calcium

[gài]

metallic element

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This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Calcium is a kind of metallic element , atomic number 20, symbol Ca, in periodic table of ele ments Is located in the fourth cycle, the IIA family. Calcium is a silver white solid at room temperature, and its chemical properties are active, so it mostly exists in the form of ions or compounds in nature.

Chinese name: calcium^[2]
Foreign name: Calcium^[2]
CAS login number: 7440-70-2^[2]
EINECS login number: 231-179-5^[2]
Melting point: 842 ℃
Boiling point: 1484 ℃^[2]
Density: 1.55 g/cm³
Appearance: Silver white metal
Element symbol: Ca^[2]
Atomic weight: forty point zero seven eight

Atomic number: twenty
Cycle: Fourth cycle
family: Family IIA
Electronic layout: 1s two 2s two 2p six 3s two 3p six 4s two
Discoverer: humphry davy
Valence: +2
Content in the crust: 3%
Element Category: Metallic elements - alkaline earth
Chemical category: Active metal elements
Solubility: Insoluble in benzene and kerosene, soluble in acid and liquid ammonia
Storage mode: Stored in pure kerosene

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A brief history of research

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For a long time, chemists will calcium carbonate The calcium oxide obtained from calcination of limestone is regarded as an indivisible material. It was listed in the element table published by Lavoisier in 1789. But David ignored these and began to electrolyze calcium oxide in 1808. The method David chose at the beginning was not ideal, so he could not separate the metal calcium. By May 1808, David had obtained inspiration from the experiment in which Bezilius and Swedish Royal Doctor Pontin jointly electrolyzed the mixture of quicklime and mercury to obtain calcium. He will be wet quick lime and Mercuric oxide After mixing in a ratio of 3 to 1, place it on a platinum plate, connect it to the positive pole of the battery, and then mixture A large amount of calcium amalgam can be obtained by filling a hole in the middle with mercury, inserting a platinum wire, and connecting it with the negative electrode of the battery. After distillation of calcium amalgam, silver white metallic calcium is obtained. Since then, calcium has been identified as an element and named calcium, with the element symbol of Ca. Calcium comes from the Latin word calx for quicklime.

Metallic calcium (2 sheets)

Element release: the content of calcium in the crust is 4.15%, ranking fifth. The main calcium containing minerals are limestone CaCO three 、 dolomite CaCO three ·MgCO three 、 Gypsum CaSO four ·2H two O、 fluorite CaF two 、 apatite Ca five （PO four ） three F, etc. Eggshells, pearls, corals, shells of some animals and soil all contain calcium. Calcium chloride accounts for 0.15% in seawater.^[1]

Physical and chemical properties

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physical property

periodic table of ele ments The second main family. Silver white slightly soft metal, shiny. Insoluble in benzene, slightly soluble in alcohol, soluble in acid and liquid ammonia.

5Ca+2CO two →CaC two +4CaO

Ionization energy (kJ/mol)
M - M+ 589.7
M + - M 2+ one thousand one hundred and forty-five
M 2+ - M 3+ four thousand nine hundred and ten
M 3+ - M 4+ six thousand four hundred and seventy-four
M 4+ - M 5+ eight thousand one hundred and forty-four
M 5+ - M 6+ ten thousand four hundred and ninety-six
M 6+ - M 7+ twelve thousand three hundred and twenty
M 7+ - M 8+ fourteen thousand two hundred and seven
M 8+ - M 9+ eighteen thousand one hundred and ninety-one
M 9+ - M 10+ twenty thousand three hundred and eighty-five

Cell parameter
a = 558.84 pm
b = 558.84 pm
c = 558.84 pm
α = 90°
β = 90°
γ = 90°

Main absorption line and its main parameters
λ（nm）	f	W	F	S*	CL	R·S
four hundred and twenty-two point seven	one point four nine	zero point seven	A-A	zero point zero six	zero point zero zero five	-
four hundred and twenty-two point seven	-	zero point seven	N-A	zero point zero three	zero point zero zero five	one
two hundred and thirty-nine point nine	zero point zero three seven	zero point seven	N-A	twenty	-	one hundred and twenty
four hundred and forty-five point five	-	zero point seven	N-A	-	-	-

λ： wavelength

f： Vibrator strength

W： Monochromator spectrum Passband

N-A（ Nitrous oxide - acetylene Flame)

S *: element Characteristic concentration (1% absorption sensitivity)

CL: element detection limit

R · S: relative sensitivity between main absorption lines of the same element

F: Flame type

CAS NO	7440-70-2
EINECS	231-179-5
melting point	1115 K（842 °C，1548 °F）
density	1.55g/cm three
boiling point	1757 K（1484 °C，2703 °F）
Oxidized state	+2
Mohs hardness	one point seven five
oxide Dissociation energy （Do）	5.0 eV
element ionization energy （Ei）	6.11 eV
Atomic volume	25.9 cm three /mol
Content of elements in seawater	390 ppm
Crust Medium content	41000 ppm
The content of elements in the sun	70 ppm

isotope
Symbol	proton	neutron	Atomic weight	half life	Nucleus spin	relative abundance	Change rate of relative abundance
thirty-four Ca	twenty	fourteen	34.01412（32）#	<35 ns	0+	-	-
thirty-five Ca	twenty	fifteen	35.00494（21）#	25.7（2） ms	1/2+#	-	-
thirty-six Ca	twenty	sixteen	35.99309（4）	）102（2） ms	0+	-	-
thirty-seven Ca	twenty	seventeen	36.985870（24）	181.1（10） ms	3/2+	-	-
thirty-eight Ca	twenty	eighteen	37.976318（5）	440（8）ms	0+	-	-
thirty-nine Ca	twenty	nineteen	38.9707197（20）	859.6（14） ms	3/2+	-	-
forty Ca	twenty	twenty	39.96259098（22）	Stable (>5.9 × 10 twenty-one a）	0+	0.96941（156）	0.96933-0.96947
forty-one Ca	twenty	twenty-one	40.96227806（26）	1.02（7）×10 five a	7/2-	-	-
forty-two Ca	twenty	twenty-two	41.95861801（27）	stable	0+	0.00647（23）	0.00646-0.00648
forty-three Ca	twenty	twenty-three	42.9587666（3）	stable	7/2-	0.00135（10）	0.00135-0.00135
forty-four Ca	twenty	twenty-four	43.9554818（4）	stable	0+	0.02086（110）	0.02082-0.02092
forty-five Ca	twenty	twenty-five	44.9561866（4）	162.67（25） d	7/2-	-	-
forty-six Ca	twenty	twenty-six	45.9536926（24）	Stable (>100 × 10 fifteen a）	0+	0.00004（3）	0.00004-0.00004
forty-seven Ca	twenty	twenty-seven	46.9545460（24）	4.536（3）d	7/2-	-	-
forty-eight Ca	twenty	twenty-eight	47.952534（4）	4.3（38）×10 twenty-one a	0+	0.00187（21）	0.00186-0.00188
forty-nine Ca	twenty	twenty-nine	48.955674（4）	8.718（6） min	3/2-	-	-
fifty Ca	twenty	thirty	49.957519（10）	13.9（6） s	0+	-	-
fifty-one Ca	twenty	thirty-one	50.9615（1）	10.0（8） s	3/2-#	-	-
fifty-two Ca	twenty	thirty-two	51.96510（75）	4.6（3）s	0+	-	-
fifty-three Ca	twenty	thirty-three	52.97005（54）#	90（15）ms	3/2-#	-	-
fifty-four Ca	twenty	thirty-four	53.97435（75）#	50# ms （>300 ns）	0+	-	-
fifty-five Ca	twenty	thirty-five	54.98055（75）#	30# ms （>300 ns）	5/2-#	-	-
fifty-six Ca	twenty	thirty-six	55.98557（97）#	10# ms （>300 ns）	0+	-	-
fifty-seven Ca	twenty	thirty-seven	56.99236（107）#	5# ms	5/2-#	-	-

Remarks: 1 The data marked with # represents theoretical speculation without experimental proof, while the data enclosed in parentheses represents data uncertainty.

