Bones are a mineral depository in your body, storing 99% of body calcium, 85% of phosphorus, and 60% of magnesium. Only 1% of total body calcium is in the blood. Calcium is required for nerve impulse transmission, muscle contraction, to stabilize a number of proteins and enzymes optimizing their activities, for secretion of hormones like insulin, and for blood clotting.

When calcium level in the blood drops below normal, the parathyroid hormone (PTH) stimulates vitamin D, which in turn, increases the calcium absorption from the small intestines. Vitamin D with PTH also activate the osteoclasts cells to break down the bone tissue, pull out its mineralized matrix to release minerals for transferring them in the blood. This process is called bone resorption, which takes place when, for example, we consume excessive amounts of meat or cheese: our body needs a significant increase of calcium that neutralizes the acid formed from digesting animal protein. When blood calcium climbs to normal levels, the parathyroid glands stop secreting PTH, and the kidneys start excreting any excess calcium in the urine.

Consuming enough calcium is important in maintaining a sufficient level of calcium in blood and bones. If it is below normal, it can imply that your parathyroid gland’s function is low since our skeleton stores a sufficient amount of calcium to maintain the blood calcium level, or you have vitamin D deficiency, or that magnesium blood level is low (which happens in alcoholism). These deficiencies can lead over time to a low bone mineral density (BMD), osteoporosis, and risk of bone fractures.  The BMD level is measured through the DEXA test, similar to an X-ray; and the calcium blood level rather shows the amount of calcium circulating in the blood.

The following calcium intake is recommended by the Institute of Medicine:

Age Ca mg./day
Infants 0-6 months 210
Infants 6-12 months 270
Children 1-3 yr. 500
Children 4-8 yr. 800
Males and Females   9-18 yr. 1,300
Males and Females  19-50 yr. 1,000
Males and Females ≥ 51-70 yr. 1,200
Pregnancy and Lactation  ≤18 yr. 1,300
Pregnancy and Lactation  19-50 yr. 1,000

It is believed that vitamin D3 of 700-800 IU along with 1,200mg of calcium daily maintains normal bone turnover in healthy people during the winter. It prevents osteoporotic bone loss and fractures in 50-70-yr-old people, and it reduces the risk for colorectal cancer in men and breast cancer in premenopausal women by 40 to 50%.

All the above recommendations are based on the hypothesis that calcium may prevent osteoporosis, and there are studies that show that consuming calcium increases bone mass and bone strength. However…

In all countries where the most calcium is consumed, the hip-fracture rates are the highest.

This comes from the international statistics based on the analysis of the food people eat in certain countries from the day they’re born until day they die, and how often elderly people in that country break their hip. Interestingly, these rates are not dependent on the percentage of the elderly in a country.

As our body age, our cells wear out and constantly have to replicate to replace the old ones.  For example, skin and bone cells age because the number of times they can be renewed is limited. That means the faster they age, the sooner their renewal capacity will be exhausted.  Skin cells age due to exposure to chemicals and sunlight that dehydrate the outer cells, thus stimulating the replacement of the cells that have died.  Bone-cells age due to the calcium they have to process and due to the strain they have to sustain.  Therefore, the more calcium they have to process or strain to sustain, the more bone cells die, thus accelerating the renewal of these cells.

Why Processing Too Much Calcium Can Cause Osteoporosis?

The absorption of calcium requires the activity of the osteoblasts cells that create bone and compose a precalcified bone-matrix, upon which the calcium can precipitate. If more calcium is absorbed into the bones, the production and activity of both osteoblasts and osteoclasts is increased. If much calcium is absorbed, much calcium is deported. But then 50 to 70% of the composing osteoblasts die in the composition of new matrix, which means the more osteoblasts activity is stimulated, the more they die.

Since a cell can be replaced only a fixed number of times, the replicative capacity will be exhausted sooner if much calcium is absorbed daily. And if replacement capacity is exhausted, there will be a lack of new osteoblasts. And since only these osteoblasts can compose bone-matrix, then too little of the new bone-matrix can be composed. However, without the matrix the calcium cannot precipitate, and new bone cannot be composed, while old bone is constantly being decomposed anyway to be replaced by new bone. Since there is a lack of precalcified bone matrix upon which to build, replacement cannot occur, and the porous holes will begin to appear. And this is exactly what happens in bones in osteoporosis: there is less of matrix available that can yet be calcified than in the healthy bones. In osteoporosis, dead cells cannot be replaced and micro-fractures cannot be repaired.

