Calcium (Ca)

Brief description

Calcium is the 5th most abundant mineral in the body, more than 99% of which is contained in the skeleton as a complex calcium phosphate molecule. This mineral provides bone strength, movement ability, and plays a role in a wide range of other functions. Calcium is healthy bones, blood vessels, hormonal metabolism, absorption of trace elements and transmission of nerve impulses. Its metabolism is regulated by three main transport systems: intestinal absorption, renal reabsorption and bone metabolism[1].

History of discovery

As early as the 16th century, Dutch doctors concluded that the skeleton is a dynamic tissue, influenced by hormones and capable of remodeling throughout life. Another important discovery in the history of calcium was made about 100 years ago when Sidney Ringer discovered that cardiac muscle contraction was stimulated and maintained by adding calcium to the perfusion fluid. In addition, it has been shown that the action of calcium has an activating effect in other cells of the body.[3].

Calcium rich foods

Indicated approximate availability of mg in 100 g of product[3]:

Daily need

There is no exact estimate of How long calcium to consume each day. Aside from a few exceptions, such as extreme fasting or hyperparathyroidism, circulating calcium levels in the blood remain adequate even with chronic deficiency, as the body uses calcium from bones to maintain health. Therefore, the daily calcium requirement is based on calculations in relation to a healthy population without chronic diseases. In addition, this amount suggests that smaller doses of calcium are sufficient for some people.

During pregnancy, the mother’s skeleton is not used as a reserve for fetal calcium needs. Calcium-regulating hormones regulate the mother’s absorption of the mineral so that calcium intake during pregnancy does not need to be increased significantly. Increasing dietary calcium intake will not prevent the loss of calcium from the mother’s skeleton during lactation, but lost calcium is usually restored after weaning. Thus, the daily requirement for calcium in lactating women is the same as in non-lactating women.

An increase in calcium intake may be considered when:

  • with amenorrhea: caused by excessive physical activity or anorexia, amenorrhea leads to a decrease in the level of stored calcium, its weak absorption, and a general decrease in bone mass;
  • Menopausal: Decreased estrogen production during menopause is associated with accelerated bone loss over 5 years. Low estrogen levels are accompanied by low calcium absorption and increased bone turnover.
  • for lactose intolerance: People who are lactose intolerant and avoid dairy products may be at risk of calcium deficiency. It is interesting to note that even with lactose intolerance, the calcium present in milk is absorbed normally;
  • with a vegetarian or vegan diet: the bioavailability of calcium can be reduced with a vegetarian diet due to the increased intake of oxalic and phytic acids, which are found in many vegetables and beans;
  • when feeding multiple babies: Due to the increased production of breast milk when feeding multiple babies, doctors may consider supplementing calcium and magnesium during lactation[2].

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Useful properties of calcium and its effect on the body

The body of an adult contains about 1200 g of calcium, which is about 1-2% of body weight. Of these, 99% is found in mineralized tissues such as bones and teeth, where it is present as calcium phosphate and small amounts of calcium carbonate, which provides skeletal rigidity and structure. 1% is found in blood, extracellular fluid, muscles and other tissues. It plays a role in mediating vascular contraction and relaxation, muscle contraction, nerve signaling, and glandular secretion.[5].

Adequate calcium intake has many benefits for the body. Calcium helps:

  • to ensure the growth and maintenance of healthy bones and teeth;
  • to support the work of tissues, the cells of which constantly require its supply – in the heart, muscles and other organs;
  • the work of blood vessels and nerves in the transmission of impulses;
  • assimilate such trace elements as vitamins D, K, magnesium and phosphorus;
  • keep the processes of thrombus formation under control;
  • maintain the normal work of digestive enzymes[4].

Calcium is absorbed by active transport and passive diffusion through the intestinal mucosa. Active calcium transport requires an active form of vitamin D and provides most of the absorption of calcium at low to moderate intake levels, as well as in times of urgent need such as growth, pregnancy, or lactation. Passive diffusion becomes more important with sufficient and high calcium intake.

With decreasing calcium intake, the efficiency of calcium absorption increases (and vice versa). However, this increased efficiency of calcium absorption is generally insufficient to compensate for the loss of absorbed calcium that occurs with a decrease in dietary calcium intake. Calcium absorption decreases with age in both men and women. Calcium is excreted in urine and feces[2].

