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Calcium (Ca) | What we need to know

Calcium is the mineral most often associated with healthy bones and teeth, but it also plays an important role in blood clotting, helping muscles contract, and regulating normal heart rhythm and nerve function. About 99% of the calcium in the body is stored in the bones, the remaining 1% is in the blood, muscles and other tissues.

In order to carry out vital daily functions, the body regulates to maintain a constant amount of calcium in the blood and tissues. In particular, if the level of calcium in the blood is too low, parathyroid hormone (PTH) sends a signal to the bones to release calcium into the blood. This hormone can also activate vitamin D to improve calcium absorption in the gut.

At the same time, PTH signals the kidneys to excrete less calcium in the urine. When there is enough calcium in the body, another hormone called calcitonin does the opposite: It lowers calcium levels in the blood, stops calcium from being released from the bones, and signals the kidneys to excrete more through urine.

The body gets the necessary calcium in two ways. One is by consuming calcium-containing foods or supplements, and the other is by excreting calcium in the body. If a person does not eat enough calcium-rich foods, the body will release calcium from the bones. Ideally, the calcium that is "borrowed" from the bones will be replenished later. But this process does not always happen like this, and the accumulation of lost calcium cannot be achieved only by eating calcium-rich foods.

Recommended norms of calcium:

The daily norm of calcium depends on age. The average indicators are as follows:

  • up to 6 months - 200 mg
  • From 7 to 12 months - 260 mg
  • From 1 to 3 years - 700 mg
  • From 4 to 8 years - 1000 mg
  • From 9 to 13 years - 1300 mg
  • From 14 to 18 years old - 1300 mg
  • From 19 to 50 years - 1000 mg
  • From 51 to 70 years:
  • For men - 1000 mg
  • For women - 1200 mg
  • For pregnant and lactating women
  • For adults - 1300 mg
  • For adults - 1000 mg

Food sources:

  • Calcium is widely available* in many foods, not just dairy products, but calcium-rich foods include fruits, leafy greens, beans, nuts, and some starchy vegetables.
  • dairy products (cow, goat, sheep) and fortified vegetable milk products (almond, soy, rice);
  • cheese
  • yogurt;
  • Orange juice;
  • winter squash;
  • edamame (young green soybeans);
  • tofu, made with calcium sulfate;
  • canned sardines, salmon (with bones);
  • almonds
  • leafy greens.

Calcium bioavailability

Calcium is a large mineral and is not easily broken down in the intestines. Sometimes food labels list the amount of calcium, which is a measure of the calcium in the food, but not necessarily the amount that the body can absorb. The amount that is actually absorbed and used by the body is called "calcium bioavailability". Some foods have higher calcium bioavailability than others.

For example, dairy products have a bioavailability of about 30% absorption, so if a food label says 300 mg of calcium per cup, about 100 mg will be absorbed and used by the body. Plant foods, such as leafy greens, contain less calcium but have higher bioavailability than dairy products.

Signs of deficiency and toxicity

a) deficit

A more serious calcium deficiency Hypocalcemia. Caused by diseases such as kidney failure, operations on the digestive tract, drugs such as diuretics that interfere with absorption.

Symptoms of hypocalcemia:

  • muscle cramps, spasms;
  • acute pain in the muscles;
  • Tingling and relaxation in the tongue, hands, feet;
  • heart rhythm disorder;
  • irritability;
  • convulsions (tetany);
  • epileptic heart attack;
  • skin cracking, dryness;
  • breaking nails;
  • In many cases, the disease is asymptomatic.


To diagnose the disease, the endocrinologist conducts the following types of examinations:

  • general biochemical analysis of blood;
  • urine analysis;
  • electrocardiography;
  • X-ray examination of bones;
  • densitometry;
  • magnetic resonance imaging of internal organs;
  • special samples.


If the disease is not treated in time, the following complications may develop:

  • Osteoporosis;
  • Swelling of the optic disc;
  • Cataract
  • neuritis;
  • Hypoparathyroidism;
  • Heart failure;
  • Deformation of the skeleton.

Risk groups include:

  • Postmenopausal women – During menopause, the amount of estrogen in the body decreases, a hormone that helps absorb calcium and retain the mineral in bones.
  • Amenorrhea — a condition in which the menstrual cycle stops early or is disturbed, is often found in young anorexic women and in athletes who perform physical exercises with heavy loads.
  • Milk Allergy or Lactose Intolerance – Occurs when the body cannot absorb the sugar, lactose, or milk, casein, or whey proteins contained in milk.


Necessary treatment of the disease includes:

  • drugs containing calcium;
  • drugs containing vitamin D;
  • magnesium level-raising drugs;
  • Medicinal drugs can be prescribed both in the form of pills and injections after consultation with a doctor.

b) toxicity

An excessive amount of calcium in the blood is called hypercalcemia. The upper limit (UL) for calcium is 2500 mg per day from food and supplements. People over the age of 50 should not take more than 2000 mg per day, especially from supplements, as this may increase the risk of certain diseases, such as kidney stones, prostate cancer and constipation.

In some people, calcium can build up in the blood vessels at long-term high doses and cause heart problems. Calcium is also a large mineral that can block the absorption of other minerals such as iron and zinc.

Symptoms of hypercalcemia:

The disease is characterized by the following symptoms, which appear when the blood calcium level exceeds 11-12%:

  • Dehydration;
  • Frequent urination;
  • Heart palpitations, vomiting;
  • increase in blood pressure;
  • Loss of appetite;
  • severe pain in the abdomen;
  • muscle pain;
  • hallucination;
  • emotional disturbance;
  • decrease in mental activity;
  • rapid fatigue;
  • In many cases, the disease is asymptomatic.


If the disease is not treated in time, the following complications may develop:

  • atrioventricular blockade;
  • cardiac arrhythmia;
  • Acute renal failure;
  • convulsion
  • cardiac arrest;
  • Coma.


A type of blood test that measures the level of calcium in the blood is used to diagnose calcium deficiency or excess.
There are two types of calcium blood tests:
1)Total Calcium: This test measures calcium bound to certain proteins and "free" or unbound calcium in your blood.
2)Ionized Calcium: This test measures calcium that is not attached or "free" to certain proteins in your blood.

You can take the test at any branch of Synevo laboratories.

Online purchase of the test : 



For the prevention of the disease, it is recommended:

  • controlling intake of products rich in calcium;
  • People in the risk group should consult their doctor before using calcium and vitamin D supplements.


  • Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross AC, Taylor CL, Yaktine AL, et al., editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011. 5, Dietary Reference Intakes for Adequacy: Calcium and Vitamin D. Available from: Accessed 12/16/2019.
  • Dickinson HO, Nicolson DJ, Cook JV, Campbell F, Beyer FR, Ford GA, Mason J. Calcium supplementation for the management of primary hypertension in adults. Cochrane Database Syst Rev. 2006 Apr 19;(2):CD004639.
  • Kopecky SL, Bauer DC, Gulati M, Nieves JW, Singer AJ, Toth PP, Underberg JA, Wallace TC, Weaver CM. Lack of evidence linking calcium with or without vitamin D supplementation to cardiovascular disease in generally healthy adults: a clinical guideline from the National Osteoporosis Foundation and the American Society for Preventive Cardiology. Annals of internal medicine. 2016 Dec 20;165(12):867-8.



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