Build them bones! The U.S. is the country that consumes the most amount of dairy products yet it has the highest osteoporosis rate.. What does that tell you?
Factors that Inhibit Calcium Absorption
Ron Hoggan & Don Wiss
We focus on supplementing our diets with calcium, but we don't stop to
question why so much of the calcium we consume is wasted. Normally, we only
absorb about 10% of the calcium we ingest (1). A focus on the dynamics that
impact on calcium absorption may therefore be more profitable for those who
are concerned about maintaining and building healthy bones.
Among the factors that influence calcium absorption are three major regulators
of calcium metabolism in the body. The parathyroid glands produce
a hormone (PTH) which moves calcium from the bones into the bloodstream. It
also signals the kidneys conserve calcium and other minerals from the
urine. Additionally, PTH signals the kidneys to produce calcitriol, which is
formed from vitamin D, and which, among other functions, signals the small
intestine to absorb more calcium (2). The thyroid gland secretes calcitonin,
which increases bone mineralization, and decreases the rate at which the bone
is broken down.
Any factors which interfere with, or alter the delicate balance maintained
by these body systems are likely to have a negative impact on bone
mineralization. The following twelve items, many of which stem from our
modern diet, are likely, sometimes surprising culprits interfering with
1. A diet high in phytic acid, which is found in the bran of whole grains,
is likely to interfere with calcium absorption. This acid binds to a
variety of minerals including calcium, to form insoluble salts, called
phytates, which are wasted from the body. Probably because grains are a
relatively new food, from an evolutionary perspective, it appears that
we have not yet developed digestive tracts which can break down these
2. A diet high in sodium may also interfere with calcium absorption. Some
researchers believe that dietary sodium levels were extremely low in the
past, compared to modern diets (4) and increased sodium intake can result
in increased calcium excretion (5).
3. Vitamin D is formed by an interaction between the sun's rays, and skin
oils. Without supplementation, we may be at risk of inadequate vitamin D,
if we spend most daylight hours inside. As mentioned earlier, this vitamin
is a regulating factor in calcium absorption. Circulating levels of vitamin
D throughout the year were probably higher in stone age men and women
because they were more likely to be exposed to the sun's rays. There is
evidence suggesting that many elderly in Western countries are deficient
in vitamin D (6). Treating every elderly lady in northern latitudes with
vitamin D tablets is probably not a bad idea.
4. Our sedentary life ways also interfere with mineralizing our bones. Our
ancestors were probably much more active than we are. Impact stress on
bone, as in walking and jogging, tends to increase production of
calcitonin, which leads to increased deposition of calcium in the bones
(7). Exercise induced stress increases the cross sectional area and perhaps
(equivocal data) bone mineral density (8). It is important to note that
cycling and swimming are not as beneficial because these activities are not
as likely to cause calcitonin production.
5. While the modern diet, in the western world, usually contains ample
calcium, it may offer inadequate magnesium. Studies of our ancestors'
pre-agricultural diets indicate that magnesium was probably consumed at
about a 1:1 ratio with calcium (8). Thus, that would be the approximate
ratio our bodies evolved with. As the Ca:Mg ratio is 12:1 in dairy, those
consuming this much vaunted source of calcium might only experience the
equivocal benefit that is reported in the medical literature(9). The Ca:Mg
ratio in post-agricultural diets is about 4:1 (10). Because both calcium
and magnesium compete for the same absorption mechanisms, the imbalanced
intake associated with our modern diet may well lead to magnesium
deficiency. One feature of magnesium deficiency is the inhibition of
osteoblasts which are cells that build and maintain bones. One of the
authors (Ron) increased his bone density significantly by taking magnesium
6. While there is no evidence that high levels of meat consumption are
detrimental, as long as there are adequate minerals in the diet, there
are reports of isolated, fractionated animo acids from milk or eggs, which
have been found to correlate with calcium loss. Some suggest that we should
be especially leery of whey protein.
7. Sugar has been implicated in upsets to the calcium/phosphorus balance.
Melvin Page reported that sugar increases blood calcium through inciting
reabsorbtion from bone tissue (11). A recent rat study is of some relevance.
Although sugar was not implicated in osteoporotic changes, Li et al. found
clear indications of depleted bone density in their animal study of dietary
8. Phosphoric acid, as found in soft drinks, has also been argued to
interfere with calcium absorption (13). In order to utilize calcium well,
in addition to vitamin D, we need 1.5 grams phosphorus and 0.5 grams
magnesium for each gram of calcium. We normally get plenty of phosphorus;
frequently more than enough. Although we need phosphorous, it is abundant
in our diets, and increased intake drives up our requirements for calcium
and magnesium (14) so it is important to limit soft drinks as they contain
considerable quantities of phosphorous and sugar.
9. Coffee reduces inositol levels in the blood. Inositol is a regulating
factor in calcium metabolism. It inhibits formation of the cells
(osteoclasts) that draw calcium from the bones into the bloodstream (14).
