Interesting fact about calcium


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Facts about calcium

Don’t wait till it’s too late to regret

As the population ages, there is an increasing occurrence of osteoporosis in Hong Kong. Many people think that only middle-aged and older adults need high calcium intake. In fact, adequate calcium intake is also important during childhood and adolescence to strengthen bones and reduce the risk of osteoporosis in the future.

Essential facts

There are several types of mineral in human body in which calcium is of the highest content. 99% of calcium is stored in bones and teeth, while the remaining 1% is stored in blood to help blood coagulation and muscle contraction.
When the calcium level in blood is low, calcium is released from bones to maintain blood calcium level. If calcium is continually released, there will be an excessive loss of calcium and a decrease in bone density, making the bones become weak and fragile. Therefore, calcium intake is vital to prevent osteoporosis.

Where can we obtain calcium?

  • Milk and dairy products like cheese and yoghurt are rich in calcium.
  • The calcium content of whole milk is similar to that of skimmed milk, but the fat content of whole milk is relatively higher. It is suggested that those who want to keep fit should choose low-fat or skimmed milk.

Calcium content of 1 cup (240ml) of whole milk and skimmed milk.

240ml milk Calcium (mg)
Whole milk 276
Skimmed milk 299
  • Calcium content of green leafy vegetables, fish with bones, firm tofu, calcium-fortified soy milk and nuts is high too.

Foods rich in calcium

Food group


Calcium (mg)

Dairy products

Skimmed milk 1 glass (240ml) 299
Low-fat yoghurt 1 glass (245g) 350
Low-fat cheese (Cheddar) 1 slice (28g) 118


Bok choy (cooked) 1 bowl (170g) 158
Broccoli (cooked) 1 bowl (156g) 62
Chinese kale (cooked) 1 bowl (88g) 88


Canned sardines in tomato sauce (with bones) 100g 240
Canned salmon (with bones) 100g 249

Beans/bean products

Soya bean (cooked) 1 bowl (172g) 175
Black-eye bean (cooked) 1 bowl (165g) 211
Firm tofu 100g 320
Soy milk 1 cup (240ml) 61


Almond (roasted) 100g 266
Sesame (roasted) 100g 989
Pistachio (roasted) 100g 110
Peanut (roasted) 100g 54
Cashew nut (roasted) 100g 45

Remarks: 1 bowl (1 medium-sized bowl) = 250-300ml

Reference: Centre for Food Safety, Nutrient Information Inquiry System

Daily calcium requirement

The suggested daily calcium requirement is as follows:

Age Daily requirement (mg)
4-6 800
7-10 1000
11-13 1200
14-17 1000
18-49 800

Reference: The Chinese Dietary Reference intakes (2013)

Tips for building strong bones

In order to strengthen the bones, a healthy lifestyle should be adopted since childhood.

1. Eat a balanced diet with sufficient calcium and vitamin D intake

Vitamin D helps calcium absorption. Vitamin D-rich food includes egg yolk, salmon and vitamin D-fortified milk.

2. Reduce calcium loss

3. Do regular exercise

Do more weight-bearing exercise (e.g. walking, jogging, stair climbing, tennis and dancing, etc.).
Skin produces vitamin D which helps calcium absorption when doing exercise under sunlight.

4. Avoid smoking and alcohol consumption

Concepts about calcium

Q: I do not like dairy products. Can I take calcium supplement as an alternatives?
A: Both dairy products and calcium supplements provide calcium. However, dairy products contain vitamin D, proteins, carbohydrates and other minerals in addition to calcium. According to “The Chinese Dietary Reference intakes”, daily calcium intake for those who aged 7-18 should not exceed 2000mg per day. Excessive calcium intake may lead to the formation of kidney stones and hinder iron and zinc absorption. In special circumstances, calcium supplements can be taken if they are advised by a doctor.
Q: Do children need to prevent osteoporosis?
A: People of all ages need to prevent themselves from developing osteoporosis. Bone development occurs during childhood and adolescence. The higher the density of the bones formed, the lower the risk of developing osteoporosis.

Once osteoporosis is diagnosed, is calcium absorption no more important?

A: No matter you have osteoporosis or not, calcium absorption is important because it prevents osteoporosis flare-up and bone fracture.

Can pork bones soup and fish soup supplement calcium?


Calcium in pork bones and fish bones cannot dissolve in water easily. Therefore, the calcium content of pork bone soup and fish soup are actually very low.

Q: Can adequate daily calcium intake and regular exercise completely prevent us from bone fracture?
A: Many complications of osteoporosis like bone fractures are related to accidents and injuries. Therefore, home safety and accident prevention are also important to avoid falls and slips.
Q: Does osteoporosis occur only in the elderly?
A: Osteoporosis is not a condition that occurs only in the elderly. Actually, both male and female adults also have the risk of developing osteoporosis.


Having adequate calcium intake since childhood can help build healthy bones and prevent osteoporosis effectively.

Calcium in Nutrition and Health

Calcium – the bone mineral

Calcium is a divalent cation with an atomic weight of 40. In the elementary composition of the human body, it ranks fifth after oxygen, carbon, hydrogen, and nitrogen, and it makes up approximately 2% of total body weight (Peacock, 2010). Our bodies contain around 1200 g of calcium. Only 1% of this calcium is in the body fluids (the extracellular fluid, the blood, and the cellular fluid), the rest (99%) is incorporated in bones and teeth (Beto, 2015).

