are taking histamine-2 blockers or proton-pump inhibitors.[34]
    It is more easily digested and absorbed than calcium carbonate if taken on an empty stomach and less likely to cause constipation and gas than calcium carbonate.
    It also has a lower risk of contributing to the formation of kidney stones.
    Calcium citrate is about 21% elemental calcium. 1000 mg will provide 210 mg of calcium.
    It is more expensive than calcium carbonate and more of it must be taken to get the same amount of calcium.
  • Calcium phosphate costs more than calcium carbonate, but less than calcium citrate.
    It is easily absorbed and is less likely to cause constipation and gas than either.
  • Calcium lactate has similar absorption as calcium carbonate,[35] but is more expensive.
    Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements.[34]
  • Calcium chelates are synthetic calcium compounds, with calcium bound to an organic molecule, such as malate, aspartate, or fumarate.
    These forms of calcium may be better absorbed on an empty stomach.
    However, in general they are absorbed similarly to calcium carbonate and other common calcium supplements when taken with food.[36]
    The 'chelate' mimics the action that natural food performs by keeping the calcium soluble in the intestine.
    Thus, on an empty stomach, in some individuals, chelates might theoretically be absorbed better.
  • Microcrystalline hydroxyapatite (MH) is marketed as a calcium supplement, and has in some randomized trials been found to be more effective than calcium carbonate.

Global Healing Center

  • Calcium Carbonate - cheapest and worst available
  • Calcium Citrate - somewhat better than Carbonate, not as good as CCM. Not need as much stomach acid
  • Oyster Shell Calcium
  • Calcium Gluconate
  • Calcium Lactate
  • Calcium Phosphate
  • Calcium Citrate Malate
  • Calcium Orotate

TrueStarHealth review of the research of Calcium Bioavailability

no reference later than 1995, so probably not up to date

All of the above types and Microcrystalline hydroxyapatite

Good up-to-date overview from Arizona Jan 2011

Clip – – – –
Calcium Phosphate, Calcium Lactate, and Calcium Gluconate have very small percentages of elemental calcium in each supplement tablet.
Therefore it is necessary to take a large number of tablets to consume an adequate amount of calcium every day.

Calcium Citrate 21% element
Best absorbed supplemental form of calcium.It does not require the presence of extra stomach acid to dissolve.
Calcium citrate can come in colloidal form.This is a liquid form of calcium that may be less irritating to the intestinal wall.

Calcium Carbonate 40% element
Most common type of calcium supplement on the market.
Usually requires extra stomach acid for digestion, so should be taken with a meal.

GoodnessDirect March 2009 or 2004?

The inorganic forms:

  • Calcium sulfate
  • Calcium phosphate
  • Calcium carbonate 5-10% absorbed

The organic forms:

  • Calcium gluconate
  • Calcium lactate
  • Calcium citrate 30 to 35%, absorbed
  • Calcium amino acid chelates 65-80% absorption
  • Calcium orotate 90-95% absorbed, but expensive
  • Calcium aspartate
  • Calcium ascorbate

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Endocine Web June 2011

Citrate was found to aid in building bones


See also Vitamin D Life

see wikipagehttp://www.vitad.org/tiki-index.php?page_id=1936

released Nov 30, 2010

See also Web

Calcium bioavailability and how much to take        
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6337 Molecular aspects of Calcium.pdf PDF 2015 admin 13 Jan, 2016 16:00 986.71 Kb 1268
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