Calcium (diet)

Calcium[1] helps makes the bones and teeth stronger as well as playing a part in blood clotting.[2][3] Calcium is a dietary mineral. Inside the body (as dietary calcium) it is used as calcium ions in the form of chemical compounds. More than 99% of the calcium in the body is stored in bones,[3][4] which is stored and released using chemical signalling. Adults (aged 19-64) need 700mg of calcium a day, according to the NHS (National Health Service in the UK).[2] In the United States, the Food and Drug Administration (FDA) sets the recommended daily allowance (RDA) for adults and children over the age of 4 at 1,300mg.[5] Human beings can usually get the dietary calcium they need from eating a healthy, balanced diet.

Calcium is best known for keeping the teeth and bones strong. Other things that it does in the body is causing muscle contraction, including the heart muscle.[2] In the heart, contraction is called systole, and other muscles contract by getting shorter. In muscles it causes the contraction to stay on, because it affects the polarity (and flow of other minerals, like salt and potassium) of the cell. Calcium has a role in cells throughout the body including in nerves, and in pregnancy and apoptosis. It is tightly regulated and interacts with fluoride and phosphor in the blood and bones, plays a role in gut (intestine) health (interacting with other minerals such as magnesium there), and is relevant in some types of drug metabolism. Calcium also helps with blood clotting. Calcium is an inorganic part of the bone matrix, which includes other inorganic components like phosphate and hydroxide ions.[3]

Source

Dietary calcium is found in ample (enough) amounts in a balanced diet. Usually, humans can get enough calcium daily from diet alone, but people who are at risk or cannot eat a balanced diet can use supplements to get their recommended daily allowance (RDA). Taking more than 1,500mg of calcium a day can sometimes cause diarrhoea.[2] Usually, supplements are the cause of the body having too much calcium. 1,500mg or less of daily calcium is not likely to cause harm.[2]

Calcium can be found in foods like:[2][5]

Foods that have been fortified with calcium (called fortified foods) include flour. When fortified flour is used to make bread, it becomes a source of calcium.[6] Other fortified foods include cereals and anything made with fortified flour. In the United States, fruit juice drinks are fortified.[5] Fortified foods such as cereals, as well as dairy products, like milk and cheese, or yogurt,[5] are high in calcium which can be used by the body. The calcium absorption of these foods is around 30%.[5]

The source of calcium (from foods) changes how much of the calcium is used by the body. Calcium from milk, foods made from milk (such as cheese) and fortified foods are higher than in plant foods, and this is the same with some vitamins (such as vitamin A). Foods like plants or vegetables, such as leafy green vegetables, like Chinese cabbage or broccoli[5] or spinach,[2] are high in calcium but form (create) salt compounds which cannot be digested by the body.[5] Oxalic acid and phytic acid are two examples of compounds found in plants which interact with calcium to form salts that are not bioactive.[5]

The National Health and Nutrition Examination Survey in America found that some people get less calcium from their diet than they need then other groups of people. It found that black and Asian people living in America who are not hispanic and poor people are less likely than other people to be getting enough dietary calcium.[5] The same study found that in 2007-2010, 49% of children were not getting enough calcium, 39% of all people above the age of 4, from food or supplements in America.[5]

Other people that might not get enough calcium from diet include vegans or people who do not or cannot drink milk. People that are allergic to milk or have lactose intolerance might not get enough dietary calcium. This includes other people who might be at risk because of their race. In these people, lactose-free dairy products can supplement their diet so that it contains enough calcium that the body can use. Fish that are eaten with the bones are a source of calcium. These people might have to eat fortified foods fortified with calcium in order to reach their recommended daily limit and prevent negative side effects. After menopause, the lack of estrogen in the body causes it to not absorb calcium as well, or cause the body to lose more calcium.[5] In the United States and Europe, about 30% of these women have osteoporosis, and 40% or more of those with the condition get at least 1 bone fracture.[5] This is caused by the increased risk in falls and decreased calcium reabsorption. Compared to women, male increase in fracture risk from age-related bone loss happens 5-10 years later than in women.[5]