2. Calcium（ Atomic mass unit : 40.078 (4)) There are 24 isotope Among them, 5 isotopes are stable.

chemical property

Direct reaction with most nonmetals during heating, such as sulfur, nitrogen, carbon and hydrogen Calcium sulfide CaS、 Calcium nitride Ca three N two 、 Calcium carbide CaC two and Calcium hydride CaH two , react with carbon dioxide when heated.^[1]

The chemical property is active, and a layer of oxide or nitride film can be formed on the surface in the air, which can slow down further corrosion. It can be formed with oxidation calcium oxide , combined with nitrogen Calcium nitride Ca three N two , combined with fluorine, chlorine, bromine, iodine, etc. to produce corresponding halides, and hydrogen at 400 ℃ catalyzer Under the action, calcium hydride is generated. React with water at room temperature to generate calcium hydroxide and release hydrogen, react with hydrochloric acid, dilute sulfuric acid, etc. to generate salt and hydrogen, and react with carbon at high temperature to generate calcium carbide CaC two 。 Almost all metal oxides can be reduced when heated, and many metal chlorides can also be reduced when molten.

Compounds: The important compounds of calcium are Calcium hydride 、 calcium oxide 、 Calcium peroxide 、 calcium chloride 、 Calcium fluoride 、 Calcium carbide 、 calcium hydroxide 、 Calcium cyanamide 、 calcium carbonate 、 Calcium hypochlorite 、 calcium sulfate Etc. Calcium reacts with liquid ammonia to form Ca (NH three ） six Is a conductive solid with metallic luster; Calcium ions can form chelates [CaEDTA] two （ EDTA Is ethylenediaminetetraacetic acid), calcium ions can form complexes with compounds containing N, O coordination atoms, and crown ether 、 Cryptate ether Generate macrocyclic complexes. Calcium fluoride CaF two White crystal or powder, density 3.18g/cm three , melting point 1418 ℃, boiling point 2533.4 ℃, insoluble in water, soluble in strong inorganic acid to release hydrogen fluoride. The calcium fluoride minerals in nature are fluorite or Fluorspar , often gray, yellow, green, purple and other colors. Commonly used in industry calcium hydroxide And hydrofluoric acid Preparation of calcium fluoride by neutralization; Water absorption production Calcium magnesium phosphate fertilizer Waste gas reuse Lime milk Neutralization can also produce calcium fluoride. Calcium peroxide CaO two It is yellow white crystal, belonging to Tetragonal system , density 2.9g/cm three , heated to 275 ℃ for explosive decomposition; It is easily deliquescent, slightly soluble in water, and reacts with dilute sulfuric acid to generate hydrogen peroxide. Add calcium chloride aqueous solution hydrogen peroxide and ammonia , or calcium hydroxide ammonium chloride Dissolve in water, then add hydrogen peroxide. Both reactions are carried out at about 0 ℃, and CaO is precipitated two ·8H two O crystal, dehydrate and dry at 150~200 ℃ to obtain anhydrous Calcium peroxide 。^[1]

It reacts violently with water at room temperature to generate calcium hydroxide (lime) and hydrogen.

Ca+2H two O=Ca（OH） two +H two ↑ (displacement reaction)

Soluble in acid, it can decompose water and release hydrogen.

Electronic layout: 1s two 2s two 2p six 3s two 3p six 4s two

Relevant chemical equation of calcium:

Ca+2HCl=CaCl two +H two ↑ (displacement reaction)

N two +3Ca=Ca three N two (chemical reaction)

3C+CaO=CaC two +CO ↑ (redox reaction)

CO two +Ca（OH） two (Excess)=CaCO three ↓+H two O (metathesis reaction)

2CO two (Excess)+Ca (OH) two =Ca（HCO three ） two (chemical reaction)

SO two +Ca（OH） two =CaSO three ↓+H two O (metathesis reaction)

SO three +Ca（OH） two =CaSO four +H two O (metathesis reaction)

2HNO three +CaCO three =Ca（NO three ） two +H two O+CO two ↑ (metathesis reaction)

2Cl two +2Ca（OH） two =CaCl two +Ca（ClO） two +2H two O (redox reaction)

CaH two +2H two O=Ca（OH） two +2H two ↑ (redox reaction)

2HF+CaCl two =CaF two +2HCl (metathesis reaction)

SiO two +CaO=CaSiO three (chemical reaction)

(metathesis reaction)

(decomposition reaction)

Proton number	twenty
Neutron number	twenty
Atomic number	twenty
Nuclear charge number	twenty
Period	three
Number of families	IIA
Electron layer distribution	2-8-8-2
Electronic layer	K-L-M-N

Preparation method

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First, limestone and hydrochloric acid Reaction results calcium chloride ：

CaCO three +2HCl=CaCl two +H two O+CO two ↑

1. The dried anhydrous calcium chloride is put into the electrolytic cell by electrolysis method Oxyacetylene flame Anode in spray melting electrolyzer（ graphite ）Next to the raw material, namely, open the cooling water, put down the cathode (round steel), contact the liquid surface, and connect the current. Make the molten liquid flow to the cathode and connect the circuit. After most of the raw materials are melted, continue to add new materials until they are 2~3cm away from the tank edge and the temperature is normal. The metal calcium is deposited on the cathode. The current is 350~450A and the voltage is 20~25V. Before striking the metal calcium deposited on the cathode, the current should be reduced by 50~100A. After the metal calcium to be knocked out is put into the oil, the cathode contacts the electrolyte level again, and then increases the current by 50~100A. In order to maintain the temperature of the electrolytic cell, materials should be added successively. chlorine The anode escapes and is recycled.

(Calcium and by-product chlorine are obtained.)

2. Calcium can be obtained by electrolytic method and aluminothermic reduction method. The purity of molten salt of electrolytic calcium chloride is only 90%. The thermal reduction method uses aluminum to reduce calcium oxide at high temperature, and the product purity is high (99%). The process is also relatively simple, which is the method adopted in recent years. First, CaCO three CaO is obtained by roasting. Aluminum is preferably small particles or flakes. The molar ratio of calcium oxide to aluminum is 3:2. After the ingredients are mixed, the billet is made. The pressure of manual hydraulic press can be lower than that of magnesium silicon billet.

3. Metal calcium can be electrolytic fused calcium chloride at 780-800 ℃. Electrolyser can be Graphite crucible Anode graphite , using iron bar or graphite bar as cathode. The current density of cathode is kept at 100A/cm two 。 With the precipitation of metal calcium, the cathode gradually increases. Metal calcium is covered with a layer of molten calcium chloride solidified in the air to prevent oxidation. The purity of calcium obtained is 98%~99%, and the impurities are iron, silicon, aluminum, trace carbon and some chlorine.

application area

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Industrial field

It is used to make alloys with aluminum, copper, lead, and beryllium reducing agent Deoxidizer of alloy, oil dehydrogenation, etc.

be used as alloy Of Deoxidizer , oily Dehydrating agent Metallurgical reducing agent , iron and ferroalloy desulphurization With decarburizer and Electronics Getter in pipe, etc.

