Calcium and Bone Health

The correlation between dietary intake of calcium and the density and strength of the bones. Calcium is essential for proper bone structure, strength, and mass. The bones contain about 99 percent of the calcium in the body.

From before birth until about age 30, the body adds calcium and other minerals to bone tissue to increase bone mass and strengthen the skeletal structure. The skeleton reaches peak bone mass and strength in the late 20s. After age 30, bone mass begins to decrease. With increasing age after 30 the body’s ability to absorb dietary calcium diminishes.

Cigarette smoking and longterm excessive alcohol consumption accelerate the decrease. It is important for long-term bone health that peak bone mass be as high as possible. Regular weight-bearing exercise, such as walking and running, stimulates the growth of new bone tissue.

Bones: The Body’s Calcium Bank

Calcium is a vital mineral for many activities in cells throughout the body, including the conduction of nerve signals and the contraction of muscle cells. The body uses the calcium stores in the bones to meet its other needs for calcium when dietary intake does not meet those needs and calcium in the blood circulation drops.

Calcitonin and parathyroid hormone are the hormones that primarily regulate calcium transport between the blood circulation and the bones.

Without adequate calcium the bones can become dangerously thin and weak, making them susceptible to fracture under circumstances that otherwise would not harm the bones. The key health conditions of inadequate bone density are osteopenia and osteoporosis. osteoporosis is the leading cause of hip fracture in older adults, which often results in long-term disability or premature death.

Though loss of bone density with aging is inevitable, lifelong measures such as adequate calcium intake and daily weight-bearing exercise can maintain bone health and prevent osteoporosis.

The body must obtain calcium through dietary sources or supplements. The amount of calcium an individual needs changes across the spectrum of age. The years of adolescence are among the most vulnerable for inadequate calcium consumption because teens tend to drink much less milk and eat fewer dark green vegetables, the primary dietary sources of calcium in the American diet.

Calcium Intake Needs
AgeDaily Adequate Intake (AI) Amount of Calcium
birth to 3 years500 milligrams (mg)
4 to 8 years800 mg
9 to 18 years1300 mg
19 to 50 years1000 mg
51 years and older1200 mg

Natural dietary sources of calcium include dairy products (milk, cheese, yogurt), dark leafy vegetables such as spinach and broccoli, and tree nuts such as almonds and pecans. Many foods sold in the United States are calcium-fortified (contain added calcium).

They include orange juice, cereals, breads, soy milk, and soy products such as tofu. Low-fat dairy products, which have lower amounts of saturated fats, are the more healthful choice and contain just as much calcium as higher fat products. Labels on packaged foods in the United States state, per serving, the food’s calcium content and its percentage of the daily adequate intake (AI) amount.

Calcium Sources in Food

DIETARY SOURCES OF CALCIUM
Food SourceServing SizeAmount of Calcium per Serving
almonds3 ounces210 milligrams (mg)
blackstrap molasses1 tablespoon170 mg
bok choy (cooked)1 cup160 mg
broccoli (cooked)1 cup60 mg
canned salmon (with bones)3 ounces180 mg
canned sardines (with bones)3 ounces325 mg
clams (steamed)3 ounces80 mg
collards1 cup265 mg
cottage cheese1 cup155 mg
crab (steamed)3 ounces90 mg
hard cheese (cheddar, swiss)1 ounce225 mg
kale (cooked)1 cup95 mg
milk1 cup300 mg
mollusks (steamed)3 ounces80 mg
mozzarella cheese1 ounce200 mg
okra1 cup125 mg
provolone cheese1 ounce205 mg
raisins1 cup75 mg
rhubarb (cooked)1 cup345 mg
ricotta cheese1⁄2 cup335 mg
sauerkraut1 cup70 mg
spinach (cooked)1 cup245 mg
turnip greens (cooked)1 cup200 mg
yogurt8 ounces425 mg

Three forms of calcium are commonly available as dietary supplements: calcium carbonate, calcium citrate, and calcium phosphate. However, many doctors believe the form of calcium matters far less than maintaining adequate intake of calcium. Individuals have varying tolerances and responses to the different forms of calcium supplements.

Many doctors recommend calcium carbonate in the form of chewable antacid tablets as the most available, easiest to take, and least expensive calcium supplement product.

Because numerous factors influence how much calcium the gastrointestinal tract absorbs, health experts recommend obtaining as much calcium as possible through dietary sources with calcium supplementation to make up the difference.

Total calcium consumption that exceeds 2000 milligrams (mg) a day does not provide any added benefit and may cause health problems due to excessive calcium.

The body also requires vitamin D to absorb dietary calcium. The primary sources of vitamin D are sunlight and dietary supplements. The body can synthesize (make) as much vitamin D as it needs with adequate skin exposure to sunlight. However, many people do not get enough sunlight. Sun protection products, necessarily applied to protect against sunburn block the ultraviolet rays that activate vitamin D synthesis.

As well, there is not adequate ultraviolet light exposure during the winter months for people who live in the northern hemisphere in the United States, above a line roughly drawn from San Francisco to Boston. Because of these factors, most calciumfortified foods also contain supplemental vitamin D. Inadequate vitamin D causes softness of the bones-rickets in children and osteomalacia in adults regardless of calcium intake because the body cannot absorb calcium without vitamin D.

Though insufficient calcium intake is by far the more significant health issue because of the effect it has on bones, excessive calcium consumption has potentially serious adverse effects on the body systemically. Excessive calcium can cause arrhythmia (irregularity in the heart rate), muscle cramps, kidney stones (nephrolithiasis), and nerve disturbances.

See also CRAMP; DIET AND HEALTH; EXERCISE AND HEALTH; HYPERCALCEMIA; HYPERPARATHYROIDISM; HYPOCALCEMIA; HYPOPARATHYROIDISM; MINERALS AND HEALTH; PARATHYROID GLANDS; SMOKING AND HEALTH; VITAMINS AND HEALTH.

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