Food sources and facts of Calcium


Calcium is a naturally occurring most popular mineral that is an essential component of the human body. Calcium is about 40 percent of total body mineral weight and about 1.5 percent of total body weight. It is absolutely necessary in order for all the systems of the body to function properly. Furthermore, calcium tends to be portrayed as a hero for protecting the human body from osteoporosis. However, most people really do not understand how calcium functions. Calcium is found in foods and the body as an atom with a +2 charge (Ca++ or Ca2+). Calcium atoms, therefore, are most stable after they have given up two electrons. Due to this heavy positive charge, calcium  interacts with substances bearing a negative charge strongly. This allows it to form mineral complexes found in bone and teeth as well as interact with proteins to make things happen in certain cells.

There is a complicated regulatory process that keeps the blood level of calcium stable when a person is in good health. This involves the absorption of calcium from food, the storage of calcium in bone, the elimination of excess calcium in the urine, and the resorption of calcium into the blood from the bone if levels get low. A number of hormones and vitamins help regulate this process. The main hormone is called parathyroid hormone, and it is necessary for the body to maintain a normal calcium level. Vitamin D is also essential for the body to absorb and use calcium.

For most people, the level of calcium in the blood stays normal and never causes a problem. However, many people develop a deficiency of calcium in the bones as they age. They have not been ingesting enough calcium in their diet for years, and the body has used the calcium from bones to keep the levels up. Eventually, people low on calcium will have lower bone mass, as well as a deterioration of bone tissue. This is called osteoporosis. People can feel fine and be completely unaware of this problem until they break a bone or a doctor screens them for osteoporosis.

What Foods Provide Calcium to Our Diet?

Many foods have excellent and very good amounts of calcium. These include dairy products such as milk, yogurt, and mozzarella and cheddar cheese. Other foods with higher amounts of calcium include soymilk, sardines, fortified orange juice, tofu, fortified cereal, kale, and turnip greens. Still, many people do not obtain a sufficient amount of calcium from food. For them, taking daily supplementation is normally recommended. Calcium is usually sold as calcium carbonate or calcium citrate. In order to be absorbed, calcium carbonate requires stomach acid. Therefore, it needs to be consumed with food. Calcium citrate may be taken with or without food.

Food name Weight (g) Calcium (mg) DV%
Sesame seeds 144 1404 140%
Swiss cheese 132 1175 117%
Parmesan cheese 100 1109 110%
Mozzarella cheese 113 1086 108%
Winged beans 182 801 80%
Feta cheese 150 740 74%
Sorghum syrup 330 495 49%
Sheep’s milk 245 473 47%
Tofu 124 434 43%
Almonds 143 385 38%
Natto 175 380 38%
Collards 170 357 35%
Rhubarb 240 348 34%
Yogurt 170 338 33%
Lupins 180 317 31%
Amaranth grain 193 307 30%
Mungo beans 207 286 28%
Potatoes 200 284 28%
Hyacinth beans 210 273 27%
Turnip greens 164 249 24%


What Dietary Factors Can Influence Calcium Absorption?

Plants can contain substances called oxalates and phytate, which can bind to calcium in the digestive tract and decrease its absorption. It is estimated that as little as 5 percent of the calcium is absorbed from spinach because of the presence of inhibiting substances in the digestive tract.

Additionally, factors such as normal stomach acidity and presence of certain amino acids in  small intestine seems to enhance the efficiency of absorbing calcium. Because of this calcium supplements should be taken with a meal and the one with the least amount of vegetables. Furthermore, a diet having a higher phosphorus-to-calcium ratio may reduce calcium absorption and the ratio of phosphorus to calcium in the diet should not exceed 2:1.

What Are the Recommendations for Calcium Intake?