Biological field

Calcium is used as a high-temperature thermal reducing agent to produce chromium, thorium, uranium rare earth element , zirconium, and magnetic materials such as samarium cobalt alloy, hydrogen absorbing materials such as lanthanum nickel alloy and titanium nickel alloy. The addition of Ca – Si alloy into steel can prevent the formation of carbides. 0.04% calcium Lead calcium alloy With high hardness and corrosion resistance, it can be used as cable sheath and battery lead plate; Adding calcium to aluminum alloy can enhance plasticity. Calcium is also used for smelting tin bronze Deoxidizer for nickel and steel, Electronic tube And degassing agent and organic solvent in TV picture tube Dehydrating agent Oil refined desulfurizer, nitrogen removal agent for pure inert gas (such as helium), decomposition of malodorous thiophene and mercaptan 。 Calcium fluoride is used as optical glass light-guide fiber The raw material of enamel is used as flux. Calcium peroxide is a mild oxidant, which is used as a bactericide, antiseptic, bleaching agent, and also a quick drying agent for sealing mortar.

human beings:

Calcium is an essential element for biology. For human body, Ca is useful in muscles, nerves, body fluids and bones 2+ Binding proteins. Calcium is the main inorganic component of human bones and teeth, and also an essential element for nerve transmission, muscle contraction, blood coagulation, hormone release and milk secretion. Calcium accounts for about 1.4% of human body mass, and participates in the new supersedes the old , calcium must be supplemented every day; Inadequate or excessive calcium content in human body will affect growth and health.^[1]

Calcium is the most abundant inorganic salt element in human body. The total amount of calcium in healthy adults is about 1000~1300 grams, accounting for 1.5%~2.0% of body weight. Among them, 99% of calcium exists in bones and teeth in the form of bone salt, and the rest is distributed in soft tissues, Extracellular fluid The amount of calcium in is only 0.1% of the total amount of calcium. Bone is the main part of calcium deposition, so it is called "calcium reservoir". Bone calcium is mainly composed of amorphous calcium hydrogen phosphate (CaHPO four ）And crystalline hydroxyapatite (3Ca three PO four ×Ca（OH） two ）Two forms exist, and their composition and physical and chemical properties change with the physiological or pathological conditions of the human body. The new bone has more calcium hydrophosphate than the old bone, and gradually turns into hydroxyapatite in the process of bone maturation. Bone keeps dynamic balance between bone calcium and blood calcium through continuous osteogenesis and osteolysis.^[1]

Under normal circumstances, almost all of the calcium in the blood exists in the plasma under the action of various calcium regulating hormones blood calcium Relatively constant, 2.25-2.75mmol/L, slightly higher in children, often at the upper limit. Calcium exists in plasma and extracellular fluid in the following ways: (1) protein binding calcium. About 40% of the total blood calcium. (2) Diffusible bound calcium. Calcium combined with organic acids, such as calcium citrate, calcium lactate, calcium phosphate, etc., can diffuse through the biofilm, accounting for about 13%. （3） serum Free calcium. That is, ionic calcium (Ca), which is constantly exchanged with the above two kinds of calcium and in dynamic balance, and its content is related to the blood pH. PH decreases, [Ca] increases, pH increases, and ionic calcium decreases. In the normal physiological pH range, ionic calcium accounts for about 47%. Among the three kinds of blood calcium, only ionic calcium plays a direct physiological role. Hormones also regulate ionic calcium and are feedback regulated by the level of ionic calcium.

The concentration of intracellular ionic calcium is much lower than that of extracellular ionic calcium, which is the repository of intracellular ionic calcium. Calcium exists in cells in three forms: stored calcium, bound calcium and free calcium. About 80% of calcium is stored in organelles (such as mitochondrion 、 Sarcoplasmic reticulum 、 Endoplasmic reticulum The calcium in different organelles does not diffuse freely with each other. 10%~20% of calcium is distributed in the cytoplasm and combines with soluble protein and membrane surface, while free calcium only accounts for 0.1%.^[1]

Biological calcium ：

The so-called biological calcium is to use mature freshwater pearl clam shell as raw material, clean impurities, grind with grinding wheel or soak in NaOH solution to remove the black skin on the outer surface of the clam shell, add 3%~5% alcohol concentration to the dried, crushed and sucked clam shell fine powder, boil, sterilize, dry, smash and screen the fine powder particles to make them less than 200 mesh, and obtain white natural biological calcium powder. The natural biological calcium powder produced by this method contains about 45% calcium, and there are many kinds of amino acid It is non-toxic and hormone free. It can be used as a calcium additive in beverages and food and easily absorbed by the human body.

organization	Calcium content in wet tissue (mg/kg)
heart	seventy-six point one five
liver	sixty-four point one three
kidney	one hundred and forty point three zero
brain	eighty point one six
spleen	eighty-four point one seven
placenta	two hundred and forty-eight point five zero
skin	one hundred and seventy-two point three four
nerve	two hundred and forty-eight point five zero
smooth muscle	three hundred and thirty-two point six six
skeletal muscle	fifty-two point one zero
cartilage	260.52-400.80 Calcium and age

The recommended daily intake of calcium is 200mg for 0~0.5 years old, 250mg for 0.5~1 years old, 600mg for 1~4 years old, 800mg for 4~7 years old, 1000mg for 7~11 years old, 1200mg for 11~14 years old, 1000mg for 14~18 years old, 800mg for 18~50 years old and 1000mg for over 50 years old.

Calcium is produced by thyroid And parathyroid glands And maintain dynamic balance between blood calcium and bone calcium.

Calcium is the most abundant inorganic salt in human body: calcium is the most abundant inorganic salt in human body. The content of calcium in normal human body is 1200~1400g, accounting for 1.5%~2.0% of the body weight, of which 99% is in bones and teeth. In addition, 1% calcium mostly exists in soft tissue, extracellular fluid and blood in ionic state, and maintains dynamic balance with bone calcium. Calcium in the body, on the one hand, constitutes bones and teeth, on the other hand, can participate in various physiological functions and metabolic processes, affecting the activities of various organs and tissues.

Calcium and magnesium, potassium, sodium plasma maintain a certain proportion, so that nerves and muscles maintain normal response; Calcium can regulate the heart beat and keep the heart continuously and alternately contracting and relaxing; Calcium can maintain muscle contraction and nerve impulse transmission; Calcium can stimulate platelets and promote blood coagulation on wounds; In the body, there are many enzymes that need calcium activation to show their activity.

The human body is an organic organism Life activities In the process, it needs the participation of various substances, the type and quantity of these substances and the Element composition Basically the same. These elements remove carbon, hydrogen and oxygen to organic compound The rest are collectively referred to as minerals（ inorganic salt ）。 There are more than 20 kinds of inorganic salts in human body that can be measured.

Calcium in human body mainly exists in bones and teeth in the form of crystals. Minerals in people's bodies account for about 5% of their body weight, and calcium accounts for about 2% of their body weight. Most of the body's calcium is distributed in bones and teeth, accounting for 99% of the total, and the remaining 1% is distributed in blood, intercellular fluid and soft tissue.

