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High Calcium Absorption

High calcium absorption rates, such as 100%, have never been scientifically proven. Neither has 70%, 80% or 90%.  Most calcium experts consider those levels to be physically impossible. Yet, these very calcium absorption claims are common.
Consider for example, this statement the Coral Calcium Superstore website:

 “The calcium released from Coral Calcium is 100% absorbed as we get 994 mg's of coral minerals in each coral calcium sachet!”

Or these claims of the website of OsteOganical® :

“In fact, whereas a typical form of calcium such as calcium carbonate might achieve 7-8% absorption by the human body, and specially chelated forms of calcium might achieve 30-40% absorption, our unique formula calcium proved to be a stunning 90% absorbable by the human body!”calcium-absorption | Article

Another brand, called Nano Cal/Mag-Ionic Powder® claims it is:

“A proprietary and synergistic blend of calcium gluconate and magnesium carbonate?  Nano Cal/Mag-Ionic is a potent 100% available and absorbable Ionic solution when dissolved in water. This means the moment the drink enters the mouth it begins to be absorbed into the blood stream rapidly working its way to the cell levels.
None of these calcium supplements provide scientific research or published study references to support their absorption claims."

Rates of Absorption
What is a realistic rate of calcium bioavailability?  Published research by Heaney and other suggests that 23 % to 37% represents the range of calcium absorption, among healthy young adults.  Even those figures are subjective because there isn't one definitive measure of absorption.   Absorption is estimated based on modeling techniques, which serve as estimates.

Moreover, the human body can only absorb small amounts of calcium at a time.  According the National Institute of Health Calcium Fact Sheet:

“The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorption decreases. Absorption is highest in doses ≤500 mg. So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day.”

That means that a typical person can only absorb about 150 mg of calcium from a serving of 500 mg in a calcium supplement.  Even if a 100% absorbed calcium supplement existed, most of the calcium may never even reach your bones.

calcium-absorption | ArticleIf calcium absorption is within a 23-37% range, why do brands such as AdvaCAL build bone density more significantly?   Two mechanisms appear to be at play with AdvaCAL.  First, the calcium is more bioavailable than other forms, based on various calcium absorption models.   Second, an amino acid extract in AdvaCAL called HAI appears to modulate or slow parathyroid activity (PTH) in the body.  Accelerated PTH activity has been linked to bone loss.  No other calcium supplement but AdvaCAL has HAI™.

Absorption claims are overdone and inexact.   A better approach may be to examine the published research on various calcium pills in increasing bone density.  That may be a more scientifically sound way to help reduce the risk of bone loss long term.  But again, rely on published science, not selected testimonials. Consider only those calcium or other nutrients with multiple medical journal research studies showing benefits – whether in bone building or calcium absorption.