The importance of calcium in skeletal health is well established in the scientific literature, and the nutrient’s popularity as a supplement is justifiable. More than 99% of the calcium in the body is contained in bones and teeth and hard bone is comprised of around 90% calcium. It is worth noting that calcium helps maintain bone density by more than just its role in the structural composition of bone tissue. Healthy bone tissue is not inert – it is constantly being built up and broken down in order to ensure a balance between proper skeletal integrity and blood calcium levels. Calcium stimulates the release of the thyroid hormone calcitonin, which causes calcium to be taken from the blood to replenish levels in bone tissue. This action is intended to work in balance with phosphorus, a mineral that stimulates parathyroid hormone release, which in turn causes calcium to be taken from the bone in order to elevate blood calcium levels. Rickets (involving impaired growth and bone malformation in children) and osteomalacia (soft bones in adults) are a direct consequence of a long-term deficiency of calcium in the diet. Calcium supplementation affords considerable protection to bone health, as demonstrated in numerous studies. For example, in postmenopausal women, a review of the research indicates that supplementation with 1000-1700mg per day significantly reduces the rate of bone loss and is associated with a reduced incidence of osteoporotic fractures.


Calcium also plays an essential part in the proper function of the muscular system. In particular, calcium is needed for the contraction phase of muscle function, while the mineral magnesium facilitates the relaxation phase. Calcium is required in order for ATP (adenosine triphosphate) to be hydrolysed into a form that can be used as energy to fuel the contraction of muscle tissue. Also relevant to muscle function is the influence of calcium in neurotransmitter activity and transmission of nerve impulses. Muscle contraction serves many critical purposes in bodily function ranging from the voluntary, such as body movement, to the involuntary, such as pumping of blood and the movement of food through the digestive system.


The activation of the nervous system is regulated by chemical messengers known as neurotransmitters. The concentration of calcium in the terminal membrane of the nerve cell will dictate the quantity of certain neurotransmitters to be released. The end result of calcium’s neurotransmitter influence is less sensitivity and irritability in the nerves. Tetany (manifesting in muscle spasms and twitches due to hypersensitive nerves) is linked with calcium deficiency.


There is evidence, albeit inconsistent, that calcium may serve a beneficial purpose in cardiovascular health by reducing the risk of high blood pressure. It appears from epidemiological research that a high level of dietary calcium is associated with a lower risk of hypertension. However, studies suggest that calcium supplementation primarily only lowers blood pressure in black people and individuals who’s blood pressure is elevated by increased salt intake. Excessive cellular sodium can lead to increased blood pressure; although the role of magnesium and potassium is more significant, calcium works with these minerals to pump sodium from cells. There is also evidence that calcium can reduce the risk of hypertension in pregnant women. This is particularly relevant to women suffering with the condition known as preeclampsia (in which potentially dangerous elevation of blood pressure is a factor).


The proper clotting of blood is also dependent on a sufficient level of calcium in the body. For example, calcium is required for the formation of blood platelets, which provide “stickiness” or aggregation in the clotting process. Calcium also facilitates the production of fibrin, an insoluble protein that provides a sort of cap over a clot. Finally, calcium helps activate the clotting compound prothrombin.

Potential Applications

  • Osteoporosis
  • Osteomalacia
  • Rickets
  • Fractures
  • Bone health (general)
  • Dental health (general)
  • Muscle spasms and twitches
  • Leg cramps
  • Nervous tension
  • Irritability
  • Hypertension
  • Preeclampsia
  • Acid stomach (as an antacid)
  • Excessive lead levels
  • Histamine detoxification

Typical Supplemental Dosage Range

• 500-1500mg per day

Common Supplement Forms/Sources

Calcium amino acid chelate Calcium ascorbate Calcium carbonate Calcium citrate Calcium citrate/malate Calcium gluconate Calcium hydroxyapatite Calcium lactate Di- and tri-calcium phosphate Bone meal calcium Dolomite

  • Oyster shell calcium
  • Common Food Sources
  • Dairy products Nuts Carob
  • Sunflower seeds Sesame seeds
  • Greens (mustard, collard, turnip)
  • Broccoli Brewer’s yeast Figs (dried)
  • Kale Cabbage
  • Leafy green vegetables

Contraindications/Cautions/lnteractions/Toxicity Concerns

•       In order to avoid an increased risk of calcium deposition in the soft tissues (including kidney stones), daily dosages should be lower than 2000mg.

Please note: Certain experts believe that ensuring adequate magnesium intake and using calcium in the citrate form would lower the risk of soft tissue deposition. Research suggests that this is certainly the case for kidney stone formation.

•       Cancer patients and people with hyper-parathyroid disorder should not use calcium supplements unless on the advice and under the strict monitoring of a physician.

•       Calcium supplements should not be taken with blood pressure lowering drugs unless under medical supervision, as it may compound the effect of the drugs – in the case of calcium channel blocking anti-hypertensives, calcium may interfere with the drug’s action.

•       Calcium supplements should not be taken with digitalis unless under medical supervision.

•       Calcium may decrease the absorption of various drugs such as bisphosphanates (etidronate), fluoroquinolone antibiotics, 4-quinolones, tetracyclines and fluoride. It is recommended that calcium is taken at least two hours away from administration of the drug.

•       Taking calcium with the drug tamoxifen may lead to excessive blood calcium levels.

•       Strict medical supervision is required if patients taking cardiac glycosides receive parenteral calcium administration (the combination may increase the risk of heart arrhythmias).

•       Unless vitamin C is taken at the same time, high dose calcium may reduce iron absorption.

Agents/Factors Which Deplete Levels, Impair Absorption and/or Inhibit Activity

  • Caffeine
  • Oxalates (i.e. in spinach, cocoa,
  • Coffee
  • swiss chard, rhubarb, beet greens)
  • Tea
  • Aluminium-containing antacids
  • Alcohol
  • Fluoride
  • Sugar
  • Laxatives (long-term use)
  • Tobacco
  • Phosphates
  • Loop diuretics
  • Anti-convulsant drugs
  • High protein diets
  • Phytates (i.e. in whole grains)

Possible Signs/Symptoms Associated with Deficiency

•       Rickets

•       Osteomalacia

•       Osteoporosis

•       Increased risk of fracture

•       Poor tooth formation

•       Dental caries

•       Impaired growth

•       Muscle spasms and twitches (e.g. tetany)

•       Leg cramps

•       High blood pressure

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