Nutritional value: calcium enjoys the name of "life element", and women after 20 years old especially need supplementation. This is because, since the age of 20, the bone density has slowly decreased, and after the age of 30, the deceleration has gradually accelerated, thus laying the blame for osteoporosis and other bone diseases. In addition, calcium deficiency is also a major factor leading to female aging, so calcium supplementation is of great importance to women. Experts suggest that adult women should take at least 1000 mg of calcium every day. In case of pregnancy, lactation or menopause, it should be added to 1500 mg. The best sources are dairy products, beans, green vegetables, etc.

Milk calcium is a concentrated inorganic salt of whey, which is the best inorganic salt source of nutritional value and easy to digest and absorb. It is pure natural active high milk protein calcium extracted directly from milk.

Milk minerals rich in milk calcium are natural sources extracted from milk. The advantages of these ingredients not only provide balanced nutritional composition, but also promote the absorption and utilization of calcium, such as phosphorus, magnesium, lactose and protein. The scientific calcium phosphorus 2:1 in milk calcium is most conducive to the absorption and utilization of human body.

As milk is rich in lactose and protein, its absorption rate is much higher than other ordinary calcium. The absorption rate of milk calcium is as high as 62%~70% Calcium gluconate 2.5 times of Calcium lactate 1.75 times, 5.5 times of shellfish calcium. Consumption of milk calcium will not lead to bloating, edema and constipation, so milk is the best source of calcium for infants at present.

Calcium demand of human body during growth:

Fetal period: people need calcium supplement all their life. From the third month of the fetus, the demand for calcium of the fetus suddenly increases, and maternal low calcium will directly affect the height, weight, head, spine and limb development of the fetus. If the mother continues to lack calcium, leg cramps, miscarriage, dystocia, pelvic deformity, and even serious obstetric complications may occur during pregnancy, such as: Pregnancy hypertension 、 epilepsy , proteinuria, edema, etc., seriously endangering the life of the fetus and mother. To avoid the above problems, the daily intake of calcium during pregnancy is 800~1200 mg. When dietary calcium intake is insufficient, it should be supplemented in time.

Neonatal period: Neonatal period (within 28 days after birth): In this stage, there is an autogenous low calcium period of the fetus to stimulate the start of calcium homeostasis system. In this stage, a large amount of calcium nutrition needs to be taken from human milk. Due to the lack of vitamin D in human milk, if it is not replenished in time after 2 weeks of birth, there may be low calcium, convulsions, asthma and other dangerous symptoms.

Infancy: Infancy (born to 3 years old): This stage is the period of the most vigorous metabolism in one's life. The brain and body develop rapidly, and the baby teeth grow out. At this time, the amount of calcium in the body will directly affect the growth and development of the earlier stage. If calcium deficiency occurs, it may lead to delayed teething, anorexia, sweating, pillow baldness, chicken breasts, O-shaped legs, X-shaped legs, upper respiratory tract infection, indigestion, enteritis, etc., which will bring inconvenience to life and growth.

Pre school age to adolescence: pre school age, school age to adolescence (before 3-18 years old): this stage has a rapid growth rate, brain weight increases, the internal structure of the brain is fully developed, permanent teeth grow out, and the nervous system is mature. After puberty, the epiphysis gradually heals, and the growth of height begins to slow down and gradually stops. If calcium supplementation misses this stage, it will directly affect the health status of adults.

Adulthood: Adulthood (18-45 years old): The bone calcium storage in the body reaches the peak at this stage, but the pressure of work, study and life increases in this period, which will consume a large amount of calcium in the body. If calcium is not supplemented in this period, it will lead to various senile diseases

Middle and old age: Middle and old age (after 45 years old): With the growth of age, a large amount of calcium nutrition in the body is consumed, and calcium needs to be transferred from bone into the blood, resulting in a decrease in bone density and osteoporosis. Bone calcium loss in the elderly can reach 30%~50%. Long term transfer of bone calcium into the blood may lead to an increase in the amount of calcium in blood vessels, tissues and cells. Subsequently, calcium deposits in the blood vessel wall, myocardium and kidney cause numbness, neurasthenia, apathy, constipation, lethargy, sexual dysfunction, arteriosclerosis, coronary heart disease, diabetes, lithiasis, tumor and other elderly diseases. At this time, the thyroid C cells will secrete calcitonin to promote the reduction of bone calcium. In the process of reduction, the ectopic deposition of free calcium at the edge of the big bone joint - hyperosteogeny is formed, that is, hyperosteogeny is caused by calcium deficiency. These pathological and physiological changes have troubled the lives of many middle-aged and elderly people.

Botany: Purple alfalfa has the highest calcium content in plants. The optimal ratio of calcium: magnesium: phosphorus in human body is 2:1:1, but phosphorus It can be absorbed in food, and the phosphorus intake in people's daily diet has exceeded the proportion. The ratio of calcium to magnesium in children is 4:1.

Plants absorb calcium ions from salts such as calcium chloride. Calcium in plants is in ionic state, namely Ca2+. Calcium mainly exists in the old organs and tissues of leaves. It is a relatively difficult element to move. Calcium in Biomembrane Can be used as phospholipid Of Phosphate radical and protein The stability of the membrane structure can be maintained by bridging the carboxyl groups.

Cytoplasmic sol Calcium in soluble protein I.e calmodulin (also known as Calmodulin , camlmodulin, CaM) to form an active Ca · CaM complex Metabolic regulation Medium rise“ Second Messenger ”Role of.

Calcium is an element that forms the cell wall Intercellular layer It is composed of calcium pectinate. In case of calcium deficiency, cell wall Formation blocked, affected cell division Or new cell walls cannot be formed, and multinucleated cells appear. Therefore, the growth will be inhibited in case of calcium deficiency, and the young organs (root tip and stem tip) will fester and necrosis in case of severe calcium deficiency. Tomato stalk rot, lettuce top blight, celery split stem disease, spinach black heart disease, Chinese cabbage dry heart disease are all caused by calcium deficiency.

Calcium ions and potassium ions work together to regulate stomatal closure: when stomata are closed, the closing signal will stimulate calcium ions to enter the cytosol, making the membrane Depolarization , open anion channel, release Chloride ion and malic acid 。 According to this principle, the loss of anions will further depolarize and open Potassium ion channel The potassium ion passively extends to the adjacent Secondary guard cell and Epidermal cell The air hole will be closed.

Medical field

In daily life, if calcium intake is insufficient, the human body will have physiological calcium overdraft, resulting in a decline in blood calcium levels. When the blood calcium level drops to a certain level threshold It will induce the parathyroid gland to secrete parathyroid hormone. Parathyroid hormone has osteoclast effect, that is, calcium in bone is extracted back to maintain blood calcium level. In the early stage of calcium deficiency, when the degree of calcium deficiency is relatively mild, only reversible physiological abnormalities occur, such as ventricular premature beats, emotional instability, and decreased sleep quality in the heart. Continuous Hypocalcemia , especially after middle age, the human body is in negative calcium for a long time Equilibrium state The bone is the first to bear the brunt of hyperparathyroidism, which leads to osteoporosis and hyperosteogeny due to the continuous and large release of bone calcium. On the other hand, when the parathyroid gland continues to rise, parathyroid hormone can not close the calcium channel on the cell membrane because it can promote the opening of the calcium channel, as well as inhibit Calcium pump , which weakens the function of calcium pump and increases the intracellular calcium content. Persistent intracellular high calcium stimulates cells to become like wild horses out of control, which leads to excessive hyperactivity and cell energy depletion. At the same time, if the metabolic waste is not eliminated in time, it will cause self injury, leading to abnormal calcification and death of cells. Due to calcium deficiency, osteoporosis, hyperosteogeny, rickets in children, hand and foot convulsions, hypertension, kidney stones, colon cancer, senile dementia and other diseases occur.