Dietary reference intakes for adequacy

Table 1: Calcium Dietary Reference Intakes (DRIs) for Adequacy (amount/day) (Institute of Medicine, 2011)

Life stage group Calcium (mg/d) Life stage group Calcium (mg/d)



1-3 years

700 9-18 years 1 300

4-8 years

1 000 19-50 years 1 000


>50 years 1 200
9-18 years 1 300

Pregnancy and Lactation

19-70 years 1 000 <19 years

1 300

>70 years 1 200 19-50 years

1 000

Calcium requirements for infants (0-12 months) are presumed to be met by human milk.

Dietary sources of calcium

Good sources of calcium include milk and other dairy products, kale, kelp, tofu, canned fish with bones, peanuts, walnuts, sunflower seeds, broccoli, cauliflower and soybeans. Fortified foods such as fruit juices, breads and cereals are also common sources of calcium in some countries. Calcium in hard water and some mineral waters may be important dietary sources for some people. Calcium supplementation is another alternative.

Table 1: Calcium content of some food sources (Wolmarans, et al., 2010).

Absorption and bioavailability of calcium from the diet

Foods and diets are far more than the sum of their single nutrients. Single nutrients are not consumed in isolation – many factors within a food influence the effects of a single nutrient and it is inaccurate to generalize about the effects of a single nutrient without considering the food it is present in. Calcium must be in a soluble form, generally ionized (Ca2+), at least in the upper small intestine or bound to a soluble organic molecule before it can cross the wall of the intestine (Guéguen & Pointillart, 2000).

Absorption is taking place from the first and second part of duodenum against concentration gradients. When calcium intake is adequate, differences in bioavailability, as from increased solubilisation, play no or only a minor role in the amount of calcium that is absorbed or deposited in the skeleton. When, however, the dietary calcium intake is low and in the form of poorly soluble or poorly digestible sources (e.g., some green leafy vegetables), the decrease in calcium absorption compared to a source like milk becomes nutritionally significant (Bronner & Pansu, 1999).

The absorbability of calcium affects calcium utilisation by the body. Several molecules in the diet solubilise calcium or keep it in solution within the ileum, in particular phosphor-peptides derived from casein and amino acids like L-lysine and L-arginine, which form soluble chelates with calcium (Scholz-Arens & Schrezenmeir, 2000). Lactose, lactic acid and other carbohydrates, which are more gradually absorbed, also have an effect, but the mechanism involved is still a matter of controversy. It is now generally agreed that lactose, at least in high doses (15% – 30%), increases the passive absorption of calcium (Guéguen & Pointillart, 2000; Kwak, et al., 2012). Bacterial fermentation may also enhance calcium absorption in fermented milk (Pretorius & Schönfeldt, 2013).

On the other hand, organic acids such as oxalate (found in green leafy vegetables) and phytates (found in grain products) forms insoluble complexes with calcium at near-neutral pH values and may decrease calcium absorption (Kärkkäinen, et al., 1997; Heaney, et al., 1988). Calcium found in vegetables or other non-fluid foods cannot go into solution until at least some part of the food has been digested. Calcium must be dissociated from its ligands in a foodstuff prior to absorption. Therefore foods with high fibre content are likely to be poorer sources of calcium than foods that contain less or no fibre but an equivalent amount of calcium (Bronner & Pansu, 1999).

From a nutrition standpoint, both calcium content and bioavailability are important. Bioavailability is simply the proportion of an ingested nutrient that is available for metabolic processes and storage (Schönfeldt, et al., 2016). Bioavailability is a major issue with dietary calcium, as it can vary significantly in different dietary sources. Intestinal calcium absorption from dairy products has been estimated to range between 32% and 35%, but from spinach (rich in oxalates) it was a mere 5% (Weaver, et al., 1999). In practical terms this suggests that although the label indicates the foods or beverages have the same calcium per serving, in fact the bioavailability, or the amount of calcium the body absorbs and uses from the food will be different. Dairy is not the only food with a high calcium bioavailability. Calcium in cabbage, bok choy (type of Chinese cabbage) and broccoli is also highly bioavailable. However, because their total calcium content is lower than in dairy, you would need to eat a lot more servings to reach the DRI for calcium.

It is important to always remember that it is difficult to discuss calcium alone. Calcium metabolism is a collaborative process between involving other nutrients, such as phosphorus, vitamin D and protein.

Calcium to Phosphorus ratio

In human milk the ratio of calcium to phosphorus is as much as 2:1 or slightly higher. In cow’s milk the ratio is typically 1:0.8. It has been suggested that the extra phosphate somehow “leaches calcium out of the bones” into the urine, but this has not been proven. Phosphorus does inhibit calcium absorption to a small degree, but it also reduces calcium excretion. Adequate intakes of calcium and phosphorus are required for normal bone mineralisation (Heaney, 2009; Peacock, 2010). There are indications that excess phosphorus in the diet (eg. high consumption of soda drinks) may adversely affect bone health, but it must be remembered that this is in the context of the overall diet, and that merely comparing ratios in individual foods cannot predict the effects in the body when other foods are also consumed. It is reported that a Ca:P molar ratio higher than 0·50 is sufficient when dietary Ca intake is at the recommended level (Kemi, et al., 2010).

Lactose intolerance

The lactose concentration in bovine milk is about 5 g / 100 ml (Wolmarans, et al., 2010). People often confuse a milk allergy with lactose intolerance, but they are not the same thing. Lactose intolerance is common in many adults throughout the world, and is caused by deficiency of intestinal lactase. Avoiding all lactose is seldom necessary, and persons with lactose intolerance can usually ingest limited amounts of milk without having negative symptoms. To ingest milk with a meal may also improve tolerance. Instead of drinking regular milk, fermented milk, yoghurt and cheese may be an alternative option, as fermented dairy products contains less lactose than fresh milk, and it also may contain bacterial lactase that may be activated when the fermented milk reaches the gut (Haug, et al., 2007).