Low calcium

Too little calcium can cause osteoporosis, fragile bones, increased risk of falls, and increased bone fractures, but these are more commonly caused by a deficiency of vitamin D.[5] Hypoalbuminemia (low blood levels of a protein called albumin) might also look the same as low calcium levels in the blood.[7] Low calcium levels can also cause high blood pressure[8] (hypertension), like hypercalcaemia can. Falls and fractures are common in menopausal women because estrogen helps regulate bone formation and remodelling. Loss of bone density happens to older women during menopause[5] if estrogen levels are left unchecked (with an estrogen deficiency) which can cause pain and problems with mobility.[9] On average, 1% of the bone mineral density is lost per year in these people.[5] People with osteoporosis get fractured bones more often.[9] Low calcium can cause mild cramps.[7] People at risk of this are usually given hormones (hormone replacement therapy, often called HRT) or supplements to prevent bone loss and the problems caused by that. Low calcium also causes rickets in children and osteomalacia in children and adults, or other bone disorders in adults.[5]

Low blood serum levels of calcium (hypocalcaemia), measured as blood having less than 8.5mg/dL (mg per decilitre) (2.12mmol/L), or as an ionized calcium level of less than 4.61mg/dL (1.15mmol/L),[5] is usually caused by a deficiency in vitamin D or magnesium.[5] These levels can also be caused by hormonal imbalances, for example if the thyroid hormone (producing parathyroid hormone) is not working properly), causing hypoparathyroidism.[5] It can also be caused by low bone reabsorption or calcium reabsorption, medications or illness. Hypocalcaemia is another symptom of proton pump inhibitor drugs (PPIs), which lower the stomach acid, as well as cisplatin (chemotherapy medication) or bisphosphonate drugs which come as adverse effects.[5]

Hypocalcaemia can cause no symptoms (be asymptomatic), especially when the body is only slightly deficient or has been deficient for a long time. Because calcium affects most cells in the body, symptoms of not having enough can range widely between people.[5] Hypocalcaemia can cause neuromuscular irritability including muscle spasms, paraesthesia (tingling in the hands and feet), or perioral (around the mouth) numbness.[5][7] More serious signs and symptoms can include kidney injury, or calcification, brain calcification, congestive heart failure, cataracts,[7] paraesthesia (numbness or tingling of the fingers or toes),[7] seizures and rarely, coma. Low calcium levels can cause symptoms of mental illness such as depression, anxiety, or bipolar disorder too.[5][7]

Trousseau's sign, the symptom of the hands curling in, the wrists and fingers coming together and flexing tight, can also show when inflating a tourniquet or cuff (used to measure blood pressure).[7] This happens when there is too little calcium in the blood. It might show itself when pumping a cuff or applying a tourniquet to draw blood from the arm. Calcium levels are measured without a cuff, but one might be used to find a nerve and make it easier to put a catheter or needle into the arm (but the blood should not be taken without deflating the cuff).

SPASMOD IC: Mnemonic (for calcium deficiency)

A mnemonic for remembering what shows in calcium deficiency, using the first letters of SPASMOD IC:[7]

  • S - Spasms (Trousseau's sign being carpopedal spasms)
  • P - Perioral (around the mouth) parasthesiae (numbness)
  • A - Anxious, irritable, irrational (mental signs)
  • S - Seizures
  • M - In smooth muscle, an increase in muscle tone (which causes colic, wheeze, dysphagia)
  • O - Orientation impairment (orientation not working properly, like time, place, who the person is) and confusion
  • D - Dermatitis (for example atopic or exfoliative dermatitis)
  • I - Impetigo herpetiformis, happening during pregnancy, rarely, but serious. Causes lower calcium (and pustules, during pregnancy)
  • C - Chvostek's sign (twitching in the corner of the mouth during tests of the facial nerve, testing nerve over-excitement by tapping the parotid)