Calcium can control heart rate and blood pressure, and also participate in muscle contraction. Without this substance, our bodies cannot move freely, which also explains why calcium deficient people want to lie in bed all day long. So if you feel tired due to calcium deficiency, you can eat some Italian cheese, yogurt or milk. These are high calcium foods. However, fatigue is only a manifestation of calcium deficiency. Insomnia, hypertension, premenstrual cramps, fear of cold, and even feeling overly nervous may also be signs of calcium deficiency, because calcium can help regulate the nervous system.

There are many daily foods available to help us replenish calcium and strengthen bones. For example, celery, rape, potherb mustard, mutton and chicken, as well as various fish and shrimp aquatic products and most of the dried fruits.

Modern medical research has proved that calcium deficiency will cause physiological obstacles to the human body, which will lead to a series of serious diseases. Here are some major diseases related to calcium deficiency:

Hypertension: calcium deficiency will cause abnormal calcium inflow, resulting in abnormal accumulation of calcium in vascular inner wall cells and smooth muscle cells, causing vasoconstriction, increased peripheral resistance of blood vessels, and abnormally elevated blood pressure. Continuous calcium inflow promotes blood vessel wall Elastic fibre And endothelial cells calcification, degeneration, and even attack marks, fractures. The peripheral resistance further increased, and the blood pressure continued to rise. Due to the damage of the inner wall of the blood vessel, the permeability of lipids increases, and blood lipids infiltrate into the damaged part of the blood vessel wall, causing cholesterol and other lipid substances to deposit on the blood vessel wall. Endothelin and some Activation factor , causing platelet And leukocytes adhere and gather on the vascular wall. The injury of vascular endothelial cells also activates the compensatory physiological response, which promotes the abnormal proliferation of vascular smooth muscle and fibroblasts and the displacement under the intima, resulting in the thickening and hardening of the arterial wall, so that the arterial wall is stacked in layers, large and small atherosclerosis Has formed. Research shows that for some patients with hypertension, increasing the amount of calcium preparations without drugs is helpful to control hypertension.

Coronary heart disease: Many studies show that calcium can also reduce the concentration of cholesterol in the blood, thus playing a role in protecting the heart. Someone observed, let cholesterol The men with high calcium content ate the food with low calcium content for 10 days (410 mg calcium per day), and their cholesterol content was checked; Then let them eat food with high calcium content (2200 mg calcium per day). Results High calcium food can reduce the total cholesterol by 6%, including low density lipoprotein by 11% High density lipoprotein The quantity remains unchanged. Experts believe that long-term severe calcium deficiency will lead to coronary heart disease.

Urinary calculi: The doctor told patients with kidney stones to limit calcium consumption because calcium is a major component of stones. However, after years of research, medical experts from Harvard University in the United States found that this may be a big mistake in human understanding. They suggest that the way to reduce the risk of kidney stones is to increase calcium intake. As you know, diet, especially vegetables, contains a lot of oxalate Generally, oxalate is synthesized with calcium in the intestine calcium oxalate along with faeces Discharge. If the calcium intake in the diet is insufficient, it will make the excess oxalate It is absorbed by the intestinal cavity and enters the blood, which is finally discharged by the kidney. If the human body is in negative calcium for a long time Equilibrium state Renal cells will inevitably suffer from abnormal calcium influx injury, decreased renal absorption function, and increased urinary calcium excretion. High calcium urine combines with oxalate in urine to form large and small calcium oxalate stones. If we do not avoid calcium, but take calcium supplementation measures, especially water soluble calcium supplements, then calcium oxalate is combined with oxalate in the gastrointestinal tract and diet to form calcium oxalate and excreted with feces. In addition, sufficient calcium supplementation can reverse the negative calcium balance, the renal absorption function is normal, urinary calcium excretion is reduced, and the possibility of stones is reduced.

Colon (rectum) cancer: high-fat diet will stimulate the secretion of bile excessively fatty acid Bile acid and bile acid are trigger agents that cause canceration of colon (rectum) cells. Some studies have proved that the serum bile acid content of patients with colorectal cancer is about one time higher than that of normal people, while the bile acid content of cancerous cells is more than three times higher than that of normal cells. If the mice were fed with high bile acid diet, the incidence of colon (rectum) cancer increased significantly. If sufficient calcium carbonate is supplemented, calcium ions will combine with fatty acids and bile acids to form insoluble fatty acid calcium and bile acid calcium, which will be excreted with feces, thus eliminating cancerous Trigger factor Can block the intestines cell canceration 。

Calcium and muscle contraction: the human body has a healthy posture and free Athletic ability , because there is skeletal muscle The excitement of. skeletal muscle Calcium plays a central role in the excitation of Muscle cell The concentration change of calcium ion can regulate the contraction and excitation of skeletal muscle. Even smooth muscle and heart muscle invisible from the outside of human body are also subject to various physiological reactions under the action of calcium ion. Calcium is like a commander, directing muscle movements inside and outside the body. During muscle contraction, when nerve fibers are stimulated, calcium ions flow into cells. At this time, the concentration of calcium ions in muscle is the basic condition for muscle contraction. Sarcoplasmic reticulum is the main store of calcium in muscle and the most highly developed calcium Transport system When skeletal muscle is stimulated, a large amount of calcium in sarcoplasmic reticulum will be released, and extracellular calcium ions will enter the cell, Cytosol The increase of calcium ion concentration in produces muscle contraction, and then under the action of calcium pump, the calcium ion in the muscle is discharged out of the cell to produce muscle relaxation. The whole process is rapid and transient. If calcium in muscle Equilibrium state If damaged, it will cause pain, twitching and functional decline of skeletal muscles, and will also cause abnormal movement of all smooth muscles and myocardium in the body, making the body lose dexterity and the balance and coordination function of controlling its own movement.

Tetany: This disease is caused by the lack of vitamin D in infants, which hinders the absorption of calcium and phosphorus in the intestinal tract. In addition, because the parathyroid gland fails to secrete more parathyroid hormone in time, the blood calcium decreases, causing increased neuromuscular excitability, general convulsion, hand foot spasm and laryngeal spasm, often accompanied by paroxysmal apnea and short-term asphyxia, resulting in ischemic hypoxic brain damage. According to medical observation, the cerebral nerve is most sensitive to ischemia and hypoxia. After 10 seconds of asphyxia, the neurological function begins to be impaired; A few minutes of asphyxia will lead to irreversible damage of blood vessels and nerves, which may affect children's intelligence, or lead to low energy and dementia. Therefore, it is very important to do a good job in the prevention of tetany. Children who are breastfed or artificially fed must be supplemented with enough calcium. In addition to calcium supplementation, we should also increase outdoor activities, sun exposure and supplement proper vitamin D to prevent tetany.

Osteoporosis: another serious consequence of negative calcium balance caused by long-term calcium deficiency in human body - osteoporosis. Many studies have shown that increasing calcium intake has an important slowing effect on bone loss, and also plays an important role in reducing the fracture rate caused by osteoporosis, especially when taking vitamin D while taking calcium. Many experts believe that calcium supplementation should begin at puberty, when bone is forming, and the effect will be better.

With the extension of average life expectancy, more and more elderly people, the harm of osteoporosis will become more and more prominent.