Nutritional Habits

Bone formation and maintenance is a lifelong process. Early attention to strong bones in childhood and adulthood will provide more stable bone mass during the aging years.

Both adolescents and elderly populations often have high risk of calcium deficiency due to dietary habits. Adolescents throughout the world are growing in risk due to dietary pattern changes. Many adolescents decrease calcium intake by substituting milk with soda drinks or due to eating disorders. The elderly are at risk for multiple reasons including low calcium intake over time, medication interactions that may decrease dietary calcium absorption, and osteoporosis that changes bone formation and strength (Beto, 2015).

Consumption of adequate dietary calcium can be accomplished within a variety of tastes and lifestyle choices. For most individuals, liberal consumption of dairy products is the easiest approach and is the least restrictive. On the other hand, those who choose to meet their calcium needs completely from plant sources need to be aware of not only the calcium content of plants but also the bioavailability of the calcium because other plant constituents can inhibit calcium absorption.


Beto, J. A., 2015. The role of calcium in human aging. Clinical Nutrition Research, 4(1), pp. 1-8.

Bronner, F. & Pansu, D., 1999. Nutritional aspects of calcium absorption. Journal of Nutrition, Volume 129, pp. 9-12.

Haug, A., Høstmark, A. T. & Harstad, O. M., 2007. Bovine milk in human nutrition – a review. Lipids in Health and Disease, 6(25).

Heaney, R. P., 2009. Dairy and bone Health. Journal of the American Collegae of Nutrition, 28(1), pp. 82S-90S.

Institute of Medicine, 2011. Dietary reference intakes for calcium and vitamin D. Washinton, DC: The National Akademies Press.

Kemi, V. E. et al., 2010. Low calcium:phosphorus ratio in habitual diets affects serum parathyroid hormone concentration and calcium metabolism in healthy women with adequate calcium intake. British Journal of Nutrition, Volume 103, pp. 561-568.

Peacock, M., 2010. Caliucm metabolism in health and disease. Clinical Journal of the American Society of Nephrology, Volume 5, pp. S23-S30.

Pretorius, B. & Schönfeldt, H. C., 2013. Metabolic effect of milk and fermented milk on parathyroid hormone response and bone metabolism. Cape Town, Proceedings of the Nutrition and Health conference IDF World Dairy Summit 2012.

Scholz-Arens, K. E. & Schrezenmeir, J., 2000. Effects of bioactive substances in milk on mineral and trace element metabolism with special reference to casein phosphopeptides. British Journal of Nutrition, 84(Supplement 1), pp. S147-S153.

Wolmarans, P. et al., 2010. Condensed Food Composition Tables for South Africa. Cape Town: Medical Research Council.

Updated for FACS by BPr (2018).

The FACS objective is to provide consumers with scientifically correct information on food and nutrition issues. Articles are written by trained technical food and nutrition professionals who source information from respectable scientific sources throughout the world. The Service is administered by SAAFoST – a non-profit organisation for food scientists and other technical food professionals. Information from FACS articles, identified as such in the article index, can be freely used on condition that the source is acknowledged. See for further details and articles or call SANCU on weekdays between 08:30 and 12:00 for more information: Tel: +-27-12- 428 7122 / fax: +27 (0) 86 672 8585

5 Key Facts About Calcium

Calcium is one of the essential nutrients, vital for many bodily functions and for strong bones and teeth. “Calcium is really a very important,” says Katherine Tallmadge, RD, a spokesperson for the American Dietetic Association. “Without it, we would die, which is the definition of an essential nutrient.” Calcium is found in certain foods as well as being available in dietary supplements — such as calcium supplements and calcium magnesium supplements, which supply both essential minerals. Here are some basic facts you need to know about calcium.

Q. What is calcium?

A. Calcium is a mineral. Our bodies contain more calcium than any other mineral. As much as 99 percent of the calcium in our bodies is stored in our teeth and bones, although it is also present in our blood, muscle, and the fluid between body cells.

Q. What does calcium do?

A. Calcium is essential for building and maintaining our bones. We have to have enough calcium at all times to ensure that our bones have adequate structure, says Tallmadge. Calcium is also necessary for the contraction and expansion of muscles and blood vessels, the secretion of hormones and enzymes, and nerve impulse transmission throughout the nervous system. “We need a constant amount of calcium,” Tallmadge says. “Not getting enough calcium increases your risk of osteoporosis, hypertension, colon cancer, and preeclampsia.”

Q. How much calcium do I need?

A. Your daily calcium requirement depends on your age and a variety of other factors. For example, teens need more calcium than adults; older adults, particularly post-menopausal women, need extra calcium to prevent osteoporosis because the lower levels of estrogen that accompany menopause decrease bone mass, says Tallmadge. People with conditions such as Crohn’s or celiac disease, which can interfere with calcium absorption, may need extra calcium. And because dairy is a major source of calcium, those who do not or cannot eat dairy may require calcium supplements, says Tallmadge. Here is an overview of how much calcium we need at different stages of life:


  • 0 to 6 months: 200 milligrams (mg) per day
  • 7 months to 1 year: 260 mg
  • 1 to 3 years: 700 mg
  • 4 to 8 years: 1,000 mg
  • 9 to 18 years: 1,300 mg


  • Women 19 to 50 years and men 19 to 70 years: 1,000 mg
  • Women 51 years and older and men 71 years and older: 1,200 mg
  • Pregnant and breastfeeding women under age 19: 1,300 mg
  • Pregnant and breastfeeding women over age 19: 1,000 mg

It’s important to know that calcium by itself is not enough. “You need a balanced diet including adequate protein and vitamin D levels in order to absorb calcium into your bones,” says Tallmadge.