High calcium

High calcium intake increases the risk of one type of acquired kidney stone disease (renal calculi).[5] Eating too much calcium can cause stomach pain (abdominal pain) and diarrhoea.[2][7] Severe diarrhoea can cause the body to lose too much calcium and water, causing hypocalcaemia[10] and dehydration, and so can frequent (often) urination. High calcium can also cause constipation.[7] Magnesium also causes diarrhoea (and is used to cause bowel movements in medicine), and severe diarrhoea can also cause hypomagnesemia.[10] These can be an issue in some parts of the world, such as in developing countries, where there is a lot of diarrhoea.

Having too much calcium can also cause polyuria, also called frequent urination.[7] In addition to mental illnesses, which come from chronic (long-term) high calcium, for example depression, anxiety, and bipolar disorder, it can cause kidney stones and pyrexia (red skin). Kidney stones are extremely painful. Having too much calcium can cause ectopic (made in the place that it shouldnt be) calcification, like fluorosis. This makes bones form incorrectly. High calcium levels can cause weight loss, being tired, weak (weakness) and mental confusion. High calcium levels can cause hypertension[7] (high blood pressure), like low calcium can. It can also cause cardiac arrest (heart stopping, a type of heart attack), and hypercalcaemia shows on electrocardiograms (ECG) as a shortened QT interval, prolonged (longer) PR interval.

Some studies have shown that high calcium intake can make cardiovascular disease (CVD) more likely.[5] The amount of calcium needed depends on age, like the levels needed for it to be too high. These show that high calcium intake may also increase the risk of developing prostate cancer.[5]

Supplements

In America, women take supplements more than men (32% of women compared to 22% of men in the United States).[5] In the same country, 4-8% of children take a supplement.[5] Supplements can be used to treat low calcium levels or for other reasons.[5][11] A combination form of vitamin D with calcium exist, which contain less than the recommended amount of vitamin D at around 200-400 IU (international units) of vitamin D in these tablets.[12]

The dose for calcium supplements is 700mg, but can sometimes be as high as 1000-1300mg of calcium.[12] Taking less than 1,500mg (upper dose limit) of calcium supplements is unlikely to cause harm.[2]

Calcium regulation

Organisms need to keep calcium ion levels very well controlled. High calcium levels are bad, and low calcium levels are In the UK, the normal (physiological) level of calcium (total) in fats, or lipids, is 2.12-2.65mmol/L (millimoles per litre).[7] Tests for calcium levels in blood serum are taken while the patient is fasting (if the doctor has instructed them to be fasting), uncuffed.[7] The tourniquet or cuff can be used to get access to the vein, but it should be taken off before taking the blood sample.[7]

Calcium homeostasis is the level of calcium the body needs to keep working, which the body always tries to maintain. Some ways that calcium homeostasis can be maintained are:

  • Calcium is lost in urine. When there is too much calcium, the kidneys can filter it out and excrete it in the urine
  • Calcium moving in or out of bones
  • The thyroid gland is responsible for setting calcium homeostasis, as well as basal metabolic rate[3]
    • Calcium levels in the body are controlled by a thyroid hormone called calcitonin.[3] Calcium levels are lowered by calcitonin[3]