The nature is wise, so our body normally absorbs just as much calcium from our food in the intestines as it needs. Only about 200 mg is absorbed into the blood on the average, whether we consume 400 mg or 800 mg calcium daily, or, sometimes, up to 1200 mg. Thus, when we consume more of calcium its absorption rate decreases. However, the absorption rate cannot be continuously and sufficiently decreased, so consequently, about 5% of dietary calcium above the daily 1500 mg will yet be absorbed into the blood if we consume too much calcium.  A study of a group of girls has shown that calcium absorbed into their blood has doubled after they ingested 5-fold amount of calcium.

The food source of calcium has changed during human evolution. Prehistoric man got calcium from roots, tubers, nuts, and beans in amounts exceeding 1500g per day when consuming food in the quantities sufficient to meet the caloric demands of a 6’-tall hunter-gatherer. After people domesticated grains, calcium intakes decreased substantially because the staple foods became grains that are fruits, basically, which is the part of a plant that accumulates the least calcium.

In Western society, U.S., the bulk of calcium for the adults’ diet comes from dairy food and less than third from other sources:

  • Milk and other dairy products – about 72%
  • Grain products − about 11%
  • Food fortified with calcium such as breads, cereal, pasteurized juices, soy and rice beverages, and spreads and margarines
  • Edible plants such as nuts, seeds, vegetables, legumes, and fruit − about 6%
  • Supplemental pills or capsules

Calcium from Milk, Plant Sources, and Supplements

We have been told that drinking plenty of milk builds strong teeth and bones. However, the U.S., which has the greatest consumption of dairy products in the world, demonstrates the highest incidence of bone fractures and osteoporosis in the world. In the January 1988 Journal of Clinical Endocrinology and Metabolism scientists reported that calcium excretion and bone loss increased in a proportion to the amount of animal protein ingested. Animal proteins, due to their high-sulfur content, change the kidney’s reabsorption of calcium; therefore, more calcium is excreted on an animal-based diet such as meats, eggs, and dairy products. People on high-protein diets excrete 90-100 mg. of calcium a day. This means that lifetime effect of extra-calcium from the dairy consumption could be detrimental.

In U.S. pasteurized-milk and cereal-based economy, manufacturers have developed calcium-fortified products they believe are helpful for the individuals who do not get enough calcium from sources other than milk and cereal. Although, calcium absorption varies inversely with load, it is similar in various dairy products is similar and it’s about 28-30%.  So a cup of milk that contains 300 mg of calcium has about 93 mg. of absorbable calcium, i.e., 28-30%. For a comparison, half-a-cup of almonds’ calcium is equal to a cup of milk calcium, or 1.75 cups of kale, with its 58.8% of calcium absorption rate also equals to a cup of milk. Spinach calcium’s absorption rate, on the other hand, is only about 5%.

The absorption rate of calcium, or its bioavailability, is what we think of when seeking for our calcium sources. It depends upon many factors such as presence of other non-nutrient substances in our food such as oxalates, phytates, purines, protein, caffeine, salt, etc., which bind calcium making it unabsorbable and promote its loss with urine. The bioavailability of calcium also depends on how small are the fractions of the supplemental pills you take a few times a day instead of taking the whole pill at once. It also depends on your stomach acidity, type of food you ingest with your calcium supplement (citrus juices promote calcium absorption), or whether you get your calcium from the whole food as opposed to supplements, and other factors such as level of estrogen in women.

From most of the supplemental calcium and food sources calcium is absorbed at about the same rate, as from the dairy products i.e., about 30%. Manufacturers of calcium supplements and books on biochemistry tell that, among supplements, the absorption of calcium-citrate-malate (CCM) supplement is better than that of other salts. However, others suggest that calcium is better absorbed from the whole foods, vs. from the isolated supplemental, which may produce more positive effects on bone health. (See the details on absorption at

What is it the – “Not Organic” Dairy or Meat?

