& Joannie Dobbs Wednesday,
How much is too much calcium?
Skeletal thinning and the risk of osteoporosis increase as a person ages. Wishing to prevent this painful and debilitating condition, many people are taking calcium in the form of a dietary supplement. Many others are considering supplements. The decision is complicated because so many foods are now fortified with calcium.
Question: How much calcium does a person need?
Answer: The adequate intake value for calcium set by the Institute of Medicine is 1,000 milligrams per day for men and women age 19 through 50. After 50, recommended intake increases to 1,200 mg per day. From age 9 to 18, the recommendation is 1,300 mg per day.
Q: Does a person need the calcium daily?
A: Getting adequate calcium daily is best in the long run. Although the skeleton may seem like a fixed structure, its mineral components are constantly being broken down and rebuilt. On days when inadequate calcium is consumed, there will be a net loss of calcium from the bones. If this occurs often, the skeletal reserve will diminish over time and bones will weaken.
Q: Does a person need to take a calcium supplement to get enough calcium?
A: Not necessarily, it depends on the amount of calcium-rich foods in the diet.
Q: What are the best sources of dietary calcium?
A: Until recently, milk and milk products were recognized as the richest sources of readily absorbed calcium. Today, however, many processed foods contain the 300 mg of calcium found in one cup of milk.
One cup of calcium-fortified orange juice or V8 vegetable juice contains 300 mg or more per cup; soy and rice milks fortified with added calcium contain a similar amount.
Almost any breakfast cereal labeled "for women" has at least 300 mg of calcium per serving. Apparently the makers of Total assume you have no other source of calcium in your diet. One serving (3/4 cup) contains 1,000 mg. And for those with a sweet tooth, calcium-fortified chocolate candies have 300 mg calcium per piece.
Q: Can a person get too much calcium?
A: Yes. The Institute of Medicine indicates that the tolerable upper intake level for calcium is 2,500 mg per day. Consuming fortified foods and a calcium supplement could easily take you over that limit.
Q: What problems are associated with exceeding the limit?
A: Excessively high calcium intake over time may lead to kidney problems. Kidney stones are associated with both low and high calcium intake. Very high intake can cause kidney failure. Too much calcium can interfere with the absorption of minerals such as iron, zinc and magnesium.
Also, supplements in the form of calcium carbonate can neutralize stomach acids which, in turn, can impair the absorption of vitamin B-12 from natural food sources.
Q: How can someone get plenty of calcium, but avoid getting too much?
A: Do some basic accounting. Carefully check the nutrition facts labels for all the foods and dietary supplements you eat and add up your daily calcium intake.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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