Osteoporosis often has no symptoms and signs in the early stage, and X-ray examination is not easy to find, so it has not been noticed for a long time. Even if the condition worsens, the main manifestations are bone pain and bone hyperplasia, which are often not recognized by doctors, and are often misdiagnosed as lumbar muscle strain or arthritis. With the aggravation of the disease, when the bone mass is lost to 30% - 50% of the peak bone mass, the bone becomes brittle, and a little carelessness can cause fracture. It is reported that the cumulative incidence of fractures among the elderly in Shanghai is as high as 16.5% in urban areas and 6.9% in rural areas. This kind of fracture is often difficult to heal, often due to a long time lying down, accompanied by bedsores or hypostatic pneumonia, and even death in serious cases.

Recipe

It is not necessary to take calcium tablets every day to supplement calcium. As long as you pay attention to healthy diet at ordinary times and the calcium content of meals is enough for people's daily needs, here are two recipes that can supplement calcium in daily diet for your reference:

Seaweed mixed with beancurd

Ingredients: 200g watery bean curd, 200g watery kelp, 100g cooked pig lean meat, 25g carrots, 40g cucumbers, 15g sesame oil, 25g cooked soybean oil, soy sauce, vinegar, salt, monosodium glutamate, garlic cloves, sesame paste, and chives.

make:

1. Cut inches of beancurd into filaments, blanch them in boiling water, remove them too cold, and drain the water.

2. After cleaning kelp, carrot and cucumber, cut them into inch long filaments, shred cooked lean meat, appropriate amount of chives and garlic cloves, and mince them.

3. Put all kinds of silk materials into the plate, sprinkle with chopped chives, add all seasonings when serving, mix well and serve immediately.

Rape, sea rice and bean curd soup

Ingredients: 750g tofu, 125g rape, 30g rice, 75g vegetable oil, 10g sesame oil, 7.5g monosodium glutamate, 8g salt, 20g water starch, 10g scallion flower.

make:

1. Cut the tofu into 1.5cm cubes, soak the dried rice with boiling water, then cut it into foam, pick and wash the rape and cut it into pieces.

2. Put the oil into the pot, heat it and put it into the onion stir frying pot, put in tofu and dried sea rice, stir fry it for a few times, then add rape, stir fry it thoroughly, add salt, thicken the sauce, and finally put in MSG and sesame oil.

Daily diet

Often neglected calcium supplementation methods:

The eggshell contains very high calcium. You can grind the eggshell into powder and then sprinkle the powder into food or put it into boiled water for eating or drinking, so as to facilitate the absorption of calcium by the human body.

Now let's look at the function and deficiency of calcium in the body.

1.99% of calcium is distributed in bones and teeth. Before the age of 20 is the growth stage of bones, when people grow up. People have two growth peaks: before the age of 1 year (children's calcium deficiency will lead to stunting and stunting, such as late teething, late toddlers, chicken breasts) and 12-14 years old (short stature, growth pain). Bone mass is still increasing after 20 years old. 35-40 years old, bone density Peak reached. After the age of 40, bone calcium gradually loses (for the elderly, it will accelerate the loss of bone calcium, resulting in shorter stature, osteoporosis and hyperosteogeny).

2.1% of calcium is distributed in blood, intercellular fluid and soft tissue. Maintaining the concentration of blood calcium plays an important role in maintaining normal life activities of the human body. The human body has a set of mechanisms to maintain the concentration of blood calcium. There are two sources of blood calcium: digestive tract Absorbed calcium and calcium in bones (bones are the great storehouse of human calcium, and when calcium intake is insufficient, the storehouse will be used for emergency) parathyroid glands It is regulated by secreting calcitonin and calcitonin.

3. Calcium deficiency will reduce the elasticity and toughness of soft tissue. The skin appears saggy and aging due to lack of elasticity; The lens of the eye is inelastic, easy to myopia and presbyopia; The blood vessel is inelastic and easy to harden.

4. Decrease nerve cell So calcium is a natural sedative. Calcium deficiency can lead to neurological migraine (10%~20% of women), irritability and insomnia. It may cause night fright, night cry and night sweat to babies. Calcium deficiency can also induce ADHD in children.

5. Strengthen the conduction function of the nervous system. For example, if your hand touches a glass of water, it is very hot, and you put it down quickly, there is a process of nervous system operation: receptor (Skin) - Afferent nerve - Central nerve - efferent nerve - effector (muscle). How are feelings and impulses transmitted to nerve cells, and how are nerve cells transmitted? There is a substance called neurotransmitter. Calcium contributes to the production and release of neurotransmitters.

6. Maintain normal excitation of muscle and nerve. For example, the increase of blood calcium can inhibit the excitability of muscles and nerves; When blood calcium is lower than 70mg/L, neuromuscular excitability increases and convulsions occur. Irritable bowel syndrome, dysmenorrhea in girls and calcium deficiency are important reasons.

7. Reduce (regulate) the permeability of cells and capillaries. Calcium deficiency can easily lead to allergy, edema, etc.

8. Promote the activity of various enzymes in the body. In case of calcium deficiency, Glandular cell The secretory effect of is weakened. Calcium is also an activator of enzymes.

9. Maintenance acid-base balance 。

10. Participate in the blood coagulation process. Blood coagulation is a complex process, one of which is: prothrombin - Active thrombin, which needs calcium to activate.

Calcium deficiency at different ages:

Children: Night terrors 、 Cry at night , fidgety night sweat 、 anorexia 、 Square cranium 、 rickets Skeletal dysplasia, low immunity and easy infection.

Teenagers: weak legs, cramps, poor sports performance, fatigue, irritability, lack of concentration, partial eating, anorexia, tooth decay, tooth dysplasia, susceptibility to colds and allergies.

Young adults: regular tiredness, fatigue, cramps, backache, colds and allergies.

Pregnant and lying in women: calf spasm, backache Arthralgia , edema Pregnancy hypertension Etc.
Middle and old age: low back pain, calf spasm, osteoporosis and hyperosteogeny, osteomalacia, various fractures, hypertension, cardiovascular and cerebrovascular diseases, diabetes, stones, tumors, etc.

Methods for judging calcium deficiency in children:

Maomao, who has been fat for six months, often cries at night in recent years, and his performance is not as lively as before. His mother brought him to the hospital for inspection, and the doctor determined that Maomao was short of calcium. Why

Due to the rapid growth of children, less outdoor activities and less exposure to the sun, it often causes insufficient absorption of calcium and leads to various calcium deficiency manifestations. Whether children lack calcium can be judged from the following aspects:

① It is often manifested as sweating, which has nothing to do with temperature. Especially, the head sweats after falling asleep, which makes the child's head constantly rub the pillow. After a long time, the pillow bald circle can be seen.

② They are irritable and not interested in the surrounding environment. Sometimes parents find that children are not as active as before.

③ Night terrors, who often wake up suddenly at night and cry incessantly.

④ The children after 1 year old showed late teething. Some children still did not teething when they were 1 and a half years old, and the front chimney door closed late, often not closed after 1 and a half years old.

⑤ The forehead is raised to form a square skull.

⑥ There are often beaded ribs because of the lack of vitamin D and the proliferation of costal cartilage. The cartilage proliferation of each rib is like beaded, forcing the lungs under normal pressure, which makes the children have poor ventilation and are prone to tracheitis and pneumonia.

When children suffer from severe calcium deficiency, their muscles and tendons all relax. If the abdominal wall muscle and intestinal wall muscle relax, it can cause air accumulation in the intestinal cavity and form an enlarged abdomen like a frog belly. If the tendon of the spine is loose, a hunchback may appear. After 1 year old, children learn to walk. If they lack calcium, their bones will soften. When standing, their body weight will bend their lower limbs. Some of them are "X" shaped legs, while others are "O" shaped legs, and they are prone to fracture.