Healthy food combinations with calcium

  • Calcium + InulinInulin is a type of fiber that helps balance the good bacteria in the intestines. In addition, it helps to strengthen bones by promoting calcium absorption. Inulin is found in foods such as artichokes, onions, garlic, green onions, chicory, banana, whole wheat, and asparagus.
  • Calcium + Vitamin DThese two elements are directly related to each other. The body needs a sufficient level of vitamin D in order to absorb calcium[6].
  • Calcium + MagnesiumMagnesium assists in the absorption of calcium from the blood into the bones. Without magnesium, calcium metabolism is practically impossible. Healthy sources of magnesium include green leafy vegetables, broccoli, cucumber, green beans, celery, and a variety of seeds.[7].

Calcium absorption depends on vitamin D intake and status. The effectiveness of absorption is related to the physiological requirements for calcium and depends on the dosage. Dietary inhibitors of calcium absorption include substances that form complexes in the intestine. Protein and sodium can also alter the bioavailability of calcium, as high calcium levels increase urinary excretion. Although the amount absorbed in the intestine increases, the end result may be a decrease in the proportion of calcium used directly by the body. Lactose, on the other hand, promotes calcium absorption.[8].

The absorption of calcium across the intestinal membrane occurs through both the vitamin D-dependent as well as the vitamin D-independent pathway. The duodenum is the main source of calcium absorption, although the rest of the small and large intestine also contributes. Approximately 60-70% of calcium is passively reabsorbed in the kidneys under the influence of a special substance produced during the reabsorption of sodium and water. Another 10% is absorbed in nephron cells[9].

Cooking rules

Numerous studies have been carried out in order to find out how food preparation affects the changes in the amount of minerals and vitamins in food. Like other minerals, calcium is broken down by 30-40 percent compared to raw foods. The losses were especially high in vegetables. Among the various cooking methods, the loss of minerals was greatest when squeezing after boiling and soaking in water after slicing, followed by frying, frying, and braising. Moreover, the results were the same both for home cooking and for mass production. In order to minimize the loss of calcium during cooking, it is advised to eat boiled food with broth, add a small amount of salt during cooking, do not overcook food, and choose cooking methods that preserve the beneficial properties of food as much as possible.[10].

Use in official medicine

Calcium is essential for the growth and maintenance of healthy bones and teeth. Research shows that, especially when combined with vitamin D, calcium can reduce the risk of osteoporosis. Osteoporosis is a disease that is influenced by many factors. It is most common among women during menopause. There are several ways to reduce the likelihood of bone damage associated with osteoporosis, including maximizing bone mass and limiting bone loss later in life. For this, calcium is the most important material, and a sufficient amount of vitamin D ensures optimal absorption of calcium in the body.

There are several ways to achieve higher peak bone mass, including practicing sports such as running and strength training combined with adequate calcium (1200 mg / day) and vitamin D (600 IU / day) at a young age. Although exercise such as walking, swimming, and cycling has beneficial effects on health, the effect on bone loss is negligible.

Calcium, like other micronutrients, may have some effect on colon cancer. Adding 1200-2000 mg of calcium per day to the diet has been shown to result in a modest reduction in the incidence of bowel cancer in controlled clinical trials. Participants with the highest calcium intakes (1087 mg / day from food and supplements) were 22% less likely to develop cancer, compared to those with the lowest intake (732 mg / day). In most studies, only a small reduction in risk was noted with calcium supplementation. This can be explained by different reactions to calcium in different people.[4].

Some research suggests that taking calcium supplements may play a role in preventing high blood pressure in pregnant women and preeclampsia. This is a serious condition that usually occurs after the 20th week of pregnancy, in which the pregnant woman develops hypertension and excess protein in the urine. It is the leading cause of maternal and neonatal morbidity and mortality, affecting about 5-8% of pregnancies in the United States and up to 14% of pregnancies worldwide. Research shows that calcium supplementation during pregnancy reduces the risk of preeclampsia, but these benefits are only seen in the calcium-deficient groups. For example, in a randomized clinical trial of 524 healthy women in India with an average baseline calcium intake of just 314 mg / day, 2000 mg daily calcium supplements from 12-25 weeks of gestation to delivery significantly reduced the risk of preeclampsia and preterm labor compared to placebo. … In turn, a similar study in the United States (where daily calcium intake is generally normal) showed no results. The most significant results were in women with a calcium intake of less than 900 mg per day.[11].

It is believed that women who use calcium supplements and choose a balanced diet have a lower risk of stroke over 14 years. However, doctors warn that then the risk of developing cardiovascular diseases increases.[4].

