Calcium

Calcium is a macro (major) mineral.
Calcium is the most common mineral in the human body. About 99% of the calcium in the body is found in bones and teeth, while the other 1% is found in the blood. After age 30, the body gradually loses calcium, resulting in gradual depletion of bone minerals. The deficiency of vitamin D leads to absorption of calcium in less degree.

Why is Calcium important?

Calcium is a critical factor in maintaining a healthy skeleton. Low blood calcium levels lead to chronic kidney failure, vitamin D deficiency, and low blood magnesium levels. Calcium is essential for the formation of strong bones and teeth and for the maintenance of healthy gums. It increases the rate of bone growth and prevents against bone loss associated with osteoporosis. Vitamin D is required for optimal calcium absorption.

How much Calcium is enough?

Adults should have 1000 milligrams every day (ages 19-50 years).
Older adults (50 years and older) should have 1200 mg/day of calcium every day.

Intake:

Recommended Dietary Allowance (RDA) for Calcium
Babies 0 to 1 years	220 mg/day
Children 1 to 3 years	500 mg/day
Children 4 to 6 years	800 mg/day
Children 7 to 8 years	900 mg/day
Children 9 to 13 years	1300 mg/day
Teenagers 14 to 19	1200 mg/day
Adults ages 19-50 years	1000 mg/day
Adults 50 age and older	1200 mg/day
Pregnant women	1300 mg/day
Breast-feeding	1300 mg/day

Function:

Calcium plays a role relaxation of blood vessels, nerve impulse transmission, muscle contraction, and the secretion of hormones like insulin. Binding of calcium to the protein, calmodulin, activates enzymes that breakdown muscle glycogen to provide energy for muscle contraction.
    Calcium is essential for the formation of strong bones and teeth.
    Calcium is important in the maintenance of a regular heartbeat and transmission of nerve impulses. Calcium helps lower cholesterol levels and helps prevent against cardiovascular disease and certain forms of cancer including colourectal cancer.
    It is involved in the activation of several enzymes including lipase, which breaks down fats for utilisation by the body.

Sources:

Dairy products represent rich sources of calcium, but certain vegetables and grains also provide calcium. The kale, broccoli, bok choy, cabbage, mustard, and turnip greens are rich of calcium.

Food	Serving	Calcium(mg) in serving
Milk	8 ounces	300
Yogurt	8 ounces	300
Cheddar cheese	1.5 ounces	303
Chinese cabbage, cooked	1/2 cup	239
Spinach, raw	1/2 cup	175
White beans, cooked	1/2 cup	113
Spinach, cooked	1/2 cup	115
Pinto beans, cooked	1/2 cup	45
Red beans	1/2 cup	41
Broccoli, cooked	1/2 cup	35
Rhubarb	1/2 cup	174