The Calcium intake recommendations according to NIH (National Institutes of Health) are listed below:

(Calcium in mg/day)
Infants to 6 months 210
Infants 6 to 12 months 270
Children 1 to 3 years 500
Children 4 to 8 years 800
9 to 18 years 1,300
Adult 19 to 50 years 1,000
Adults 50 years and older 1,200
Pregnant and lactating women:

18 years or younger

19 to 50 years


Health Benefits of Calcium Intake

After discovering information about Calcium, now let us know its health benefits in detail:

  1. Role in bone and teeth

Without question the most recognizable function of calcium is to make the bones and teeth hard. The two major calcium-containing complexes found in these tissues are Calcium Phosphate [Ca3(PO4)2] and Hydroxyapatite [Ca10(PO4)6OH2] with latter one being the most abundant. The structure of Hydroxyapatite crystals is somewhat similar to flagstone: basically long and flat. This design allows hydroxyapatite to lie on top of collagen fibers in bones and teeth, thereby accompanying the strength of collagen with rigidity and hardness

. Calcium phosphate slightly varies from hydroxyapatite that it is broken down more readily than hydroxyapatite, allowing it to serve as a resource of both calcium and phosphate to maintain blood levels of these minerals. Furthermore, calcium phosphate can be used to make hydroxyapatite in bones and teeth.

  1. Heart and Skeletal Muscle

Calcium involves in the function of excitable tissue (muscle and nerves). Before the heart can “beat,” special cells in a region of the heart known the sinoatrial node (SA node) must immediately initiate an electrical impulse which then stimulates the rest of the heart to contract. Calcium is fundamentally involved in initiating that impulse in the SA node. Calcium is also involved in the contraction of heart muscle, as well as contraction of skeletal muscle. In doing so calcium is the factor that initiates the physical action of heart beats and muscle movement.

  1. Activity of Nerves and Hormones

Neurotransmitters and hormones are the means by which cells in the body can communicate with each other. However, in order for these substances to provide this service efficiently, they must be released from glands and nerve cells at appropriate times. Calcium is involved in the release of several of these substances. Furthermore, calcium is essential for certain hormones to have an impact upon certain cells. This means that when some hormones interact with their receptors, the result is an increase in the calcium concentration in that cell. As the level of calcium increases in these cells it will then interact with specific proteins and evoke the desired effect in that cell. Calcium sometimes can act as a middleman or intermediate factor as hormones cause things to happen. Scientists sometimes call this a “second messenger” role, whereby the first messenger was the hormone itself.

  1. Blood clotting

Calcium is also involved in proper blood clotting. When a hemorrhage occurs, clotting factors in the blood become activated and ultimately a clot is formed at the site of the hemorrhage. A clot is somewhat analogous to a bicycle tire patch that is placed specifically to seal off a hole. The clotting process consists of many steps, which requires calcium to proceed. Calcium binds to the clotting factors and allows it to become more active. Therefore, with a less than optimal amount of calcium in the blood, it might take longer to stop a hemorrhage. factors and allows them to become more active. Therefore, with a less than optimal amount of calcium in the blood, it might take longer to stop a hemorrhage.

  1. Treat osteoporosis

Calcium can help to both prevent and treat osteoporosis. Most people do not get enough calcium in their diet. The questions are, when should people take supplemental calcium, how much should they take, and how long should they take it? All of these questions are being tested in clinical trials. It is accepted that adequate calcium intake is necessary for healthy bones, but it is a complicated process, not just related to how much calcium a person ingests.

  1. Weight loss

There have been studies that showed that people, who ingest a lot of calcium containing dairy products while they diet, or take supplemental calcium, may lose more weight than people who do not. This may only be true for calcium in dairy products and not in supplements. Or it may not be true at all. Data gathered while a group of people was taking calcium for treatment of osteoporosis indicated that those taking more calcium tended to weigh less. However, a review of nine studies containing data on weight and calcium ingestion was conducted, and there was little evidence that dairy products or calcium supplements had an effect on weight or fat mass. Studies need to be done to specifically address this question.

  1. Lowers chances of Colon cancer

Calcium is related with preventing cancer and studies have shown people consuming adequate amounts of calcium to the diet helps to lower colon cancer. When adequate calcium is used, remainder is free to bind to waste material along its transit out of the body by inactivating carcinogenic waste compounds. It is known as chelating agent used for binding and neutralizing toxins.