The control of calcium in the body is called calcium metabolism. The human body controls calcium levels with many hormones. Calcitonin, Parathyroid hormone (acronym PTH), and Vitamin D are the most important hormones in calcium metabolism. Vitamin D is a vitamin that works as a hormone and it is important in the body as it affects the formation of bones alongside calcium. Most people get enough vitamin D from diet, or have enough of the other vitamins if the glands are working properly. Vitamin D supplements exist, like calcium supplements, but have a higher risk of causing kidney stones than dietary vitamin D.[7] Calcitonin lowers the calcium levels in blood plasma by working with different organs and the bone. It increases calcium excretion from the kidneys, decreases absorption from the gut, and causes more calcium to be stored in bone.[3][7] When the blood calcium level is high, it stimulates the body, and causes more calcitonin to be excreted, which comes from the C-cells (parafollicular cells).[3] The role that calcitonin has in the body is not obvious.[7] C-cells are thyroid cells that are responsible for making calcitonin.[7] The creation of calcitonin causes a decrease in calcium in phosphate.[7] Opposite to calcitonin, parathyroid hormone raises calcium levels.[3] It is antagonistic to calcitonin,[3] which means it does the opposite things. It lowers the excretion of calcium by the kidneys while increasing bone resorption (which frees up calcium). This causes an increase in calcium. It does this also while making the gut absorb more calcium (by using vitamin D). The parathyroid hormone also causes a decrease in phosphate (as PO43-).[7] Like calcitonin being released when calcium is high, and levels decreasing when calcium goes down, when blood serum levels of calcium rise, the secretion of PTH is decreased.[3] PTH is secretion is triggered by a lowered amount of calcium ions in the blood serum and is controlled by a negative feedback loop,[7] because it makes the amount of calcium in the blood serum rise.[7]

: Ca2+ leaving the sarcolemma reticulum (SR), a type of modified, calcium containing smooth endoplasmic reticulum (SER), depolarizing it:

→ ∙ Acetylcholine (ACh) releases from motor neurons → acetylcholine receptors (also called AChRs) in sarcolemma activates
→ depolarization of sarcolemma → Transverse tubules (also called T−tubules) carry signal
→ Ca2+ leaves the sarcoplasmic reticulum (SR), causing depolarization → Calcium binds to troponin after depolarizing SR

During the latent period (the time between reaching the amount needed for muscle contraction and the muscle contracting), the action potential spreads across the muscle and allows calcium to be released (from the SR). If, or when, calcium is released from the sarcoplasm, it is allowed to relax,[3] because calcium is responsible for "holding" the contraction. A simple muscle twitch is the response to a smaller, brief stimulus (getting excited) either at or above the threshold.[3] It is made up of three stages, including the latent period. The other two stages after the latent period are the contraction and relaxation periods.[3]

Like how potassium is in a lot of ways the opposite of calcium when talking about cells or metal, phosphor is related when it is calcium and bones. The amount of calcium that is used or stored in bones is linked to the amount of phosphate in blood. Low levels of phosphate (hypophosphatemia) in the blood causes calcium to exit the bones, which then affects the bones negatively. Fluoride can cause bone problems because it acts in the same way as calcium, and leads to fluorosis. When there is too much fluoride in the body, bone formation can go unchecked as well as problems with the kidneys and blood pressure. Alongside calcium, sodium and magnesium, as well as potassium are stored in the bone.[3] Calcium is an inorganic component of the bone matrix, as well as hydroxide ions and phosphate.[3] When bones are being formed in the body, calcium as well as phosphate are sourced from the blood,[3] lowering blood calcium levels. Organic components of the bone structure include collagen, as well as glycoproteins and other peptides.[3]

Calcium in cells

Calcium ions are important to cells, but too many calcium ions can be bad. If a cell gets more calcium ion than it needs, it can die. This is why the amount of calcium ion in cells is highly regulated. At the same time, not enough calcium ion is bad. Cells must have the right amount to function properly. The normal (physiological) level of calcium (total) in fats, or lipids, is 2.12-2.65mmol/L (millimoles per litre). It is measured in the total plasmic Ca2 amount in blood serum (around 40% being together with albumin, and around 60%, or the rest, is free calcium in its ionized form).[7] Things that can affect calcium binding include cirrhosis (of the liver) and different proteins being in the myeloma.[7] The binding of calcium varies from person to person.[7]

Cells which use calcium for motility (plant cells also do this) do not usually have calcium move around after the cell has taken it in, and afterwards it is usually discarded. Calcium can bind to fat (called lipids) in the body.[5] Many cells have calcium channels on their membrane surface. These are openings (called invaginations) where calcium ions can enter the cell and do different things. Whether calcium or other minerals can enter the cell or not is dependent on the gate which is open or closed with electricity (polarization). The voltage difference between the inside and outside of the cell makes the voltage-gated channel open or closed, to allow calcium to enter or exit.

