- 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
VitaminDWiki 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
PubMed 2044 articles on calcium (absorption OR bioavailability) in title Jan 2016 - interesting items include:
- Dietary and pharmacological compounds altering intestinal calcium absorption in humans and animals Dec 2015
- A comparative study of calcium absorption following a single serving administration of calcium carbonate powder versus calcium citrate tablets in healthy premenopausal women. April 2014
Carbonate (4.25) slightly more than Citrate 4.16  Download the PDF from VitaminDWiki
- Molecular aspects of intestinal calcium absorption June 2015
Download the PDF from VitaminDWiki
Has chart of Calcium absorption and Hormones
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.
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.
- The absorption of calcium from most food and commonly used dietary supplements __is very similar. (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.
- 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. Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk. 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.
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, but is more expensive.
Calcium lactate and calcium gluconate are less concentrated forms of calcium and are not practical oral supplements.
- 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.
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.
- 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
All of the above types and Microcrystalline hydroxyapatite
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?
- Calcium sulfate
- Calcium phosphate
- Calcium carbonate 5-10% absorbed
- 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
- - - - - - - - - - - - - - - -
Endocine Web June 2011
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- All items with Calcium in VitaminDWiki
- Calcium from food or supplements associated with more deaths (US Cohort of 31,000 people) – April 2019
- More Calcium absorbed with more vitamin D – 6.7% more with 4000 IU – RCT March 2014
- Decrease Calcium and Increase Magnesium when increasing vitamin D
- Calcium supplements proven to NOT reduce fractures, but are proven to INCREASE heart problems – July 2015
- More than 1.4 grams of Calcium increased male death rate by 1.4 X – Sept 2018
- 10,000 IU of Vitamin D is too much if you also take Calcium supplements – RCT Sept 2018
- Calcium Essential to Limit Osteoporosis but Avoid Excess, Say Europeans - Nov 2017
- Hypercalcemia can result from excess Vitamin D (if not reduce Ca or increase water) Oct 2016
- Must balance co-factors when increasing vitamin D 500 Ca, 500 Mg - which has the following concept graph
- The Calcium Supplement Problem: As Serious As A Heart Attack Jan 2012
5 clinical trials: taking elemental calcium supplements of 500 mg or more increased the relative risk of heart attack by 27%.
- Controversy: Too much Calcium if increase Vitamin D
some say major problem with just 2,000 IU of vitamin D, others say no problem with 10,000 IU
- Calcium from Chocolate-Calcium chews
Chocoate actually result in DECREASING the amount of Calcium in body or bone density. Not a problem with Chocolate augmented with Calcium
- Vitamin D monotherapy reduces colorectal cancer but has calcemic side effects – April 2013
- IoM again fails to look at interactions - Nov 2010
has the graph: dangerous to have too much Calcium while having lots of vitamin D
- Calcium absorption increased only 6 percent for high amounts of vitamin D – RCT Aug 2012 conflicts with previous understanding
- Little change in Calcium absorption when taking 400 vs 4,000 IU of vitamin D – Oct 2012
- Death by Calcium, book by Thomas Levy – Dec 2013
- Google Search of web for "bioavailability of calcium in milk" 12,200 items as of Nov 2011 - such as the following
- NIH Calcium in Food
- Worlds Healthiest Foods - Calcium
- Healthy Eating club - Calcium
- Stoned To Death: Calcium Supplements Proven To Kill Again May 2012 by Green MedInfo had the following great observation by a reader
It is equally ridiculous and nonsensical to believe that taking calcium pills builds bones, as it is to believe that drinking protein drinks builds muscle.
- The Calcium Supplement Problem: As Serious As A Heart Attack Green Med Info Jan 2013
Meta-analysis of 500+ mg of Calcium supplements increased heart attacks by 25%.
Later Meta-analysis, which included vitamin D, found 24% increase in heart attacks wiht the combination
- A home test kit for excess Calcium in the urine is available $10 for 10 tests
- Calcium Supplments at Consumer Labs
Excellent review of Calcium supplements - but must pay to see all of their content, they do not sell reviews separately
cost per 500 mg Calcium per day ranges from $0.04 to $2
- 12,000 DOCTORS URGE THE USDA TO STOP RECOMMENDING DAIRY March 2019
- Too many people are lactose intolerant and dairy adds cholesterol (which is not really a problem)
- Physicians Committee for Responsible Medicine
- "Research shows that dairy products have little or no benefit for bones. A 2005 review published in Pediatrics showed that drinking milk does not improve bone strength in children"