Calcium, the most abundant mineral in the body, is found in some foods, added to others, available as a dietary supplement, and present in some medicines (such as antacids). Calcium is required for vascular contraction and vasodilation, muscle function, nerve transmission, intracellular signaling and hormonal secretion, though less than 1% of total body calcium is needed to support these critical metabolic functions. Serum calcium is very tightly regulated and does not fluctuate with changes in dietary intakes. The body uses bone tissue as a reservoir for, and source of calcium, to maintain constant concentrations of calcium in blood, muscle, and intercellular fluids.

The remaining 99% of the body's calcium supply is stored in the bones and teeth where it supports their structure and function. Bone itself undergoes continuous remodeling, with constant resorption and deposition of calcium into new bone. The balance between bone resorption and deposition changes with age. Bone formation exceeds resorption in periods of growth in children and adolescents, whereas in early and middle adulthood both processes are relatively equal. In aging adults, particularly among postmenopausal women, bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis over time.

What is Calcium ?
Calcium is essential to maintaining total body health. Your body needs it every day not just to keep your bones and teeth strong over your lifetime, but to ensure proper functioning of muscles and nerves. Calcium deficiency is usually due to an inadequate intake of calcium. When blood calcium levels drop too low, the vital mineral is "borrowed" from the bones. It is returned to the bones from calcium supplied through the diet. The average person loses 400 to 500mg of calcium per day. If an individual's diet is low in calcium, there may not be sufficient amounts of calcium available in the blood to be returned to the bones to maintain strong bones and total body health. Taking calcium regularly is key to preventing and treating calcium deficiency.
Where it is found
Milk, yogurt, and cheese are rich natural sources of calcium. Non-dairy sources include vegetables, such as chinese cabbage, kale, and broccoli. Most grains do not have high amounts of calcium unless they are fortified, however, they contribute calcium to the diet because they contain small amounts of calcium and people consume them frequently. Foods fortified with calcium include many fruit juices and drinks, tofu, and cereals. Selected food sources of calcium are listed below:


Milligrams (mg)
per serving

Percent DV*

Yogurt, plain, low fat, 8 ounces



Sardines, canned in oil, with bones, 3 ounces



Cheddar cheese, 1.5 ounces



Milk, nonfat, 8 ounces



Milk, reduced-fat (2% milk fat), 8 ounces



Milk, lactose-reduced, 8 ounces**



Milk, whole (3.25% milk fat), 8 ounces



Milk, buttermilk, 8 ounces



Mozzarella, part skim, 1.5 ounces



Yogurt, fruit, low fat, 8 ounces



Orange juice, calcium-fortified, 6 ounces



Tofu, firm, made with calcium sulfate, ½ cup***



Salmon, pink, canned, solids with bone, 3 ounces



Pudding, chocolate, instant, made with 2% milk, ½ cup



Cottage cheese, 1% milk fat, 1 cup unpacked



Tofu, soft, made with calcium sulfate, ½ cup***



Spinach, cooked, ½ cup



Ready-to-eat cereal, calcium-fortified, 1 cup



Instant breakfast drink, various flavors and brands, powder prepared with water, 8 ounces



Frozen yogurt, vanilla, soft serve, ½ cup



Turnip greens, boiled, ½ cup



Kale, cooked, 1 cup



Kale, raw, 1 cup



Ice cream, vanilla, ½ cup



Soy beverage, calcium-fortified, 8 ounces



Chinese cabbage, raw, 1 cup



Tortilla, corn, ready-to-bake/fry, 1 medium



Tortilla, flour, ready-to-bake/fry, one 6" diameter



Sour cream, reduced fat, cultured, 2 tablespoons



Bread, white, 1 ounce



Broccoli, raw, ½ cup



Bread, whole-wheat, 1 slice



Cheese, cream, regular, 1 tablespoon



See Calcium related videos:
video icon Dr Whiting on Calcium, Absorption, and Osteoporosis(video module - 7.48 minutes)
video icon How Much Calcium ?

Product related PDF file
The Calcium Channel

Benefits / uses
Bone health and osteoporosis
Bones increase in size and mass during periods of growth in childhood and adolescence, reaching peak bone mass around age 30. The greater the peak bone mass, the longer one can delay serious bone loss with increasing age. Everyone should therefore consume adequate amounts of calcium and vitamin D throughout childhood, adolescence, and early adulthood. Osteoporosis, a disorder characterized by porous and fragile bones, is a serious public health problem for more than 10 million U.S. adults, 80% of whom are women. Osteoporosis is most associated with fractures of the hip, vertebrae, wrist, pelvis, ribs, and other bones. Supplementation with calcium plus vitamin D has been shown to be effective in reducing fractures and falls in institutionalized older adults.

When calcium intake is low or ingested calcium is poorly absorbed, bone breakdown occurs as the body uses its stored calcium to maintain normal biological functions. Bone loss also occurs as part of the normal aging process, particularly in postmenopausal women due to decreased amounts of estrogen. Many factors increase the risk of developing osteoporosis, including being female, thin, inactive, or of advanced age; smoking cigarettes; drinking excessive amounts of alcohol and having a family history of osteoporosis.