It also exerts a direct influence on transport of calcium into cells
10. Although the dynamic is not well understood, tobacco smoking also
appears to interfere with bone mineralization. Some researchers report that
osteoblast formation is inhibited by nicotine (18). Study of animals given
chronic doses of nicotine support this perspective by demonstrating
reductions in bone mass (19). Studies of large groups show reductions in
bone mass of smokers, but there is some debate as to the cause (20).
11. Undiagnosed celiac disease is another cause of calcium depletion of
the bones. Recent blood screening data suggest that 95% of the celiacs in
the USA are undiagnosed. For those who have the condition and are
undiagnosed there is malabsorption of the fat soluble minerals and
vitamins, especially calcium and vitamin D (21). Adult diagnosed celiac
disease is usually associated with at least some degree of reduced bone
density (22). Poorly managed celiac disease is also a risk factor for
osteoporosis. It appears that magnesium supplementation may be more
helpful to celiac patients than calcium supplementation (9, 23). Loren
Cordain has recently published a discussion of human consumption of cereal
grains which delineates the problems associated with human consumption of
cereal grains, whether one has celiac disease or not (24)
12. A diet dominated by acidic foods will tend to raise blood ph which must
be buffered. Calcium is leached from the bones to buffer the blood and keep
it within the ph range required for homeostasis (25).
13. Oxalic acid (found in beans and a variety of vegetables) tends to
inhibit calcium absorption through binding to minerals in the intestinal
If you are concerned about bone mineralization, the above factors which
interfere with calcium absorption suggest the following strategies:
1. Get your fiber from fruits and vegetables, minimizing grain consumption;
2. Minimize your salt intake;
3. Spend regular time in the sun, or supplement with vitamin D;
4. Get plenty of anti-gravity exercise;
5. Ensure that your magnesium intake is adequate;
6. Reduce or eliminate dairy products and eggs from your diet;
7. Reduce your sugar intake;
8. Avoid soft drinks;
9. Avoid coffee and tea;
10. Do not smoke;
11. Get tested for celiac disease and gluten sensitivity.
1. Vander A, _Renal Physiology_ McGraw Hill, N.Y., 1975, p. 123
2. Tortora G, Grabowski S, _Principles of Anatomy & Physiology_ Harper
Collins, N.Y., 1996 p.525
3. Lindeberg S, http://listserv.icors.org/CGI/wa.exe?A2 ... diet&P=850
4. Lindeberg S, http://listserv.icors.org/CGI/wa.exe?A2 ... iet&P=2282
5. Lau EM, et al. Nutrition and osteoporosis. Curr Opin Rheumatol. 1998
6. van der Wielen RP, et al. Serum vitamin D concentrations among elderly
people in Europe. Lancet. 1995 Jul 22;346(8969):207-10.
7. Tortora G, Grabowski S, _Principles of Anatomy & Physiology_ Harper
Collins, N.Y., 1996 p. 1578. Cordain L.
8. http://www.springerlink.com/content/l2h ... pdf?page=1
9. Rude RK, et al. Magnesium deficiency: possible role in osteoporosis
associated with gluten-sensitive enteropathy. Osteoporos
10. Varo P. Mineral element balance and coronary heart disease. Int J Vit
Nutr Res 1974;44:267-73
11. Page ME. Systemic and prosthodontic treatment to prevent bone
resorption in edentulous patients. J Prosthet Dent. 1975 May;33(5):483-8.
12. Li KC, et al. Effects of a high fat-sucrose diet on cortical bone
morphology and biomechanics. Calcif Tissue Int. 1990 Nov;47(5):308-13.
13. Meinig G. http://members.aol.com/ppnf/articles/softdrk.html
14. Lukert BP, et al. Influence of nutritional factors on
calcium-regulating hormones and bone loss.
Calcif Tissue Int. 1987 Mar;40(3):119-25.
15.Choi SJ, et al. Cloning and identification of human Sca as a novel
inhibitor of osteoclast formation and bone resorption. J Clin Invest. 1998
16. Wojcikiewicz RJ, et al. Differences among type I, II, and III
inositol-1,4,5-trisphosphate receptors in ligand-binding affinity influence
the sensitivity of calcium stores to inositol-1,4,5-trisphosphate.
Mol Pharmacol. 1998 Apr;53(4):656-62.
18. Laroche M, et al. [Osteocalcin and smoking]. Rev Rhum Ed Fr. 1994
19. Broulik PD, et al. The effect of chronic nicotine administration on
bone mineral content in mice. Horm Metab Res. 1993 Apr;25(4):219-21.
20. Ernst E. Smoking, a cause of back trouble? Br J Rheumatol. 1993
21. Wiss D, http://www.GFlinks.com/
22. Green P, American Celiac Society Conference "Unmasking Celiac Disease"
23. Hoggan R, http://www.gluten-free.org/hoggan/
24. Cordain L, Cereal Grains: Humanity's Double Edged Sword. World Review
of Nutrition & Dietetics, 1999;84:19-73
25. Cordain L, http://www.thepaleodiet.com/nutritional ... acid.shtml
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