Calcium during pregnancy

Several professional organizations recommend calcium supplements during pregnancy for women with low calcium intake to reduce the risk of preeclampsia. For example, the American College of Obstetrics and Gynecology (ACOG) states that daily calcium supplements of 1500-2000 mg can reduce the severity of preeclampsia in pregnant women who have less than 600 mg / day calcium intake. Likewise, the World Health Organization (WHO) recommends 1500-2000 mg of calcium for pregnant women with low dietary calcium intake, especially those with an increased risk of gestational hypertension. WHO recommends dividing the total daily dose into three, which should preferably be taken with meals, from the 20th week of pregnancy to delivery. WHO also recommends splitting calcium and iron supplements for pregnant women into multiple doses to minimize the inhibitory effect of calcium on iron absorption. But some researchers argue that this interaction has minimal clinical relevance and argue that manufacturers therefore discourage patients from splitting supplements in order to simplify the regimen and facilitate adherence. The Canadian Working Group on Hypertensive Disorders in Pregnancy, the International Society for the Study of Hypertension in Pregnant Women and the Society of Obstetric Medicine of Australia and New Zealand have issued similar guidelines[11].

Calcium in traditional medicine

Traditional medicine recognizes calcium as a very important mineral for the health of bones, muscles, teeth and the cardiovascular system. Many folk recipes are used to strengthen the skeleton – among them the use of eggshells, lactic acid products (for example, the so-called “kefir diet”, in which the patient consumes 6 glasses of low-fat kefir per day to avoid hypertension, diabetes mellitus, atherosclerosis). An increase in calcium intake is also advised for patients with any form of tuberculosis. In addition, folk recipes consider the consequences of excessive calcium intake, such as, for example, kidney stones. With such a diagnosis, it is also advised, in addition to drug treatment, to change the diet. It is recommended to include wholemeal bread in food, avoid refined carbohydrates, sugar and milk[12].

Calcium in the latest scientific research

  • Researchers have found that excess calcium in brain cells can lead to the formation of toxic clusters that are a hallmark of Parkinson’s disease. An international team led by the University of Cambridge has found that calcium may mediate interactions between small membrane structures within nerve endings that are important for neuronal signaling in the brain and alpha-synuclein, a protein associated with Parkinson’s disease. Excessive levels of calcium or alpha-synuclein can cause a chain reaction that leads to the death of brain cells. Understanding the role of alpha synuclein in physiological or pathological processes can help develop new treatments for Parkinson’s disease. For example, there is a possibility that drugs designed to block calcium in heart disease may also have potential against Parkinson’s disease.[15].
  • A new scientific study presented at the American College of Cardiac Science Sessions of the Intermountain Institute of Public Health in Salt Lake City shows that detecting the presence or absence of calcium in the coronary arteries can help determine the risk of cardiovascular disease. Moreover, this study can be carried out not only to determine future diseases, but also when symptoms are already present. The experiment involved 5547 patients with no history of heart disease who presented to a medical center with chest pain between April 2013 and June 2016. They found that patients who had coronary artery calcium on scans had a higher risk of heart attack within 90 days compared to patients who had no calcium on CT. The researchers also found that patients with detected calcium also had more severe obstructive coronary artery disease, revascularization, and / or other serious adverse cardiac events in subsequent years.[14].
  • Eating a diet rich in calcium or consuming it in the form of dietary supplements does not increase the risk of age-related macular degeneration, according to a study by the US National Eye Institute. This condition is the leading cause of vision loss and blindness among people aged 65 and older in the United States. The results were published in the journal JAMA Ophthalmology. These findings contradict earlier research indicating that high calcium levels have been associated with an increased prevalence of age-related macular degeneration, and at the same time prove that calcium, on the contrary, plays a protective role in this case.[13].

The use of calcium in cosmetology

In addition to its key role in the health of bones, teeth and body organs, calcium is also important for the skin. Most of it is found in the outermost layer of the skin (epidermis), where calcium has been shown to be responsible for restoring barrier function and homeostasis (a self-healing process in which the number of cell divisions in the skin compensates for the number of lost cells). Keratinocytes – cells of the epidermis – need calcium concentrations in different ways. Despite the constant renewal (almost every 60 days, the epidermis is completely renewed, replacing more than 80 billion keratinocytes in the body of an adult), our skin eventually succumbs to aging, as the rate of turnover of keratinocytes slows down dramatically. Aging is associated with thinning of the epidermis, elastosis, decreased barrier function, and loss of melanocytes. Since the differentiation of keratinocytes is strongly dependent on calcium, it is also involved in skin aging. It has been shown that the epidermal calcium gradient in the skin, which promotes the growth of keratinocytes and allows their differentiation, is lost during skin aging.[16].