Eat more foods with high calcium content, such as milk, yogurt cheese 、 Loach 、 Mussel , snail, shrimp, small Shrimp skin 、 Kelp , crispy fried fish Oysters , peanuts Sesame paste , tofu, pine nuts, cabbage, cauliflower Chinese cabbage 、 rape Etc.

Do more sports: exercise can make muscles pull each other, strongly stimulate bones, strengthen blood circulation and metabolism, reduce calcium loss, delay bone aging, and help the human body to absorb calcium in diet.

More exposure to the sun: UV can promote the synthesis of VD in the body and facilitate the absorption of calcium. But ultraviolet rays cannot penetrate the glass, so they cannot bask in the sun through the glass. Or use ZZ-2 ultraviolet therapeutic apparatus to irradiate the skin to promote the absorption of calcium.

Have a good breakfast: the body has the strongest ability to absorb calcium in the morning.

For vegetables with more oxalic acid, blanch to destroy oxalic acid before cooking. For example: Cabbage 、 cauliflower , spinach three-colored amaranth 、 Water spinach 、 leaf mustard 、 Sauerkraut Bamboo shoots.

According to the survey report of "Nutrition and Health of Chinese Residents" in 2002, the calcium deficiency of Chinese people is still very serious. The daily intake of calcium by residents is 391 mg, which is only equivalent to Recommended intake 41%.

Unreasonable dietary structure:

Oxalic acid and dietary fiber in vegetables will also prevent calcium absorption.

The dietary habits of Chinese residents directly lead to 90% of Chinese people's lifelong calcium starvation.

Bad eating habits:

Bad eating habits	Effect on calcium absorption
Smoking, drinking, often drinking carbonated drinks	Cause acidification of human body and calcium loss in human body; Carbonated drinks also contain phosphoric acid It can cause imbalance of calcium and phosphorus in the body and directly prevent calcium absorption.
Drink strong tea often	The theophylline in tea can prevent the body from absorbing calcium
Drink coffee regularly	Caffeine can promote the loss of calcium in the body and increase the excretion of calcium in urine
High salt intake	Make urinary calcium excretion increase and lose a lot
Poor diet (such as a large amount of oxalic acid Phytic acid food mixed with calcium rich food)	Causes calcium to form insoluble calcium salt precipitation, resulting in calcium unabsorption

Special physiological and pathological needs

Menopausal women（ estrogen The level suddenly decreases, bone calcium is dissolved, and the speed of bone detachment will be accelerated).

Diabetes can cause osteoporosis. (The insulin level in the blood of diabetic patients is very low, and insulin can stimulate Bone collagen The formation of helps bone retain calcium and rebuild).

Symptoms easily caused by calcium deficiency:

Calcium deficient population	Causing disease
children	Anorexia and partial eating; Difficult to fall asleep and wake up easily; Susceptibility to colds; Sparse hair; Mental retardation; Learning to walk, late teething or irregular teething; Paroxysmal abdominal pain and diarrhea; X or O leg; Chicken breast.
youth	Lack of concentration; Easy to fatigue; have a pain in the back; Low immunity; Cavity or tooth dysplasia.
Pregnant and lactating women	Cramp and fatigue; Arthralgia; dizzy; Anemia and prenatal hypertension syndrome; Edema and insufficient milk secretion.
aged	Senile skin itching; Heel pain, lumbar and cervical pain; Loose and falling teeth; Obvious hunchback and height reduction; Anorexia, peptic ulcer; Dreaminess, insomnia, irritability, irritability, etc.

Scientific calcium supplementation:

Calcium deficiency

For calcium supplement, first look at the calcium source, and safety is the key: from the calcium source, there are mainly chemical calcium agents obtained through synthesis, extraction and other means（ calcium carbonate 、 Calcium gluconate 、 Calcium hydrogen phosphate 、 Calcium amino acid chelate , bone calcium, etc.) and natural food calcium agents such as milk. Milk is recognized as the best natural food calcium source. It is the combination of calcium extracted from milk and a class of mineral salts obtained after dehydration, degreasing, drying and spraying. Its ingredients include Calcium citrate 、 calcium phosphate 、 Ionic calcium 。 Milk calcium can be separated into ionic state without too much stomach acid in the human body, and then be directly absorbed and utilized by the human body, quickly regulating the blood calcium balance and strengthening the physique. Milk calcium is recognized as the food grade calcium supplement with the highest "bioavailability" among all calcium substances, because there is an appropriate amount of protein and a reasonable calcium phosphorus ratio of 2:1 in milk calcium, and because there is no chemical composition and process in its production process, there is no burden on the gastrointestinal tract. Therefore, milk calcium is the most suitable source of calcium supplement for infants, pregnant and nursing mothers, children and the elderly.

After looking at the calcium source, see the dosage form: there are more than 40 kinds of calcium nutrition enhancers allowed to be used. The dosage forms mainly include solid tablets, powders, granules, capsules, and liquid water, emulsions, etc. As solid calcium must be decomposed by gastric acid, calcium can be released from the complex into a soluble ionized state for easy absorption. Therefore, general solid calcium will cause stomach injury, gas production, nausea and other discomfort. In comparison, liquid calcium is easier to absorb and safer because the calcium ion dissociation process is simpler and more direct.

Small amount and multiple meals: according to the characteristics of "high intake, low absorption, low intake, high absorption" in the intestinal tract, calcium products should be taken in separate meals. The appropriate amount of calcium varies from person to person and from age to age. Generally, the amount of calcium for each meal is 50-100mg. It is recommended that infants and young children should not exceed 50mg per meal, and adults and pregnant women should not exceed 100mg per meal. And choose to take it between meals to reduce the interference of other foods.

Pay more attention to absorption and deposition: calcium deposition in bones is the final manifestation of calcium utilization in the human body. Due to the traditional technical difficulties, many calcium is still in the absorption stage. However, it only absorbs but does not deposit. It supplements a lot of calcium, but it does not work. The discovery of GK will usher in a new era for people's calcium nutrition, an era that pays attention to "calcium sinks into bone", and will really change the situation that "calcium cannot be replenished and sunk", so that calcium nutrition "can be replenished and sunk".

Appropriate dietary calcium intake of Chinese residents (mg/d)
Age (years)	AI	UL
0~	three hundred	—
0.5~	four hundred	—
1~	six hundred	two thousand
4~	eight hundred	two thousand
7~	eight hundred	two thousand
11~	one thousand	two thousand
14~	one thousand	two thousand
18~	eight hundred	two thousand
50~	one thousand	two thousand
Early pregnancy	eight hundred	two thousand
Second trimester	one thousand	two thousand
Late pregnancy	one thousand and two hundred	two thousand
wet nurse	one thousand and two hundred	two thousand

● AI (appropriate intake): It refers to the intake of certain nutrients of healthy people obtained through observation or experiment.

● UL (maximum tolerable intake): It refers to the maximum amount of a nutrient that can be ingested on an average daily basis. When the intake exceeds UL, the risk of toxic and side effects increases.

Reasonable calcium supplementation:

Calcium supplement and weight loss: When the blood calcium of the human body rises, it can increase the secretion of a hormone called calcitonin. Calcitonin, a hormone, can reduce people's appetite and reduce the amount of food they eat; In addition, sufficient calcium, especially Ionic calcium , in the intestinal tract fatty acid 、 cholesterol It can block the absorption of fat in the intestinal tract and make it excreted with feces. This method is more suitable for children to lose weight without any side effects.