Once in the cell calcium ions activates many proteins to do specific things. For example, calcium goes into white blood cells and causes them to become motile, to help them move around and fight germs.[3] One type of cell that uses calcium are muscle cells, which includes cells in the heart muscle. When it goes into muscle cells, it makes them contract (shorten so the muscle pulls) and cause it to stay contracted. It could also be said that the opposite of calcium is potassium in cells, and potassium is used in making calcium metal for the same reason. In the body, calcium helps cells stay contracted, while potassium helps them release. The contents of the cell changing to push out or take in calcium and potassium changes its polarity, which allows the cells to keep working.

Nitrogen moieties can interact with the voltage-gated calcium channels (because nitrogen and calcium react with one another) and this is one way that compounds such as drugs can interact with the cell. Cyclic AMP (cAMP),[3] or adenosine monophosphate uses nitrogen to interact with cells in this way. Calcium levels increase, or cAMP levels change, in G-coupled receptors to change the polarity, which is used in nerves[3] as well as in drugs. Like cAMP and calcium, inositol triphosphate (IP3) is a chemical messenger.[3] All muscles are able to contract. Muscle contraction depends on calcium as well as ATP (adenosine triphosphate).[3] Depolarization of the muscle causes an action potential, which spreads throughout the muscles, and causes calcium (in the form of Ca2) to be released from the cell. As the action potential (signal) decays, the cells stop releasing calcium and start to take calcium back in.

Nerves

When calcium goes into nerve cells, it triggers electrical impulses that send a message called an action potential. Calcium channels open and allow for calcium to go into the nerve cells when the action potential reaches the nerve terminal.[3] Nerves waiting to be excited are stored in the membrane-bound (in membranes) vesicles.[3] This causes cell depolarization and makes an electrical connection with the reaction that is caused and the electrical conductivity of the mineral.

When the amount of calcium in these cells goes up very fast, the nerves on the vesicles that were waiting to be excited join together (fusion) with the cell membrane at the nerve synapse.[3] This fused vesicle membrane that is high in calcium can pass electricity between points because they are touching and filled with calcium. The membrane is filled with neurotransmitters (nerves).This causes the nerve to get excited, which is called exocytosis.[3]

Fertilization (pregnancy)

In human fertilization, the penetration of the sperm through the membrane of the egg (ovum) called the cortical reaction causes a release of calcium ions.[3] The amount of calcium ions increasing inside the cell depolarizes it, and increases the metabolic rate of the zygote (a diploid type of germ cell) so that it can grow. By depolarizing the cell, the calcium prevents fertilization from multiple sperm cells. The fertilized and depolarized egg is now called the fertilization membrane.[3] Twins come from two different ovum released during the ovulatory cycle being fertilized by two different sperm (which causes non-identical twins), or when a single zygote splits into two (causing identical twins).[3]

Apoptosis

Sometimes cells are unhealthy and need to die in for the body to replace them with new, healthy cells. This keeps the whole organism healthy. Cells know when they should die and can trigger reactions to end their life cycles in many ways. When this happens it is called apoptosis, also known as a 'programmed cell death' (planned cell death.) One way cells accomplish apoptosis by taking in toxic levels of calcium ions.