In addition, calcium oxide is used in cosmetology as a regulator of acidity and an absorbent. It is found in products such as makeup, bath salts, shaving foams, oral and hair care products.[17].

Calcium for weight loss

Several studies have suggested that calcium supplementation may help combat obesity. This hypothesis was based on the fact that high calcium intake can reduce the concentration of calcium in fat cells, decreasing the production of parathyroid hormone and the active form of vitamin D. A decrease in intracellular calcium concentration, in turn, can increase the breakdown of fat and inhibit the accumulation of fat in these cells. In addition, calcium from food or supplements can bind small amounts of dietary fat in the digestive tract and interfere with the absorption of that fat. Dairy products, in particular, may contain additional components that have an even greater effect on body weight than would be expected from their calcium content. For example, protein and other components of dairy products can modulate hormones that regulate appetite.

A 2014 randomized crossover study of 15 healthy young men found that diets high in milk or cheese (providing a total of 1700 mg / day of calcium) significantly increased fecal fat excretion compared to a control diet that provided 500 mg calcium / day. However, the results of clinical trials that examined the effects of calcium on body weight were mostly negative. For example, 1500 mg / day supplementation was investigated in 340 overweight or obese adults with mean baseline calcium intakes of 878 mg / day (treatment group) and 887 mg / day (placebo group). Compared with placebo, calcium supplementation for 2 years had no clinically significant effect on weight.

Interesting Facts

  • In its pure elemental state, calcium is a soft silvery white alkaline earth metal. It is important to note, however, that calcium is never found in this isolated state in nature, but instead exists in compounds. Calcium compounds can be found in a variety of minerals including limestone (calcium carbonate), gypsum (calcium sulfate), and fluorite (calcium fluoride). Calcium makes up about 4,2 percent of the earth’s crust by weight.
  • To isolate pure calcium, electrolysis is performed, a technique that uses direct electric current to separate elements from their natural sources. After isolation, calcium becomes quite reactive and upon contact with air forms a grayish-white oxide and nitride coating.
  • Calcium oxide, also called lime, produces bright, intense light when exposed to an oxygen-hydrogen flame. In the 1800s, before electricity was invented, this compound was used to illuminate theaters. From this in English comes the expression “in the limelight” – “to be in the spotlight.”
  • Many nutritionists recommend a 2: 1 calcium to magnesium ratio. But although our body needs more calcium, we are actually more prone to magnesium deficiency. This is because our bodies tend to store and process calcium, while magnesium is used or excreted from the body and must be replenished daily.[19].

Contraindications and cautions

Signs of calcium deficiency

Chronic calcium deficiency can result from inadequate intake or poor intestinal absorption. Also, chronic kidney failure, vitamin D deficiency and low blood magnesium levels can be the cause. During a chronic calcium deficiency, the mineral is absorbed from the skeleton to maintain normal levels of calcium circulation, thereby impairing bone health. As a consequence, chronic calcium deficiency leads to decreased bone mass and osteoporosis. The consequences of calcium deficiency are osteopenia, osteoporosis and an increased risk of bone fractures.[2].

Symptoms of hypocalcemia include numbness in the fingers, muscle cramps, convulsions, lethargy, poor appetite, and abnormal heart rhythms. If not treated promptly, calcium deficiency can be fatal. Therefore, it is very important to consult your doctor if you suspect a lack of calcium.[4].

Signs of excess calcium

The available data on the adverse effects of excess calcium intake in humans comes primarily from supplementation studies. Among the many side effects of excess calcium in the body, the three most studied and biologically significant are:

  • stones in the kidneys;
  • hypercalcemia and renal failure;
  • interaction of calcium with the absorption of other trace elements[2].

Other symptoms of excess calcium include loss of appetite, nausea, vomiting, confusion, and coma.

The limit for calcium intake is 1000-1500 mg / day in infants, 2,500 mg / day in children 1 to 8 years old, 3000 mg / day in children 9 years old and adolescents through 18 years old. In adults, the norm is 2,500 mg / day, and after 51 years – 2,000 mg / day.[4].