Q. How can I get the calcium I need?

A. The best way to get calcium is by eating foods that contain high amounts of the mineral. Many foods such as dairy products contain high amounts of calcium. Calcium is also often added to foods such as juices. Top calcium-rich choices include:

  • Dairy products such as cheese, milk, and yogurt
  • Green, leafy vegetables such as spinach and kale
  • Foods fortified with calcium such as juices, tofu, cereals, rice milk, and soymilk

Milk is a particularly good source of calcium because it is usually fortified with vitamin D. So are some other dairy products — always read product nutrition labels to be sure, and choose low- or no-fat dairy foods for better health. Certain fish, such as salmon, also supply vitamin D.

If you need more calcium than you’re getting through food, your doctor might recommend a dietary supplement. Calcium citrate can be absorbed well on an empty or full stomach, while calcium carbonate is best absorbed when taken with a meal.

Q. What are the findings of recent research studies of calcium?

A. Previous research has suggested that people who do not get adequate amounts of calcium may be at increased risk of high blood pressure, and that people who take more calcium may have a reduced risk of weight gain, stroke, and colon cancer. However, the evidence for this is not conclusive.

Recently, researchers at Brigham and Women’s Hospital in Boston reviewed 17 previous studies on the effects of calcium and vitamin D. They found that while some studies suggested vitamin D may reduce the risk of cardiovascular disease, this was not true of calcium. A recent Swedish study of more than 23,000 men over a nine-year period showed that taking extra calcium did seem to lower the risk of certain chronic diseases.

While there is some evidence suggesting that calcium may be associated with health benefits and reduced risk of some chronic diseases, researchers say more studies are needed to determine exactly what role calcium might play.

Calcium: A Quick Guide to this Nutrient of Concern

If there’s one mineral Americans know a lot about, it’s calcium. Thanks to the long-running “Got Milk?” campaign, we know calcium is important for strong bones and that milk contains plenty of it. So why are Americans falling short on this important nutrient? Learn everything you need to know about calcium and the new FDA regulations that affect calcium labeling.

Calcium Declared a Nutrient of Public Health Concern

The Dietary Guidelines for Americans 2015-2020 have identified calcium as one of the five nutrients of public health concern for Americans. The others are potassium, vitamin D, dietary fiber, and for women of childbearing age, iron.1 A nutrient of public health concern is one that is under-consumed by the population and has health risks associated with its underconsumption.

Nutrition Label Changes for Calcium

The new nutrition label regulations require all the nutrients of public health concern to be listed on the nutrition panel. Calcium, iron, and dietary fiber remain mandatory label nutrients as before. However, new to the lineup are potassium and vitamin D, which are replacing vitamins A and C. While vitamins A and C are no longer mandatory, they can still be included on the nutrition label as voluntary label nutrients.

In addition, the vitamins and minerals listed on the nutrition label must be declared in terms of weight (e.g., mg for calcium), as well as % DV. Another change affecting calcium is a DV update from 1000 mg to 1300 mg, an increase of 30%.

When manufacturers update their nutrition labels, the % DV of calcium must be recalculated based on the new DV. The increase in DV for calcium means that in order to maintain a product’s current % DV declaration, it will most likely be necessary to add more calcium to the product. Product developers should be especially alert to any changes in a product’s taste, mouthfeel, appearance, and pH when they test increased calcium levels in a product.

Why We Need Calcium

Calcium is the most abundant mineral in the body. While calcium is stored primarily in the teeth and bones, a small percentage of the body’s calcium is present in the blood, muscle cells, and nerve cells. The main functions of calcium in the body include:

  • Development and maintenance of teeth and bones
  • Constriction and relaxation of blood vessels
  • Muscle contraction
  • Nerve signaling
  • Secretion of hormones (such as insulin)
  • Blood clotting

Adequate calcium intake is vitally important for maintaining healthy and strong bones over time. When calcium intake is not sufficient to cover the essential functions requiring calcium, calcium is released from the bones to compensate, drawing down the body’s reserves. Insufficient calcium levels are associated with softened or brittle bones, fractures, and osteoporosis.

How Much Calcium Do We Really Need?

To understand how much calcium is recommended, it’s important not to confuse the DV with the Recommended Dietary Allowances (RDAs). The DV for calcium, which is now 1300 mg, is a single value that serves as a reference for nutrition labels. The purpose of the DV (by way of the % DV on nutrition labels) is to allow consumers to see how their food choices contribute to their daily nutrient intake, as well as to compare the nutrient contents of different products.

RDAs, however, account for certain factors (i.e., age, sex, pregnancy, and breastfeeding) that allow for more customized nutrient recommendations. As a result, there are usually several different RDAs for one nutrient. The body’s calcium requirement increases throughout childhood, peaks in adolescence, and then declines slightly. Later on, the body’s calcium needs increase again. For calcium, the DV was set to match the highest RDA level, which is the RDA for males and females ages 9 to 18 years.

An RDA is defined as the average daily level of intake needed to meet the requirements of nearly all (97-98%) healthy individuals. When there is not sufficient scientific data to determine an RDA for a nutrient, the Adequate Intake (AI) is used instead. This is the case for calcium for ages 0 to 12 months. The AI for calcium in this age range is based on the average calcium content of breast milk for an assumed intake volume.

Recommended Iron Intakes for Different Groups.