Health

Age-related bone loss occurs in both men and older women, around 5-10 years later in men.[5] Bone loss can cause osteoporosis or other disorders related to bone. Bone loss can cause rickets in children and osteomalacia in children and people over 4, and other bone-related problems in people over 4. Calcium deficiency increases the risk of bone fractures as well as falls.[5] These fractures can occur in the hip, vertebra and forearms.[5] A hip fracture in a young woman might not be normal (if her calcium levels are high), and bone fractures like these can be caused by an overactive parathyroid gland (releasing too much PTH), causing increased bone reabsorption and more fragile bones.[3] Cancer of the gland might also cause this. In this case the bones might reabsorb calcium from the blood even though levels are already high.[3] Studies have shown that people at risk of falls or bone fractures taking calcium supplements does not decrease their risk,[5] but can reduce bone density loss. The U.S. Preventive Services Task Force (USPSTF) showed with "moderate certainty" that calcium-vitamin-D supplements do not decrease the risk of fractures happening in postmenopausal women.[5]

Vitamin D is closely related to calcium. The ones also rely on vitamin D, which can cause problems with the bones. However, low levels of calcium can mask the signs of vitamin D deficiency as well as magnesium deficiency. When the body does not get enough calcium over a long period of time, or gets only slightly less than it needs, it can also cause no symptoms.

Medications can affect the calcium levels in the body. Calcium can also interact with medications.[5] Calcium-Vitamin-D supplements interacts with over 300 medications.[12] For example, it interacts with lithium (a treatment for bipolar disorder) and cause hypercalcemia when taken with calcium supplements, and calcium can interact with levothyroxine (a thyroid hormone, also used to treat thyroid cancer) and cause the drug to be absorbed by the body less.[5] It can interact with a HIV medication used by adults and children called dolutegravir, and cause the levels of the medication in the blood to lowered when taking calcium supplements.[5] Quinolone antibiotics become less effective when they are taken alongside (with) calcium supplements. Examples of quinolone antibiotics include ciprofloxacin, gemifloxacin, moxifloxacin.[5]

In a lot of studies, the difference between calcium gained from diet, and from supplements, has to be considered.[5] The difference in calcium from supplements or from eating foods can be significant, and shows that calcium may be different when it is taken in supplemental form like with vitamin D.

Heart (Cardiovascular)

Studies have shown that lower calcium intake is linked with some heart problems.[5] Low calcium can increase the risk of getting high blood pressure (hypertension), stroke, and thickening of the heart vessels called atherosclerosis.[5] The heart vessels might get narrower because their walls are thicker with cholesterol or plaque. However, in some of the studies, the increased risk is because calcium supplements were used, or that calcium supplements do not increase the risk.[5] Because calcium can join (bind) with fatty acids in the body, it can lower fat (lipids) absorption and then lower the risk of cardiovascular diseases (or CVD).[5] However some studies have shown that it actually increases the risk,[5] including risk of CVD.

Diets low in fat and or nonfat dairy products (like 0% milk, also called fat-free milk) and higher than the what the average diet in America has, lowered the systolic blood pressure by 5.5mmHg (millimeters mercury) on average. This meant that the pressure in the blood vessels when the heart was contracted was lower. This could mean that diets low in fat and high in calcium makes the blood pressure lower. The study showed the diastolic blood pressure (when the heart was contracted) was lower by 3.0mmHg on average when the diet was higher than the average calcium, and lower in fat (including from dairy).

Metabolic syndrome

Metabolic syndrome is a group of at least 3 risk factors for diabetes (which causes high triglyceride levels, high lDL (low density lipoprotein) high fasting (not eating) blood sugar levels (hyperglycemia), and a large waistline), and heart disease and stroke. Studies have shown that metabolic syndrome can be prevented by using calcium supplements, especially in women.[5] Studies showed that women (but less in men) had a lower risk of developing metabolic syndrome when they got their recommended dietary amount of calcium every day.[5]

Cancer

While calcium does not reduce the mortality of cancers like lung, breast, prostate or colorectal cancer, the risk of developing some types of cancer might be lowered by calcium. Though studies gave mixed results, some of them showed that the risk of developing colorectal cancer is lowered by calcium.[5] These results do not always agree with the studies done on calcium supplements. Calcium was seen to decrease the risk of colon cancer by 26% (587mg/day), but not rectal cancer.[5] These studies showed the risk going down by 8% with 300mg/d taken, or 16% with 600mg of increase of daily calcium intake.[5] Prostate cancer risk has been seen to increase with calcium taking in more calcium from diet, but only from dairy foods.[5] Dairy is one of the best sources of calcium, and plant-based sources are less bioavailable. Studies putting calcium together with ovarian cancer showed a lower risk in people getting enough calcium, but the study was not statistically perfect.

