Medically reviewed by
Sara Osman,RD,PT
Introduction
Calcium is the most abundant mineral in our bodies and it makes up 1.9% of the body by weight. [1,2]
The body gets calcium in two ways, either by eating calcium-rich foods or supplements or by drawing calcium from the body or bones specifically. [4]
The borrowed calcium from bones is usually replaced at a later stages when the nutrient levels go up, but it might not happen always. [4]
Calcium salts provides rigidity to the skeleton whereas calcium ions help in the metabolic process. [2]
Different hormones work with the kidney to control the calcium reserves in the body as well as excretion. [4]
In case of calcium deficiency, the body will remove calcium from the bones. [4]
- Ingested calcium is mixed with digestive juice calcium to be absorbed in the proximal small intestine. [2]
Net absorption percentage increases with intakes and peaks at 35% at an intake of 400 mg and then falls off as intake increases further. [2] - Net calcium absorption declines with ageing. It could be as high as 60% in infants and young children but decrease to 15-20% in adulthood and so forth. [1]
- However, certain anti-nutrients like oxalates and phytates can bind to calcium and decrease its bioavailability. [3,4]
- Almost 99% of the calcium is stored in the bones and teeth. [1,3]
- The remaining 1% is used by the body for nerve transmission, muscular function, intracellular signalling and other such important functions. [1]
- Bone mineral serves as the ultimate reservoir for the calcium circulating in the extracellular fluid.[2]
- When calcium levels drop in the blood, certain hormones signal the bone to release more calcium in the bloodstream, activate vitamin D to improve absorption of calcium in the intestines and reduce calcium excretion in urine. [4]
- Some of the absorbed calcium is excreted from the body in urine, faeces and sweat. [1]
- The average calcium losses in excretion are estimated to be around 240 mg/day. [7]
Body Functions
Recommended Daily Intake
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Deficiency Symptoms
Calcium Food Sources
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Excessive Intake/ Toxicity Side Effects
Groups At Risk of Calcium Deficiency
Calcium Interaction With Other Nutrients
- Vitamin D – Vitamin D intake improves calcium absorption. [1]
- Iron and Zinc – High calcium intake can possibly interfere with the absorption of iron and zinc. High calcium phosphate intake (1,360 mg/day) may decrease zinc absorption. [1,3]
- Sodium – High sodium intake increases urinary calcium excretion as it is believed that sodium competes with calcium for reabsorption in renal tubules. [1,2]
- Protein – High protein intake, especially animal protein and certain grains (acid ash protein) may increase urinary calcium excretion
and is therefore thought to negatively affect calcium status. [1,2,3,6]
One study found that 0.85 mg of calcium was lost for each gram of protein in the diet. [2] - Magnesium – Magnesium deficiency may be a result of high calcium intake. [3] Calcium intakes in excess of 2600 mg/day have shown to decrease magnesium absorption.[3]
- Oxalic and Phytic acid – Foods rich in oxalic or phytic acid may inhibit calcium absorption. [3]
Nutrient Profiles For Food Groups
Medically reviewed by
Sara Osman,RD,PT
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