Food Sources of Calcium

While calcium is strongly associated with dairy products (which contain very high levels), dairy is not the only source of calcium. Large amounts of calcium can be found in the following types of foods:

  • Dairy products – especially milk, yogurt, and cheese
  • Dark leafy greens – such as kale, turnip greens, and bok choy
  • Seeds – especially chia, sesame, and poppy seeds
  • Fish with edible bones – such as canned sardines and salmon
  • Certain legumes – such as white beans and edamame
  • Calcium-fortified foods and beverages – such as tofu, soy milk, orange juice, and breakfast cereal

Almonds, amaranth, dried figs, and blackstrap molasses also contribute some calcium. In addition, there is a small amount of calcium naturally present in grains. This calcium contribution becomes notable due to the high consumption of grain-based products (especially bread) that’s characteristic of the American diet.

The Important Role of Vitamin D

A variety of factors are known to impact calcium absorption. One of the most significant of these is vitamin D. Vitamin D, which can be synthesized by the skin during exposure to sunlight or consumed through the diet, is known to improve calcium absorption.

Insufficient vitamin D carries with it the same health risks as insufficient calcium. Unfortunately, vitamin D is another nutrient of public health concern, meaning many Americans are not consuming enough. Dietary intake of vitamin D is particularly important for those living in northern latitudes (where intense sunlight is scarce in the winter) and for those who spend little time outdoors.

For products that contain calcium, either naturally or through fortification, manufacturers should pay close attention to the vitamin D content. As consumers become increasingly aware of the relationship between calcium and vitamin D, they will likely expect their calcium-containing foods and beverages to contain vitamin D (as is common in dietary supplements). The new mandatory nutrition labeling of vitamin D will put a spotlight on this important nutrient.

Making the Future of Food Even Better

Though healthy eating may be trending, we still have a lot left to do—as manufacturers and consumers—before we’re all eating healthy. Formulating with careful attention to the nutrients of public health concern (which are also mandatory label nutrients) will go a long way toward improving the health of a public that loves packaged foods.

If you’re interested in learning more, please

20 Ca 40.08

The chemical element calcium is classed as an alkali earth metal. It was discovered in 1808 by Sir Humphry Davy.

Data Zone

Classification: Calcium is an alkali earth metal
Color: silvery-gray
Atomic weight: 40.078
State: solid
Melting point: 842 oC, 1115 K
Boiling point: 1484 oC , 1771 K
Electrons: 20
Protons: 20
Neutrons in most abundant isotope: 20
Electron shells: 2,8,8,2
Electron configuration: 1s2 2s2 2p6 3s2 3p6 4s2
Density @ 20oC: 1.55 g/cm3

Show more, including: Heats, Energies, Oxidation, Reactions,
Compounds, Radii, Conductivities

Atomic volume: 29.9 cm3/mol
Structure: ccp: cubic close packed
Hardness: 1.75 mohs
Specific heat capacity 0.63 J g-1 K-1
Heat of fusion 8.54 kJ mol-1
Heat of atomization 178 kJ mol-1
Heat of vaporization 153.6 kJ mol-1
1st ionization energy 589.8 kJ mol-1
2nd ionization energy 1145.4 kJ mol-1
3rd ionization energy 4911.8 kJ mol-1
Electron affinity 2 kJ mol-1
Minimum oxidation number 0
Min. common oxidation no. 0
Maximum oxidation number 2
Max. common oxidation no. 2
Electronegativity (Pauling Scale) 1
Polarizability volume 22.8 Å3
Reaction with air vigorous, ⇒ CaO, Ca3N2
Reaction with 15 M HNO3 vigorous, ⇒ H2, Ca(NO3)2
Reaction with 6 M HCl vigorous, ⇒ H2, CaCl2
Reaction with 6 M NaOH none
Oxide(s) CaO
Hydride(s) CaH2
Chloride(s) CaCl2
Atomic radius 180 pm
Ionic radius (1+ ion)
Ionic radius (2+ ion) 114 pm
Ionic radius (3+ ion)
Ionic radius (1- ion)
Ionic radius (2- ion)
Ionic radius (3- ion)
Thermal conductivity 201 W m-1 K-1
Electrical conductivity 31.3 x 106 S m-1
Freezing/Melting point: 842 oC, 1115 K

Calcium metal stored under an argon atmosphere. Image by Matthias Zepper

Rome’s Colosseum, resisting the ravages of time (okay, there are one or two missing pieces…) with the aid of calcium oxide based cement. Photo: David Iliff.

Stalactites – Mainly Calcium Carbonate.

Discovery of Calcium

Dr. Doug Stewart

People have used calcium’s compounds for thousands of years – in cement, for example.

Limestone was called calx by the Romans. The Romans heated calx, driving off carbon dioxide to leave calcium oxide. To make cement, all you have to do is mix calcium oxide with water. The Romans built vast amphitheaters and aqueducts using calcium oxide cement to bond stones together. (1)

Despite the long history of calcium’s compounds, the element itself was not discovered until electricity was available for use in experiments.

Calcium was first isolated by Sir Humphry Davy in 1808 in London. In a lecture to the Royal Society in June 1808, Davy described his experiments that year, which produced tiny amounts of metal, at best. He could not find any way to produce more calcium metal until a letter from Jöns Berzelius in Stockholm pointed him in the right direction. (3)

Davy learned that Berzelius and Magnus Pontin had used a battery to decompose calcium oxide at a mercury electrode and they had obtained an amalgam of mercury and calcium. (Berzelius, the great Swedish chemist, exchanged a great deal of information with Davy. Berzelius had earlier learned from Davy that potassium could be dissolved in mercury to form an amalgam. Berzelius had extended the method.) (3),(4)

Davy made a paste of slaked lime and red oxide of mercury . (3)

He made a depression in the paste and placed about 3.5 grams of mercury metal there to act as an electrode. Platinum was used as the counter electrode. Davy carried out the experiment under naptha (a liquid hydrocarbon under which he had found he could safely store potassium and sodium).