Pre-eclampsia

A risk during pregnancy is pre-eclampsia, which is hypertension and proteinuria (proteins in the urine) or thrombocytopenia.[5][13] Pregnant women who struggle to get enough calcium in their diet might lower their risk of getting pre-eclampsia[5] (which happens from the second half of pregnancy onwards, in 4% of the population of the United States), but studies showing this sometimes have problems with them. None of the studies for pre-eclampsia used vitamin D alongside the calcium supplements. Many professional or health organizations say that calcium supplements during pregnancy are good and can reduce the risk of developing pre-eclampsia or other related problems. Some examples are the American College of Obstetrics and Gynecology and World Health Organization (WHO). Studies were done in other parts of the world, or health organizations like the Canadian Hypertensive Disorders of Pregnancy Working Group (Canada), Society of Obstetric Medicine of Australia and New Zealand (Australia, New Zealand), including in Argentina, South Africa, and Zimbabwe for measuring the effect or benefit of calcium on preventing pre-eclampsia.

References

  1. ↑ "MeSH Browser". meshb.nlm.nih.gov. Retrieved 2026-04-11.
  2. 1 2 3 4 5 6 7 8 9 "Vitamins and minerals - Calcium". nhs.uk. 2017-10-23. Retrieved 2026-04-11.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Macnow, Alexander Stone; Kaplan Publishing, eds. (2024). MCAT Complete 7-book subject review 2025 -2026, set includes books, online prep, 3 ... practise tests. Fort Lauderdale, Florida: KAPLAN North America, LLC dba kaplan Publishing. ISBN 978-1-5062-9438-4.
  4. ↑ Yu, Elaine; Sharma, Sandeep (2026), "Physiology, Calcium", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 29489276, retrieved 2026-04-11
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 "Office of Dietary Supplements - Calcium". ods.od.nih.gov. Retrieved 2026-04-11.
  6. 1 2 "Food Fact Sheet: Calcium (Calcium facts)" (PDF). BDA/NHS. Archived from the original (PDF) on 2026-05-08. Retrieved 2026-04-11.
  7. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Oxford Clinical Handbook of Medicine (9th edition). ISBN 9780198844013.
  8. ↑ Iseki, K.; Massry, S. G.; Campese, V. M. (1986-05). "Effects of hypercalcemia and parathyroid hormone on blood pressure in normal and renal-failure rats". The American Journal of Physiology. 250 (5 Pt 2): F924–929. doi:10.1152/ajprenal.1986.250.5.F924. ISSN 0002-9513. PMID 3706544. {{cite journal}}: Check date values in: |date= (help)
  9. 1 2 "Menopause and Bone Loss". www.endocrine.org. 2022-01-24. Retrieved 2026-04-09.
  10. 1 2 Woodard, J. C.; Webster, P. D.; Carr, A. A. (1972-07-01). "Primary hypomagnesemia with secondary hypocalcemia, diarrhea and insensitivity to parathyroid hormone". The American Journal of Digestive Diseases. 17 (7): 612–618. doi:10.1007/BF02231747. ISSN 1573-2568.
  11. ↑ "Calcium". drugs.com. Archived from the original on 2025-12-15. Retrieved 2026-04-12.
  12. 1 2 3 "Calcium-VitaminD". drugs.com.{{cite web}}: CS1 maint: url-status (link)
  13. ↑ "Pre-eclampsia". nhs.uk. 2018-01-11. Retrieved 2026-04-12.
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