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Food manufactures are adding calcium to a wide variety of foods lately - breakfast cereals, waffles, canned spaghetti, fruit juice, soymilk and margarine, to mention a few.
Now that calcium is in so many foods, are you getting enough or too much? Are calcium-fortified foods a good bargain or would it be less expensive to eat non-fortified foods and take a calcium supplement? Can you consume all the calcium you need at one meal or should you spread it out during the day?
Calcium's most notable role in the human body is to build and maintain strong bones and teeth. But it is also plays an important role in blood coagulation and muscle contraction. Calcium also has the potential to reduce the risks of osteoporosis, hypertension and colon cancer.
Nearly one-half of United States children do not consume enough calcium. Calcium is especially important during the teenage years because bone mass develops rapidly between the ages of 10 and 20 and peaks by age 30.
Americans spend more than 10 billion dollars each year repairing some 1.3 million fractures resulting from osteoporosis - the brittle bone disease. This complex condition is a major debilitating disease in the United States, affecting one in four women older than 45 and one in eight men older than 60. One's chances of surviving a broken hip or wrist are good, but many survivors are incapacitated.
| Recommended Daily Calcium Intakes |
| Ages |
Milligrams per day |
| Birth-6 months |
210 |
| 1-3 |
500 |
| 4-8 |
800 |
| 9-18 |
1,300 |
| 19-50 |
1,000 |
| 51+ |
1,200 |
| Pregnant or lactating |
| 14-18 |
1,300 |
| 19-50 |
1,000 |
*National Academy of Sciences
Calcium intake in excess of 2,500 milligrams is considered unsafe, as at these levels it can interfere with the absorption of other nutrients and, over time, could increase the risk of kidney stones.
Food seems to be the best source of calcium for the body. This is because other nutrients in the food source - vitamin D, for example - may positively affect the body's ability to absorb and use calcium.
Eat high-calcium foods throughout the day rather than all at one time. It seems that your body can efficiently absorb about 500 milligrams at one time, regardless if it comes from food or a supplement.
Other dietary factors that affect calcium levels include fiber, sodium, caffeine, alcohol, oxalic acid, protein and vitamin D. High levels of fiber can negatively affect calcium absorption. High levels of protein, sodium, caffeine and alcohol can increase the excretion of calcium in urine.
Oxalic acid found in spinach, chard and beet greens binds up the calcium present in these foods, making it unavailable for the body to use. It doesn't, however, affect the absorption of calcium in foods served at the same meal. And the good news about chocolate, another source of oxalic acid, is that it doesn't seem to tie up the calcium in milk, so go ahead and enjoy chocolate milk.
Vitamin D is needed for proper absorption of calcium. Regular exposure to sunlight, along with drinking vitamin D fortified milk, will meet the vitamin D needs of most young people. This may not, however, be sufficient for some older people. Vitamin D supplements that provide 600 to 800 IU per day have been shown to improve calcium balance in elderly people. It is important to take vitamin D supplements under the supervision of a physician or dietitian, as too much - more than 1,000 IUs per day - can be toxic for infants and more than 2000 IUs per day can be toxic for adults.
Because so many factors have the potential to affect our body's use of calcium, we might ask what is more important - the amount of calcium in a food or how well it will be absorbed? It is more important to focus on increasing total calcium intake. This means when choosing foods, calcium content generally is more important than the calcium bioavailability.
How much calcium is in my food?, you might ask. To find the answer, read the Nutrition Facts Label on most packaged foods. The label indicates what percentage of 1,000 milligrams per day the food product contains. The math for this nutrient count is easy - just add a 0 to the percent value. For example if one serving of the product contains 30 percent of the daily value, it contains 300 milligrams of calcium, about the amount found in an eight-ounce glass of milk.
As for foods that don't feature Nutrition Facts Labels (meat, and fresh fruit and vegetables), here's a short list.
| Approximate Calcium (mg)* |
| 1/2 cup Bok choy, cooked or fresh |
80 mg |
| 1/2 cup Okra |
50 mg |
| 1/2 cup Mustard greens |
50 mg |
| 1 medium Orange |
50 mg |
| 1/2 cup Kale, cooked |
45 mg |
| 1/2 cup Broccoli |
45 mg |
| 1/2 cup Turnip greens |
100 mg |
| 1 oz. Sardines with edible bones |
90 mg |
| 3 oz. Salmon, canned with edible bones |
205 mg |
*Source: American Dietetic Association's Complete Food and Nutrition Guide
Calcium-fortified foods can help us meet our dietary goals, but if the fortified food is substantially more expensive than the non-fortified version or if it otherwise is nutritionally empty (for example, calcium-fortified cookies, pop or chips), choose other foods and consider purchasing a calcium supplement.
or contact your local
Colorado State University Extension office.
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