Raw and organic milk that people used to drink from pasture-raised-and-fed animals about 50-70 years ago was a better source of calcium than the contemporary milk. In US today, all milk is sold pasteurized at up to 161º F to kill disease-causing organisms in it. Pasteurizing and homogenizing, however, destroys a wide variety of enzymes in milk essential for the absorption of calcium and other biomolecules crucial to human health such as a few B vitamins and vitamin C. It also reduces the quality and digestibility of milk’s important protein called casein. As a result, processed casein that turns into indigestible hard glue (used in furniture production) becomes a source of allergic reactions associated with a number of diseases.

Grain Diet for Cow

Not organic means that is NOT produced on pastures and with grass, but in stalls, pens, and feedlots of the landless plants, in extremely high-stocking density of the industrial factory farming that started in U.S. before the WWII.  Your milk, yogurt, cheese, and meats come from cows that are fed a diet of highly concentrated grain – barley, GMO corn, and GMO soy, instead of grass and hay they used to eat for million of years. As a fact, cows have horrible stomach diseases on such a diet.


Cows receive antibiotics with their grain feed (70% of all antibiotics produced in U.S are fed to animals) throughout their life to stimulate their rapid growth, which caused the surge of the antibiotic-resistant bacteria.


A synthetic hormone, Recombinant Bovine Growth Hormone (rBGH), produced by genetically engineered E. coli, is implanted into livestock, which is a legal practice in US and Canada.  It is implanted into cows to produce seven to eight more pounds of milk per day in addition to what they are able to naturally produce and to speed up body growth of the animals – their carcass and muscles for meat.  A number of meta analysis showed and the European Union concluded that an 11%-16% increase in the milk production raises risk of cows’ clinical mastitis to 25%, a reduction in fertility to 40%, clinical signs of lameness to 55%, and injection site reactions.

Animal-Derived Diet for Cow

In addition to the implanted rBGH, animals are fed a dry-powder product made of rendered inedible byproducts (including slaughter floor waste with rBGH in it, along with the feces). That means that a part of cows’ diet is the cows themselves, which is the cause of mad-cow disease.  It also means that the recycled rBGH ends up entering the cows once more, doubling the rBHG accumulation in milk and meat, and, therefore, in our body, in our pets food, in the farmed fish, and other animals that are also fed with the dry-powdered animal-waste matter.

What is the rBGH in Milk in Meat?

Well… the rBGH milk is laden with high levels of a natural growth factor (IGF-1) that impedes natural defense mechanisms against early submicroscopic cancers and it is linked to breast, colorectal, and  prostate cancers as it was shown by Edward Giovannucci, Jing Ma, and their colleagues from the University of Harvard studies, and in other experiments. A review cited by Linus Pauling Institute stated that seven out of 14 case-control studies and five out of 9 prospective cohort studies discovered a significant positive association between prostate cancer and some amount of dairy product consumption.

A number of studies concluded that the rBGH in the industrial and domestic sewage is one of the contributors to the estrogenic compounds buildup in the environment, which is believed may explain falling sperm counts in men and premature maturation in girls. Recent studies have found elevated levels of synthetic growth hormones in feedlot wastes, which, eventually, wind up in the waterways downstream to rivers and ocean. No wonder scientists have discovered fish exhibiting abnormal sex characteristics and continuous feminization of male fish.  Researchers in Colorado have made a startling discovery of fish, apparently male, that are developing female sexual organs because of too much estrogen in the water.

Read your dairy products labels: when your milk or cheese is labeled “NO rBGH”, it means the dairy product is free of rBGH and excess levels of IGF-1.  Cheeses imported from Europe are safe since Europe has banned rBGH.  If dairy products are not labeled “Free from antibiotics”, they most likely contain them.

