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Sources of Calcium

Food
Milk, yogurt, and cheese are rich natural sources of calcium and are the major food contributors of this nutrient to people in the United States [1]. Nondairy 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 in Table 2.

Table 2: Selected Food Sources of Calcium [2-4]
Food Milligrams (mg)
per serving
Percent DV*
Yogurt, plain, low fat, 8 ounces 415 42
Sardines, canned in oil, with bones, 3 ounces 324 32
Cheddar cheese, 1.5 ounces 306 31
Milk, nonfat, 8 ounces 302 30
Milk, reduced-fat (2% milk fat), 8 ounces 297 30
Milk, lactose-reduced, 8 ounces** 285–302 29–30
Milk, whole (3.25% milk fat), 8 ounces 291 29
Milk, buttermilk, 8 ounces 285 29
Mozzarella, part skim, 1.5 ounces 275 28
Yogurt, fruit, low fat, 8 ounces 245–384 25–38
Orange juice, calcium-fortified, 6 ounces 200–260 20–26
Tofu, firm, made with calcium sulfate, ? cup*** 204 20
Salmon, pink, canned, solids with bone, 3 ounces 181 18
Pudding, chocolate, instant, made with 2% milk, ? cup 153 15
Cottage cheese, 1% milk fat, 1 cup unpacked 138 14
Tofu, soft, made with calcium sulfate, ? cup*** 138 14
Spinach, cooked, ? cup 120 12
Ready-to-eat cereal, calcium-fortified, 1 cup 100–1,000 10–100
Instant breakfast drink, various flavors and brands, powder prepared with water, 8 ounces 105–250 10–25
Frozen yogurt, vanilla, soft serve, ? cup 103 10
Turnip greens, boiled, ? cup 99 10
Kale, cooked, 1 cup 94 9
Kale, raw, 1 cup 90 9
Ice cream, vanilla, ? cup 85 8.5
Soy beverage, calcium-fortified, 8 ounces 80–500 8–50
Chinese cabbage, raw, 1 cup 74 7
Tortilla, corn, ready-to-bake/fry, 1 medium 42 4
Tortilla, flour, ready-to-bake/fry, one 6? diameter 37 4
Sour cream, reduced fat, cultured, 2 tablespoons 32 3
Bread, white, 1 ounce 31 3
Broccoli, raw, ? cup 21 2
Bread, whole-wheat, 1 slice 20 2
Cheese, cream, regular, 1 tablespoon 12 1

* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The DV for calcium is 1,000 mg for adults and children aged 4 years and older. Foods providing 20% of more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet. The U.S. Department of Agriculture’s Nutrient Database Web site lists the nutrient content of many foods. It also provides a comprehensive list of foods containing calcium.
** Calcium content varies slightly by fat content; the more fat, the less calcium the food contains.
*** Calcium content is for tofu processed with a calcium salt. Tofu processed with other salts does not provide significant amounts of calcium.

In its food guidance system, MyPyramid, the U.S. Department of Agriculture recommends that persons aged 9 years and older eat 3 cups of foods from the milk group per day [5]. A cup is equal to 1 cup (8 ounces) of milk, 1 cup of yogurt, 1.5 ounces of natural cheese (such as Cheddar), or 2 ounces of processed cheese (such as American).

Dietary supplements
The two main forms of calcium in supplements are carbonate and citrate. Calcium carbonate is more commonly available and is both inexpensive and convenient. Both the carbonate and citrate forms are similarly well absorbed, but individuals with reduced levels of stomach acid can absorb calcium citrate more easily. Other calcium forms in supplements or fortified foods include gluconate, lactate, and phosphate. Calcium citrate malate is a well-absorbed form of calcium found in some fortified juices [6]. The body absorbs calcium carbonate most efficiently when the supplement is consumed with food, whereas the body can absorb calcium citrate equally effectively when the supplement is taken with or without food [7].

Calcium supplements contain varying amounts of elemental calcium. For example, calcium carbonate is 40% calcium by weight, whereas calcium citrate is 21% calcium. Fortunately, elemental calcium is listed in the Supplement Facts panel, so consumers do not need to calculate the amount of calcium supplied by various forms of calcium supplements.

The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorption decreases. Absorption is highest in doses ?500 mg [1]. So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day.

Some individuals who take calcium supplements might experience gastrointestinal side effects including gas, bloating, constipation, or a combination of these symptoms. Calcium carbonate appears to cause more of these side effects than calcium citrate [1], so consideration of the form of calcium supplement is warranted if these side effects are reported. Other strategies to alleviate symptoms include spreading out the calcium dose throughout the day and/or taking the supplement with meals.

Medicines
Because of its ability to neutralize stomach acid, calcium carbonate is found in some over-the-counter antacid products, such as Tums® and Rolaids®. Depending on its strength, each chewable pill or softchew provides 200 to 400 mg of elemental calcium. As noted above, calcium carbonate is an acceptable form of supplemental calcium, especially for individuals who have normal levels of stomach acid.

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