Although osteoporosis affects individuals of all races, ethnicities, and both genders, women are at highest risk because their skeletons are smaller than those of men and because of the accelerated bone loss that accompanies menopause. Regular exercise and adequate intakes of calcium and vitamin D are critical to the development and maintenance of healthy bones throughout the life cycle.

Cardiovascular disease
Calcium has been proposed to help reduce cardiovascular disease risk by decreasing intestinal absorption of lipids, increasing lipid excretion, lowering cholesterol levels in the blood and promoting calcium influx into cells. In the Iowa Women's Health Study, higher calcium intake was associated with reduced ischemic heart disease mortality in postmenopausal women.

Blood pressure and hypertension
Several clinical trials have demonstrated a relationship between increased calcium intakes and both lower blood pressure and risk of hypertension Other observational and experimental studies suggest that individuals who eat a vegetarian diet high in minerals (such as calcium, magnesium, and potassium) and fiber and low in fat tend to have lower blood pressure. The Dietary Approaches to Stop Hypertension (DASH) study was conducted to test the effects of three different eating patterns on blood pressure: a control "typical" American diet; one high in fruits and vegetables; and a third diet high in fruits, vegetables, and low-fat dairy products. The diet containing dairy products resulted in the greatest decrease in blood pressure

Cancer of the colon and rectum
Several studies have found that higher intakes of calcium from foods (low-fat dairy sources) and/or supplements are associated with a decreased risk of colon cancer. In a follow-up study to the Calcium Polyp Prevention Study, supplementation with calcium carbonate led to reductions in the risk of adenoma (a nonmalignant tumor) in the colon, a precursor to cancer, even as long as 5 years after the subjects stopped taking the supplement. In two large prospective epidemiological trials, men and women who consumed 700-800 mg per day of calcium had a 40%-50% lower risk of developing left-side colon cancer.
In the Women's Health Initiative, a clinical trial involving 36,282 postmenopausal women, daily supplementation with 1,000 mg of calcium and 400 IU of vitamin D3 for 7 years produced no significant differences in the risk of invasive colorectal cancer compared to placebo.

Weight management
Several studies have linked higher calcium intakes to lower body weight or less weight gain over time. Two explanations have been proposed. First, high calcium intakes might reduce calcium concentrations in fat cells by decreasing the production of two hormones (parathyroid hormone and an active form of vitamin D) that increase fat breakdown in these cells and discourage fat accumulation.

When To Take/Types To Take
Calcium supplements are best taken with meal. Since calcium cannot be absorbed without vitamin D, better supplements will include it. A daily intake of 400-600 IU of vitamin D would be ideal. Most experts agree that magnesium should also be present.
Which form of calcium is best? There is no simple answer to this question since there are many effective options. Some research has found that approximately the same level of absorption can be attained with various forms of calcium (including calsium citrate, clacium carbonate, hydroxypatite, calcium gluconolactate, and calcium pidolate), while other research has shown that certain forms of calcium (such as calcium citrate) are better absorbed over other forms (such as calcium gluconolactate and carbonate). Still other reserach shows that even calcium carbonate (a relatively insoluble form of calcium) is fairly well absorbed when taken with a meal.







0-6 months*

200 mg

200 mg



7-12 months*

260 mg

260 mg



1-3 years

700 mg

700 mg



4-8 years

1,000 mg

1,000 mg



9-13 years

1,300 mg

1,300 mg



14-18 years

1,300 mg

1,300 mg

1,300 mg

1,300 mg

19-50 years

1,000 mg

1,000 mg

1,000 mg

1,000 mg

51-70 years

1,000 mg

1,200 mg



71+ years

1,200 mg

1,200 mg



Possible Side effects / Precautions / Possible Interactions:
Excessively high levels of calcium in the blood known as hypercalcemia can cause renal insufficiency, vascular and soft tissue calcification, hypercalciuria (high levels of calcium in the urine) and kidney stones. However, hypercalcemia rarely results from dietary or supplemental calcium intake; it is most commonly associated with primary hyperparathyroidism or malignancy.

Calcium supplements have the potential to interact with several types of medications. This section provides a few examples. Individuals taking these medications on a regular basis should discuss their calcium intake with their healthcare providers.
arw Calcium can decrease absorption of the following drugs when taken together: biphosphonates (to treat osteoporosis), the fluoroquinolone and tetracycline classes of antibiotics, levothyroxine, phenytoin (an anticonvulsant), and tiludronate disodium (to treat Paget's disease).

arw  Thiazide-type diuretics can interact with calcium carbonate and vitamin D supplements, increasing the risks of hypercalcemia and hypercalciuria.

arw  Both aluminum- and magnesium-containing antacids increase urinary calcium excretion. Mineral oil and stimulant laxatives decrease calcium absorption. Glucocorticoids, such as prednisone, can cause calcium depletion and eventually osteoporosis when they are used for months.
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