When electricity was passed through the paste, a calcium-mercury amalgam formed at the mercury electrode.

Davy removed the mercury by distillation to reveal a new element: calcium.

Davy used the same procedure to isolate strontium, barium, and magnesium.

He named the metal calcium because of its occurrence in calx.

Interesting Facts about Calcium

  • Calcium is the most abundant of the metallic elements in the human body. The average adult body contains about 1 kg or 2 lb of calcium, 99% of which is in the bones and teeth. Only oxygen, carbon, hydrogen and nitrogen are more abundant in our bodies than calcium.
  • Calcium not only builds the structures that support our bodies, many of us also live in homes built using structural concrete or cement made with lime (calcium oxide). Snails and many shellfish use another calcium compound – calcium carbonate – to build their own homes too – their shells.
  • Modern humans were not the first people to make use of calcium to build things. Egypt’s pyramids were built using limestone blocks. Limestone is crystalline calcium carbonate. In the later pyramids, the blocks were held together with gypsum or lime based mortar. Gypsum is calcium sulfate dihydrate and lime is calcium oxide.
  • Have you ever wanted to be ‘in the limelight?’ Lime is calcium oxide, which produces a brilliant, intense light when burnt in an oxyhydrogen flame. It was used to light the stage in theaters during the 1800s until electricity took over – hence the saying.
  • Cells in animals and plants must communicate with other cells. This is called signaling. Calcium ions are the most important messengers between cells in living things and are absolutely vital for the existence of multicellular life forms.

Calcium metal burning in air to form calcium nitride and calcium oxide.

Calcium metal reacting with water, producing calcium hydroxide and hydrogen gas.

Appearance and Characteristics

Harmful effects:

Non-toxic and an essential metal for living organisms.


Calcium is reactive and, for a metal, soft. With a bit of effort, it can be cut with a sharp knife.

In contact with air, calcium develops a mixed oxide and nitride coating, which protects it from further corrosion.

Calcium reacts easily with water and acids and the metal burns brightly in air, forming mainly the nitride.

Uses of Calcium

Calcium forms alloys with aluminum, beryllium, copper, lead, and magnesium.

It is used in the manufacture of other metals such as uranium and thorium.

Calcium is used to remove oxygen, sulfur and carbon from alloys.

Calcium from limestone is a vital component of Portland cement.

Quicklime (CaO) is used in many applications in the chemical industry, such as treatment of drinking water – especially for water softening and arsenic removal, animal waste and wastewater.

Abundance and Isotopes

Abundance earth’s crust: 4.2 % by weight, 2.2 % by moles

Abundance solar system: 70 parts per million by weight, 2 parts per million by moles

Cost, pure: $20 per 100g

Cost, bulk: $ per 100g

Source: Calcium occurs in nature in various minerals including limestone (calcium carbonate), gypsum (calcium sulfate) and fluorite (calcium fluoride). Commercially it can be made by the electrolysis of molten calcium chloride, CaCl2. The pure metal can also be produced by replacing the calcium in lime (CaCO3) with aluminum in hot, low pressure retorts.

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65 Calcium Facts Every Person Should Know!

The 20th element on the Periodic Table, Calcium is one element without which the human skeleton structure cannot exist. Now, do you understand its importance? Well, since you know the importance of Calcium, we will take you through 65 fascinating Calcium facts covering its discovery, characteristics, uses, and more. So, grab your coffee, pull up your sleeves, and join us on this incredible journey of learning – a journey that never ends!

Let us begin!

Facts about Calcium – Some Basic Information at a Glance

Element Name Calcium
Element Symbol Ca
Element Family Alkali Earth Metal
Color Silvery-gray
State Solid
Atomic Weight 40.078
Melting Point 842˚C or 1115 K
Boiling Point 1484˚C or 1771 K
Density at 20˚C 1.55 g/cm3
Number of Electrons 20
Number of Protons 20
Number of Neutrons (as found in the most abundant isotope) 20
Electronic Configuration 1s2 2s2 2p6 3s2 3p6 4s2
Known Isotopes 25 know isotopes so far
Element Structure Cubic close-packed or ccp
Atomic Radius 180 pm
Hardness 1.75 mohs

Facts about Calcium – Isotopes of Calcium

Isotope Name Type and Abundance Half-Life (HL)
34Ca Radioactive < 35 nanoseconds
35Ca Radioactive 25.7 milliseconds
36Ca Radioactive 102 milliseconds
37Ca Radioactive 181.1 milliseconds
38Ca Radioactive 440 milliseconds
39Ca Radioactive 859.6 milliseconds
40Ca Radioactive and 96.94% natural abundance > 3.0×10+21 years
41Ca Radioactive 1.02×10+5 years
42Ca Stable and 0.647% natural abundance Stable, and hence, no HL
43Ca Stable and 0.135% natural abundance Stable, and hence, no HL
44Ca Stable and 2.09% natural abundance Stable, and hence, no HL
45Ca Radioactive 162.61 days
46Ca Radioactive and 0.004% natural abundance > 0.28×10+16 years
47Ca Radioactive 4.536 days
48Ca Radioactive and 0.187% natural abundance > 5.8 x 1022 years
49Ca Radioactive 8.718 minutes
50Ca Radioactive 13.9 seconds
51Ca Radioactive 10.0 seconds
52Ca Radioactive 4.6 seconds
53Ca Radioactive 90 milliseconds
54Ca Radioactive 86 milliseconds
55Ca Radioactive 22 milliseconds
56Ca Radioactive 11 milliseconds
57Ca Radioactive > 620 nanoseconds
58Ca Radioactive > 620 nanoseconds

Now that we have all the basic information in hand, we can proceed with our facts list. Shall we? Fine! Let us start.