Plant Sources of Calcium

Some authorities believe that vegans have a higher risk of calcium deficiency because calcium in plants is bound with the phytates, oxalates, fibers, or metals. Such belief is not well grounded because most of plants, though containing smaller amounts of calcium, have it 30% bioavailable (means absorbable) as the milk’s calcium is (see the tables for a comparison).  However, most people in the U.S. and Europe do not consume the recommended amounts of either vegetables or calcium as a recent research had shown.  Therefore, it was investigated whether the bitter taste of calcium in vegetables contributes to our rejecting them. They found a strong correlation between the calcium content of 24 vegetables, based on USDA Nutrient Database values, and their bitterness based on the average ratings of 35 people testers.  For another, next experiment on feeding mice and rats, the scientists prepared bitter collard greens as a vegetable with the highest calcium and a sweeter vegetable cabbage as a low-calcium vegetable.

This experiment have shown that mice and rats with a specific appetite for calcium (e.g., those with calcium deficiency) ingested relatively more of the bitter, high-calcium collards (vs. cabbage) than did “normal” mice, or the nutritionally-and-calcium-satiated control rats.  These findings suggest that rodents can detect calcium in vegetables and adjust their behavior accordingly.  The results raised the possibility that humans, like rodents, can also detect calcium in vegetables because of their bitterness, therefore, not liking eating vegetables.

Some other “bitter” compounds in vegetables such as vitamins riboflavin (B2), thiamin (B1), E, and K are found to be less bitter in vegetables than the high calcium.  It was observed that people with different sensitivity to bitter-taste compounds in food (not-calcium related) rate the vegetables acceptability differently.

Because vegetable uptake of calcium from the soil differs in different geographical regions, climate, seasons, and the availability of calcium in the soil, the USDA Nutrient Database values of calcium could be quite different compare to the actual calcium content (and its taste) in a concrete vegetable.

Our sensory power, thus, determines the foods we buy most frequently. That is why the potatoes, carrots, and cauliflower are the most popular vegetables consumed in the U.S., which are also among the lowest in calcium content and in their bitterness. On the contrary, vegetables such as bitter melon, dandelion leaves, and collard greens regarded as the most bitter and as having the highest calcium content.

Examine all the blog’s tables displaying a wide variety of plant sources of calcium such as nuts, seeds, legumes, and vegetables to satisfy your taste buds and daily needs in calcium. Moreover, plant-based foods have more moderate levels of protein, including those with no sulfur-containing amino acids (that bind calcium), with a better calcium-to-phosphorus ratio, making their calcium easier to absorb, and their protein less of a threat to the body’s calcium stores.

See tables with calcium values at and other tables.
See more details on calcium absorption at

Marta Tereshchenko


1.  “Assessment of Feminization of Male Fish in English Rivers by the Environment Agency of England and Wales”  – research article by Melanie Y. Gross-Sorokin, Stephen D. Roast, Geoffrey C. Brighty

Ecosystems and Human Health, Science Group, Environment Agency, Wallingford, Oxfordshire, United Kingdom

2. “Vitamin D and Calcium Insufficiency-Related Chronic Diseases: an Emerging World-Wide Public Health Problem

by Meinrad Peterlik, Steven Boonen, Heide S. Cross, and Christel Lamberg-Allardt

Department of Pathophysiology, Medical University of Vienna, Waehringer Guertel 18–20, A-1090, Vienna, Austria; Center for Metabolic Bone Diseases and Division of Geriatric Medicine, Leuven University, Universitaire Ziekenhuizen, Herestraat 49, B-3000, Leuven, Belgium; Department of Applied Chemistry and Microbiology, Calcium Research Unit, University of Helsinki, Agnes Sjobergin katu 2, F-00014 Helsinki, Finland.

3. “Elevated levels of IGF-1 receptor convey invasive and metastatic capability in a mouse model of pancreatic islet tumorigenesis”

Theresa Lopez and Douglas Hanahan1,

Department of Biochemistry & Biophysics and the UCSF Diabetes and Comprehensive Cancer Centers, University of California, San Francisco, San Francisco, CA 94143 USA

4. “Growth Factor Raises Cancer Risk        ‘

By William J. Cromie

Harvard University Gazette Archives

5. “The contribution of dietary purine over-consumption to hyperuricosuria in calcium oxalate stone formers”

Fredric L. Coe , Edith Moran and Allen G. Kavalich

Renal Division, Department of Medicine, Michael Reese Hospital and Medical Center and Department of Medicine, Pritzker School of Medicine, University of Chicago, Chicago, IL 60616, U.S.A.

6. (fish male with female features)