Calcium supplement and blood pressure reduction: hypertension is a silent "killer", which is frightening, mainly because the disease has not produced any symptoms for many years, and it damages human arteries and blood vessels and other body organs in silence. Research shows that for some people, it may be an effective way to increase the intake of calcium without drugs.

For those who take 1300 mg of calcium every day, the incidence of hypertension is 12% lower than that of those who take 300 mg of calcium every day, and the risk of hypertension among people under 40 years old is 24% lower.

Supplement calcium to prevent heart disease: A large number of research data show that calcium can protect the heart by reducing blood pressure, as well as by helping reduce cholesterol in the blood.

Taking 2200 mg of calcium every day can reduce cholesterol by 6%, of which low-density lipoprotein cholesterol, which is the most harmful, is reduced by 11%, while the beneficial high-density lipoprotein cholesterol remains unchanged. In conclusion, experts have confirmed that cholesterol will improve as long as calcium intake is increased, whether through diet or supplements.

Calcium supplement to prevent myopia: myopia, an eye disease that endangers the eyesight of young people, will also "bow down" to calcium. Ophthalmologists tell people that if the eyeball is short of calcium, the intraocular pressure cannot maintain normal, just as the voltage will flash the bulb when it is high or low, causing myopia. Therefore, if sufficient calcium is added at the high incidence age of myopia - adolescence (specifically, the years from 11, 2 to 17, 8 years old), myopia is likely to be excluded from the body.

Supplement calcium to prevent abdominal pain: We often see such kind of children in life, who always cry for abdominal pain, neither fever nor diarrhea, and it is ineffective to kill insects. Moreover, abdominal pain can disappear by itself in a few minutes. This symptom may be related to intestinal spasm caused by calcium deficiency in the body. Since blood calcium is an important factor to maintain the normal excitation of neuromuscular, once it is low, the excitability of neuromuscular will increase, and the intestinal smooth muscle will produce strong contraction, which will cause abdominal pain. At this time, the treatment effect of "immediate effect" can be achieved by supplementing calcium.

Supplement calcium to prevent kidney stones: For many years, doctors have often reminded patients with kidney stones to limit their calcium intake, because calcium is one of the main components of stones. However, recent research shows that the way to reduce kidney stones may be to increase calcium intake. The tracking survey data of Dr. Cary C. Colhan of Harvard School of Public Health shows that:

Compared with the people who take the least amount of calcium (516 mg/day), the people who eat more calcium (1320 mg/day on average) have a 1/3 reduced risk of stone disease.

Calcium supplementation to prevent premenstrual syndrome: when eating a diet with high calcium content, 70% of women complained of pain relief, including back pain and cramps during menstruation; 80% urinary retention decreased; The frequency of crying, neuroticism or depression was reduced or alleviated in 90% of patients during the whole menstrual period.

Supplement calcium to promote height: how can children grow taller? Timely calcium supplementation is a simple and effective method. It is best to drink a glass of milk rich in calcium before going to bed at night. The secret lies in that after the child goes to sleep, endocrine system Most active and released growth hormone Most. And growth hormone is what children grow“ catalyzer ”At this time, a large amount of calcium is added to accelerate the calcification and maturation of new bones, which can be described as a "perfect match". The child will grow taller.

Calcium supplement to prevent cancer: calcium supplement helps prevent colon cancer. It may be that calcium can restrict bile acid from passing through the intestine. Another study confirmed that calcium can prevent the proliferation of colon polyps. Generally, the goal can be achieved by taking 1200 mg of calcium every day. The data showed that the rate of polyp regeneration in calcium supplements decreased by 24%.

Supplement calcium and prolong life: What's more exciting is that, Calcium element It may also be a nutrient for longevity. Italian longevity scholars made an interesting experiment: the rats were divided into two groups. Group A rats were fed with ordinary diet, with an average survival time of 89 days; The rats in group B were fed with 0.9% calcium, and lived 344 days, four times as long as those in group A. It is suggested that calcium deficiency is Life individual As an important factor of aging, calcium supplementation can make you live longer to some extent.

Calcium supplementation must be appropriate: Although calcium supplementation is very important to human health, it is still not recommended to supplement more than 2500 mg of calcium ion every day. Although excessive supplementation will not cause immediate poisoning, it will affect the absorption rate of other essential minerals such as iron and zinc. Calcium will chelate with tetracycline, reducing the activity of tetracycline, and calcium will also reduce the absorption of quinoline antibiotics. For example, during the treatment with such antibiotics, try to avoid taking drugs at the same time with calcium, or temporarily reduce the intake of calcium.

Osteoporosis Osteoporosis is a common disease characterized by decreased bone mass, degeneration of bone tissue microstructure and increased incidence of brittle fractures. Fragile fracture, namely osteoporotic fracture, is a low-energy fracture caused by self standing or lower height fall, which can occur when subjected to slight violence in daily activities, and is the most serious consequence of osteoporosis. Osteoporotic fractures can occur in all parts of the body, including the hip, leg, wrist, pelvis, spine, ribs, humerus, clavicle, radius and ulna. Foreign scholars have classified osteoporotic fractures into four categories: proximal femoral fractures, spinal fractures, and other major fractures (including pelvic fractures, distal femoral fractures, proximal tibial fractures, multiple rib fractures, and proximal humeral fractures) And secondary fractures (including fractures of the distal end of the upper limb and lower limb, such as forearm fractures, metacarpal or carpal fractures, rib fractures, fractures of the distal end of the lower limb, foot and clavicle fractures). Osteoporotic fracture of limbs refers to the above fractures occurring in other parts except spine and pelvis, and hip fracture and distal radius fracture are the most common.

Most patients with osteoporotic fracture of limbs are elderly. In China, the incidence of osteoporotic fractures in the elderly is 6.3% - 24.4%, and there are more elderly women. The incidence of male osteoporosis is also rising with age. Osteoporotic fractures of limbs have the following characteristics: more comminuted fractures, difficult reduction and fixation, internal fixators are easy to loose and fall off, and the risk of refracture is high; Fracture healing is slow and there is a high risk of complications during the healing process. Osteoporotic fractures have high morbidity and mortality rates, which affect the quality of life of patients and increase the burden of the health system. Therefore, actively treating osteoporotic fractures of limbs and restoring the function of affected limbs will help improve the quality of life of patients and reduce the medical burden of society.

Osteoporosis can be divided into three categories: the first category is Primary osteoporosis It is a physiological degenerative disease that occurs with the growth of age. This type can also be divided into two types. Type I refers to postmenopausal osteoporosis, which occurs in postmenopausal women, generally between 51 and 75 years old, and may occur earlier or later. Type Π is senile osteoporosis, which may be related to factors such as insufficient calcium intake, bone destruction and imbalance in the speed of new bone formation. It usually occurs after the age of 65. Long term drinking, smoking, insufficient calcium intake in diet, lack of outdoor activities and other bad living habits are more likely to cause osteoporosis. The second category is Secondary osteoporosis It is osteoporosis caused by other diseases or drugs. For example, chronic renal failure, endocrine diseases (especially thyroid, parathyroid or adrenal diseases, diabetes) and drugs (such as corticosteroids, barbiturates, anticonvulsants and excessive thyroid hormone). The third type is idiopathic osteoporosis, which is mostly seen in adolescents or adults aged 8-14 years. Many of them have a genetic family history, and women are more than men. Osteoporosis occurring during pregnancy and lactation can also be included in idiopathic osteoporosis.