Calcium Facts: 1-6 | Use of Calcium by Romans

1. Like many other elements on this Earth, Calcium was already in use for several thousand years. For instance, the element was used in the form of cement.

2. One of the most well-documented applications of Calcium compound was during the Roman era. The Romans used Calx.

3. Calx was nothing but Limestone. Romans used to call Limestone as Calx.

4. The Romans used to heat the Calx to remove Carbon Dioxide from it. What was left behind was Calcium Oxide.

5. They then mixed the Calcium Oxide with water to make cement. They used the cement for building massive amphitheaters as well as aqueducts.

6. The Romans used the cement for binding stones together in those structures.

Calcium Facts: 7-11 | Discovery of Calcium in Early 19th Century

7. Yes, Calcium compounds were extensively used throughout history. The only problem was that no one knew about elemental Calcium.

8. It was only after the discovery of electricity that attempts were made to isolate Calcium.

9. The first successful isolation of Calcium took place in 1808. The person who achieved it was Sir Humphry Davy. He did this in London.

10. In June 1808, Davy gave a lecture in the Royal Society. During the lecture, Davy gave a complete account of the experiment that he used for isolating Calcium.

11. The experiment that Davy used was capable of producing only tiny amounts of Calcium. Davy failed to figure out how to produce more Calcium.

Calcium Facts: 12-20 | Some Help from Jöns Berzelius

12. Davy understood what to do to produce more Calcium only after he received a letter from Jöns Berzelius.

13. In the letter, Berzelius told Davy that along with Magnus Pontin, Berzelius managed to produce an amalgam of Mercury and Calcium.

14. Pontin and Berzelius used Calcium Oxide and decomposed the compound on a Mercury electrode using a battery. This resulted in the production of the Mercury-Calcium amalgam.

15. Berzelius, who was a brilliant chemist from Sweden, was always in contact with Davy and it was Davy who told Berzelius that one could dissolve Potassium into Mercury to produce an amalgam.

16. Berzelius used the information from Davy and extended it to produce Mercury-Calcium amalgam.

17. After hearing from Berzelius, Davy took the slaked lime and red oxide of Mercury and made a paste. Slaked lime is Calcium Hydroxide formed by slightly moistening Calcium Oxide.

18. Once he made the paste, he created a depression right in the middle of it. Davy placed precisely 3.5 grams of Mercury into the depression.

19. The Mercury was placed there to act as an electrode. Davy then used Platinum as a counter electrode.

20. He carried out the entire experiment under a liquid hydrocarbon called Naphtha. Naphtha, a Davy found out earlier, was a perfect medium to store Sodium and Potassium safely.

Calcium Facts: 21-25 | Davy Isolates Calcium from Mercury-Calcium Amalgam

21. After Davy created the entire setup, he passed electricity through the slaked lime and Mercury red oxide paste.

22. The electricity did the necessary trick and created Mercury-Calcium amalgam at the Mercury electrode.

23. Once Davy received the Mercury-Calcium amalgam, he used the method of distillation to remove Mercury from the amalgam successfully. This isolated a new metal – Calcium.

24. It was Humphry Davy who gave the element the name Calcium. He derived the name from Calx – the compound that Romans used.

25. Humphry Davy later went to isolate Magnesium, Barium, and Strontium using the same method he used for separating Calcium.

Calcium Facts: 26-36 | Properties of Calcium

26. Calcium is a very ductile metal. This means that it can be drawn into a thin wire very easily.

27. Calcium has 20 electrons out of which the last two are the valence electrons in the s-orbital (the outermost shell). So, Calcium easily gives up the two valence electrons to get the stable configuration of Argon.

28. Since Calcium almost always gives up two electrons, it always forms dipositive ions and, in its compounds, it is almost always divalent.

29. Compared to Lead, Calcium is harder. However, you can still cut it using a knife if you put in some effort.

30. One of the most important properties of Calcium is that the element quickly reacts with atmospheric Oxygen. So, it cannot be used as a conductor for terrestrial applications. Thus, scientists are thinking of using it in space as a conductor.

31. In the flame test, Calcium always burns with a bright orange-red flame.

32. Calcium spontaneously reacts with water, and this reaction is faster than the reaction between Magnesium and water.

33. On the other hand, the reaction between Strontium and water is faster than the reaction between Calcium and water.

34. When Calcium is finely divided, it will burn in air spontaneously to produce nitride.

35. In the presence of moist air, Calcium will quickly form a hydration coating. It is because of this, the only way to indefinitely store Calcium at room temperature is to maintain a relative humidity of less than 30%.

36. Calcium can dissolve directly into liquid ammonia. The resulting solution is dark blue.

Calcium Facts: 37-48 | Biological Role of Calcium – Uses of Calcium in Lifeforms

37. Calcium plays a critical role in all living organisms. In particular, it is vital for the growth of healthy bones and healthy teeth.

38. The bones in the human body contain Calcium Phosphate as the main component.

39. Did you know that nearly 1 kilogram of Calcium is present in an adult human body?

40. In plant and animal cells, Calcium plays a vital role in cellular communication. Calcium ions play the role of messengers among cells. Hence, the element plays a very essential role in multicellular organisms.

41. The human body cannot absorb Calcium directly. Though we are being said that we should drink cow’s milk to get more Calcium, the truth is entirely different. The human body cannot absorb the Calcium present in milk. Read our thorough article on Milk Myth now.

42. Did you know that to absorb Calcium, the human body needs Vitamin D? But again, Vitamin D should be in its activated form known as Calcitonin.

43. To activate Vitamin D, the body needs Magnesium, which is a cofactor in 80 percent of all cellular enzymes present in our body.

