Calcium Absorption - Find out The Truth
Arguably the leading Calcium researcher in America is Dr. Robert Heaney of Creighton University with more published papers on Calcium absorption than any other author. Dr. Heaney, an independent University research scientist, has tested dozens of calcium forms over the years and has found most to have acceptable absorption. Contrary to popular marketing hype, published studies show most Calcium supplements today are about 30% absorbed.
In a recent Journal of Nutrition article Heaney discusses “the usually exaggerated marketing claims of superior performance of one (Calcium) salt relative to another”, saying “this emphasis seems inappropriate and misdirected from both cost-benefit and nutritional considerations”(6). In other words, calcium bio-availability is constantly presented as a bigger problem than it really is by calcium manufacturers eager to demonstrate a market advantage. (1-15)
The Big Kidney Stone Fallacy
Many claim that any calcium supplement which is not completely absorbed contributes to kidney stones is based on very old, and highly speculative information which has long since been refuted over and over. In fact the very opposite is true – unabsorbed Calcium prevents kidney stone formation!
Many recent studies show that the free calcium which is not absorbed combines with oxalates and other toxins, so it is very helpful for cleaning up the blood and PREVENTING kidney stones.
Discussing calcium and kidney stones, Professor Robert Heaney says “…nutritionally, there seems to be very little advantage to improving absorbability because unabsorbed calcium exhibits valuable functionality in it’s own right. Calcium remaining in food residue forms complexes with harmful substances left over from digestion, such as oxalic acid, unabsorbed fatty acids and bile acids. This complexation is the mechanism by which high calcium diets reduce the risk of kidney stones and colon cancer.”
Heaney continues “Theoretically, (calcium) sources with high intrinsic absorbability…could meet the body’s skeletal needs for calcium, but they would leave unmet the detoxification function that unabsorbed calcium serves… In brief, there is little or no nutritional advantage to ingesting one’s calcium in a form with absorbability higher than that of natural calcium sources (6)
References
1: Heaney RP, Rafferty K, Dowell MS, Bierman J. Calcium fortification systems differ in bioavailability. J Am Diet Assoc. 2005 May;105(5):807-9.
3: Martin BR, Weaver CM, Heaney RP, Packard PT, Smith DL. Calcium absorption from three salts and CaSO(4)-fortified bread in premenopausal women. J Agric Food Chem. 2002 Jun 19;50(13):3874-6.
4: Heaney RP, Dowell MS, Bierman J, Hale CA, Bendich A. Absorbability and cost effectiveness in calcium supplementation. J Am Coll Nutr. 2001 Jun;20(3):239-46.
5: Heaney RP. Meta-analysis of calcium bioavailability. Am J Ther. 2001 Jan-Feb;8(1):73-4.
6: Heaney RP. Factors influencing the measurement of bioavailability, taking calcium as a model. J Nutr. 2001 Apr;131(4 Suppl):1344S-8S
7: Heaney RP, Dowell MS, Rafferty K, Bierman J. Bioavailability of the calcium in fortified soy imitation milk, with some observations on method. Am J Clin Nutr. 2000 May;71(5):1166-9.
8: Hanes DA, Weaver CM, Heaney RP, Wastney M. Absorption of calcium oxalate does not require dissociation in rats. J Nutr. 1999 Jan;129(1):170-3.
9: Weaver CM, Heaney RP, Martin BR, Fitzsimmons ML. Human calcium absorption from whole-wheat products. J Nutr. 1991 Nov;121(11):1769-75.
10: Heaney RP. Calcium supplements: practical considerations. Osteoporos Int. 1991 Feb;1(2):65-71.
11: Heaney RP, Weaver CM. Calcium absorption from kale. Am J Clin Nutr. 1990 Apr;51(4):656-7.
12: Heaney RP, Weaver CM. Oxalate: effect on calcium absorbability. Am J Clin Nutr. 1989 Oct;50(4):830-2.
13: Heaney RP, Weaver CM, Recker RR. Calcium absorbability from spinach. Am J Clin Nutr. 1988 Apr;47(4):707-9.
14: Smith KT, Heaney RP, Flora L, Hinders SM. Calcium absorption from a new calcium delivery system (CCM). Calcif Tissue Int. 1987 Dec;41(6):351-2.
15: Heaney RP. Calcium bioavailability. Bol Asoc Med P R. 1987 Jan;79(1):27-9.
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