Interaction with other elements

  • Caffeine. Caffeine can increase urinary calcium loss and decrease calcium absorption. It should be noted that the effect of caffeine remains relatively moderate; this effect was primarily observed in women who did not consume enough calcium during menopause.
  • Magnesium. Moderate or severe magnesium deficiency can lead to hypocalcemia. However, according to a 3-week study in which magnesium was artificially eliminated from the diet, it was found that even a small decrease in the amount of magnesium consumed can lead to a significant decrease in serum calcium concentration.
  • Oxalic acid may interfere with calcium absorption. Oxalic acid foods include spinach, sweet potatoes, rhubarb, and beans.
  • Phosphorus. Excessive phosphorus intake can interfere with calcium absorption. However, if the amount of calcium consumed is sufficient, then the likelihood of this decreases. Phosphorus is found primarily in dairy products, cola and other soft drinks, and meat.
  • Phytic acid. May interfere with calcium absorption. Found in unleavened bread, raw beans, nuts, grains, and soy products.
  • Protein. It is believed that dietary protein can lead to increased excretion of calcium in the urine. This issue is still being researched by scientists.
  • Sodium. Moderate and high intake of sodium chloride (salt) leads to an increase in the amount of calcium excreted from the body in the urine. There was indirect evidence that salt can negatively affect bones. Until this time, the recommended dosage of calcium intake depending on the salt intake has not been published.
  • Zinc. Calcium and zinc are absorbed in the same part of the intestine, therefore they can mutually influence the metabolic process. Large doses of zinc consumed can interfere with calcium absorption. Particular attention should be paid to this in elderly women, in whom the level of calcium in the body is low by itself, and with additional intake of zinc supplements, it can decrease even more.
  • Iron. Calcium can impair the absorption of iron in the body[3].

Interaction with medicines

Certain medications can interfere with calcium metabolism, primarily by increasing urinary calcium levels and thus leading to calcium deficiency. It is widely known, for example, the effect of glucocortisoids on the occurrence of osteoporosis and bone loss, regardless of age and gender. Corticosteroids increase the amount of calcium not only in the urine, but also in the stool, and as a result, negatively affect the level of calcium.

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Information sources
  1. Weaver C. M., Peacock M. . Advances in nutrition (Bethesda Md.), 2(3), 290-292. doi:10.3945/an.111.000463
  2. Jennifer J. Otten, Jennifer Pitzi Hellwig, and Linda D. Meyers. “Calcium”. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. 2006. 286-95.
  3. Kipple, Kenneth F, and Orneals, Kriemhild Conee. “Calcium”. The Cambridge World History of Food. Cambridge: Cambridge UP, 2012. 785-97. The Cambridge World History of Food.
  4. Nutri-Facts Source
  5. Cashman, K. (2002). Calcium intake, calcium bioavailability and bone health. British Journal of Nutrition, 87 (S2), S169-S177. doi:10.1079/BJN/2002534
  6. 7 Super-Powerful Food Pairings, source
  7. Diet and Nutritional Tips for Women,
  8. S. J. Fairweather-Tait, S. Southon. Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003.
  9. M. R. Clarkson, C. N. Magee, B. M. Brenner. Pocket Companion to Brenner and Rector’s The Kidney. 2nd Edition, 2011.
  10. Kimura M., Itokawa Y. Cooking losses of minerals in foods and its nutritional significance. Journal of Nutritional Science Vitaminol. 1990; 36. Supplement 1: S25-32; discussion S33.
  11. National Institutes of Health. Office of Dietary Supplements. Calcium. Factsheet for Health Professionals.
  12. Uzhegov, G. Traditional medicine: The most complete encyclopedia. 2007 year.
  13. Alanna K. Tisdale, Elvira Agrón, Sarah B. Sunshine, Traci E. Clemons, Frederick L. Ferris, Emily Y. Chew. Association of Dietary and Supplementary Calcium Intake With Age-Related Macular Degeneration. JAMA Ophthalmology, 2019;
  14. Intermountain Medical Center. “Calcium in arteries is shown to increase patients’ imminent risk of a heart attack.” ScienceDaily. 16 March 2019.
  15. Janin Lautenschläger, Amberley D. Stephens, Giuliana Fusco, Florian Ströhl, Nathan Curry, Maria Zacharopoulou, Claire H. Michel, Romain Laine, Nadezhda Nespovitaya, Marcus Fantham, Dorothea Pinotsi, Wagner Zago, Paul Fraser, Anurag Tandon, Peter St George-Hyslop, Eric Rees, Jonathan J. Phillips, Alfonso De Simone, Clemens F. Kaminski, Gabriele S. Kaminski Schierle. C-terminal calcium binding of α-synuclein modulates synaptic vesicle interaction. Nature Communications, 2018; 9 (1)
  16. Calcium Skincare Product Benefits – Repairs Aging Skin – L’Oréal Paris,
  17. Calcium Oxide, source
  18. Dietary Supplements for Weight Loss. Fact Sheet for Health Professionals,
  19. Facts About Calcium, source
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