Chief functions

▪ Bones and teeth – the primary function of calcium is in the development and maintenance of healthy bones and teeth

▪ Blood clotting – necessary for normal blood-clotting mechanisms that begin wound healing

▪ Blood pressure – helps maintain normal blood pressure

▪ Enzymes and hormones – essential for the production and activity of numerous enzymes and hormones that regulate digestion, energy and fat metabolism, and the production of saliva

▪ Membranes – aids in the transport of nutrients and other substances across the cell membrane

▪ Muscle contraction – works with magnesium in the normal contraction of muscles, including the heartbeat; a balance needs to exist between calcium, sodium, potassium, and magnesium to maintain muscle tone

▪ Nerve transmission – essential for normal transmission of electrical impulses along nerves

Possible benefits

▪ Cancer – might offer some protection against cancer of the colon

▪ Heart disease – might lower blood cholesterol and reduce risk of heart disease

▪ Weight loss – may play a role in fat metabolism, which aids in losing fat weight

▪ Low intake of calcium may increase the risk of chronic problems unrelated to bone health

Deficiency symptoms

▪ Rickets

▪ Osteomalacia or osteoporosis

▪ Periodontal disease

▪ Tetany (painful spasms of the muscles)

▪ Hypertension

Toxicity symptoms

▪ Calcium deposits into soft tissues, such as kidneys or heart

▪ Constipation

▪ Increased risk of kidney stone formation

Nutrient-nutrient reactions and absorption

▪ Absorbed in the small intestine with the help of vitamin D

▪ 10%-40% of dietary calcium is absorbed

▪ Absorption is reduced with:

– Excessive intake of oxalates and phytates

– Presence of fiber in the diet

– Fat malabsorption or high-fat intake

– Intake of alcohol, coffee, sugar, diuretics, and aluminum-containing antacids

– Stress

▪ Absorption is higher in times of greatest need, such as adolescent growth spurt, lactation, and pregnancy

▪ A greater percentage of dietary calcium is absorbed when the diet is high in protein, although a diet too high in protein can increase calcium excretion in the urine

▪ The presence of lactose enhances calcium absorption

▪ A more acidic environment favors the solubility of calcium, thereby increasing absorption

▪ A high intake might reduce zinc and iron absorption, and impair vitamin K metabolism

▪ Calcium works with magnesium, zinc, fluoride, and phosphorus to form and maintain bones and teeth

▪ Calcium competes with zinc, manganese, magnesium, copper, and iron for absorption in the intestine

DRI mg Tolerable Upper Limits
0-0.5 year 210 ND
0.5-1 year 270 ND
1-3 years 500 2500 mg
4-8 years 800 2500 mg
9-13 years 1300 2500 mg
14-18 years 1300 2500 mg
19-50 years 1000 2500 mg
51-70 years 1200 2500 mg
Pregnant 1000 2500 mg
Lactating 1000 2500 mg

DRI=Dietary Reference Intakes


ND=not determined

Tolerable upper limits are not determined for certain age groups, because of the lack of data of adverse effects and the concern with regard to lack of ability to handle excess amounts.

Dietary sources

▪ Best – dairy products, such as milk, ice cream, cheese, and yogurts; and canned fish with the bones

▪ Good – dark-green leafy vegetables, broccoli, cottage cheese, cooked dried beans, and peas

Groups at highest risk for deficiency

▪ Individuals who do not or can not consume dairy products

▪ The elderly

▪ Patients who have undergone gastric bypass surgery or have had part or most of their stomach removed because of disease

Other facts

▪ Most abundant mineral – 99% in the bones and teeth

▪ Fifth most abundant substance in the body

▪ Average healthy male contains 2.5-3 pounds (lb) of calcium

▪ Average healthy female contains 2 lb of calcium