44. Did you know that Calcium is the 5th most abundant element in the human body?

45. While Calcium is the 5th most abundant element in the human body, it is ‘THE MOST ABUNDANT’ metal in the human body!

46. Of all the Calcium present in human body, 99% is stored in teeth and bones. The remain 1% does a wide range of activities in the body including assisting the movement of blood, transfer of a message between the brain and other body parts, the release of enzymes and hormones, etc.

47. Did you know that Calcium is also present in cartilages found in the human body? Cartilage is a soft connective tissue that is located in the rib cage, nose, ear, and between various joints in our body.

48. There is a specialized gland in the human body that is responsible for regulating Calcium in our body. The gland is known as the Parathyroid Gland. This gland is a part of the Endocrine System.

Calcium Facts: 49-59 | Calcium Fun Facts

49. Calcium is the 5th most abundant element (by mass) in Earth’s crust.

50. In seawater, Calcium is the 5th most abundant dissolved ion.

51. Calcium plays a very vital role in the formation of corals.

52. Most of the Calcium salts that we know of are readily soluble in water.

53. Not only do humans use Calcium compounds for building homes, but there are also animals as well that use Calcium compounds for building their homes. For instance, many shellfish and snails use Calcium Carbonate to build their own homes that are nothing other than their shells.

54. Calcium Bicarbonate is found dissolved in Hard Water. When Hard Water reaches caves after filtering through the ground, the water precipitates out forming stalagmites and stalactites.

55. Egyptians built their pyramids using blocks of limestone. Limestone is nothing but crystallized Calcium Carbonate.

56. During later times, the Egyptians started using lime-based mortar or Gypsum for holding the limestone blocks together.

57. In case you didn’t know, lime is nothing other than Calcium Oxide, and Gypsum is nothing other than Calcium Sulfate Dihydrate.

58. You have heard the word ‘limelight’, right? But what exactly is that? Lime, as we said earlier, is Calcium Oxide. When you burn lime in an Oxyhydrogen flame, it gives a brilliant light that is quite intense. This light is called limelight.

59. Did you know, before electricity was discovered, the limelight was used to light up the stages in all theaters? Limelight was widely used in the 1800s.

Calcium Facts: 60-65 | Uses of Calcium and Availability

60. Many Calcium compounds are used for making paint, paper, lime, glass, cement, sugar, etc.

61. The compounds of Calcium are used for removing impurities of non-metallic nature from alloys.

62. Calcium has two valence electrons, and hence, it works as a reducing agent for preparing other metals like Thorium and Uranium.

63. As far as availability of Calcium is concerned, it makes up 4.1% of Earth’s crust by mass. Unfortunately, Calcium in its elemental form is not found in Nature.

64. Calcium is available in Nature in the form of various minerals such as:

  • Calcium Fluoride – usually known as Fluorite.
  • Calcium Sulfate or Gypsum.
  • Calcium Carbonate or Limestone.
  • Apatite or Calcium Chlorophosphate or Calcium Fluorophosphate.

65. The method of commercial preparation of Calcium includes the heating of lime with Aluminum. The process is carried out in the vacuum.

Sources: 1, 2, 3, 4, 5, 6, 7, 8, 9

Facts about Calcium

  • Calcium is an element on the Periodic Table of Elements
  • Even through, it does not look like iron or copper, calcium is actually a metal. Officially, it is considered an alkaline Earth metal.
  • Calcium is a Group 2 element in the periodic table, which are all alkaline Earth metals. Other alkaline Earth metals include beryllium, magnesium, strontium, barium and radium.
  • Calcium is a Period 4 element, meaning it has 4 electron shells.
  • Calcium was first identified as an element by the English Chemist Sir Humphry Davy in 1808. Mr. Davy was also responsible for becoming the first scientist to isolate the elements potasium, sodium, barium, strontium and magnesium.
  • Calcium has 24 isotopes, which is the most of any element.
  • Calcium is well-known because of some of the popular compounds which contain calcium carbonate. There is more calcium carbonate compound contained in the Earth than any other compound.
  • Calcium carbonate is found in limestone, dolomite, chalk, marble, coral reefs, sea shells and bones.
  • Calcium sulfate is also popular. Calcium sulfate is found in gypsum and alabaster. Gypsum is used to make plaster of Paris and drywall boards.
  • By heating limestone, calcium oxide (CoO) is formed. CaO is also known as lime. Lime has been used for thousands of years to make mortar. Mortar is used to hold rocks and bricks together.
  • Many caves are formed in limestone. When acidic water passes through cracks in the limestone, it breaks down the calcium carbonate in the rock and washes part of the limestone away over time. This makes voids in the limestone. Stalagmites and stalactites are the result of calcium carbonate dripping through the cave openings and leaving behind columns of solid material over time.
  • Stalactites and stalagmites are formed over time from calcium carbonate.

Human Body – Calcium Facts

  • Calcium is an important element for the human body. Most of the calcium in our body is held in our bones and teeth. There is also a small amount of calcium in our muscles, blood and nerves.
  • Calcium is stored in bones. Calcium helps people’s bones heal when they are broken.

  • One important function of calcium is to help blood clot when we get a cut. This is important so we stop bleeding.
  • Calcium is stored in bones and used by the body when needed.
  • Bones have the ability to heal because of the supply of calcium in them or in other bones throughout the body.
  • Calcium is constantly used by the body so the supply of calcium in the bones needs to be replaced.
  • Calcium is restored to the bones from the foods we eat.
  • Milk, cheese, fish, beans and green vegetables all contain the calcium that our bodies need.
  • Some foods like cereal and orange juice are fortified with calcium and other vitamins.

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