  1. Kidney stone prevention

Calcium helps to prevent kidney stones. Kidney stones are calcium but not typical supplemental calcium. Literally, kidney stones are calcium oxalate crystals considered to be due more to calcium found in tap water jointly with metabolites of certain foods. Calcium carbonate or calcium gluconate are able to bind with residues which form oxalate crystals in kidney and promote its excretion. It boils down to use correct form of calcium to improve kidney health.

  1. Lower PMS symptoms

Symptoms which occur while flowing menses make this monthly period worst time for most of the women. In this case, calcium helps to minimize and lower these effects. Believed that due to interactions between Vitamin D, calcium and hormones estrogen and progesterone, which are considered to be modulated by it.

  1. Cure for Type 2 diabetes

Study have shown that 20000 nurses found that supplementation of calcium daily have lower chances of developing diabetes than those who did not have calcium supplement. In question the dose was 1200 mg regularly splited in 2 daily doses.

What Are The Impacts of Calcium Deficiency on Bone Health?

The human body does everything it can to keep the amount of calcium in the blood within a normal range. If enough calcium is not ingested in food or supplements, the body will start pulling calcium out of the bones. It will also allow less calcium to leave the body in urine. If all the hormones in the body are working properly, including a high enough level of vitamin D, the level of calcium in the blood will be normal.

One cause of hypocalcemia, which means low calcium in the blood, is hypoparathyroidism. This means the parathyroid glands are not working properly. The parathyroid glands are in the neck, on either side of the thyroid gland, around the level of the Adam’s apple. The parathyroid glands can be removed accidentally during thyroid surgery. They can be infiltrated by cancer. There are genetic (inherited) conditions that can cause low parathyroid hormone.

There are other problems that affect calcium metabolism. Inadequate levels of vitamin D or abnormal levels of magnesium can contribute to low calcium levels. The kidneys also play a role in keeping the amount of calcium in the blood constant. Research has shown that there are many more factors regulating calcium level than were previously identified, in terms of other minerals, cofactors, and vitamins.

The most common problem associated with actual calcium deficiency is osteoporosis. A person will feel fine and not suspect anything is wrong, until one fractures a bone. Any condition in which the level of calcium in the blood is low (hypocalcemia) can be very dangerous. If the calcium level gets very low, multiple body systems will start to malfunction, from the nerves and muscles to the heart and brain. Many symptoms occur because of malfunction of nerves and/or muscles, called neuromuscular irritability. These include:

  • Muscle cramps
  • Muscle twitches
  • Muscle spasms
  • Numbness
  • Abnormal sensations
  • Seizures
  • Spasm of the larynx (voicebox), leading to trouble breathing
  • Spasm of the bronchial tubes, also leading to trouble breathing
  • Tetany, which is a lot of these symptoms together with muscle spasm and aching

A person with hypocalcemia can have a change in brain function. Low calcium can cause the heart muscle to fail. It can also cause arrhythmias—abnormalities in the way the heart beats. A person with very low calcium can have depression, dementia, and even psychosis. If this goes on long enough, there can be swelling in the brain, cataracts in the eye, and permanent heart damage. Very low calcium levels can be fatal.

Is Calcium Toxic in Large Amounts?

Today, it is fairly common for people to take in more calcium than years gone by because of supplementation practices and the large number of calcium-fortified foods. Based on this it is possible for people to exceed the AI. Though the efficiency of calcium absorption decreases as more is ingested and body calcium status is optimal, this can still lead to increased entry of calcium into the body. The Upper Limit (UL) has been set at 2,500 milligrams for children and adults, a level that is usually only achieved with the assistance of supplementation. Beyond this intake level the risk of undesirable effects increases, and can include loss of appetite, nausea, vomiting, constipation, abdominal pain, dry mouth, thirst, and frequent urination. In addition, since most forms of kidney stones are calcium oxalate, higher levels of calcium in the urine can increase the risk of kidney stones in people prone to them. Very high intakes of calcium from supplements and usually in combination with calcium-containing antacids, over time, can lead to increased calcium content in tissues such as muscle (including our heart), blood vessels, and lungs. This will affect the activity of the tissues by making them more rigid.


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