Calcium: Enough Already?

Sept. 2, 2004 — -- The words "ADDED CALCIUM" are splashed on the labels of many food products, from bread to orange juice to soft drinks. But all that added calcium may not provide much health benefit -- in fact, it may cause some harm.

"Manufacturers will put in whatever amount of nutrients will help sell their product," said Lora Sporny, a professor of nutrition at Columbia University in New York. "But we have to recognize that there's a downside to all this calcium supplementation."

Calcium is an important nutrient, aiding the body in bone development, nerve function, muscle contraction, and blood clotting. In addition to its role in preventing osteoporosis, calcium may also help prevent PMS.

Most dietary experts agree that 1,000 mg of calcium daily is sufficient for healthy individuals under the age of 50. Over the age of 50, 1,200 mg per day is recommended.

"The real problem with calcium," said Sporny, "is that when too much gets dumped into your digestive tract, it affects absorption of other nutrients. The two most important nutrients are iron and zinc."

Ironically, those women who are most conscientious about their diets may be the ones most at risk. Because calcium blocks absorption of iron and zinc, women who have diets high in calcium are often deficient in these two important minerals.

"Women of childbearing age need enough calcium for bone mineralization," Sporny said. But if these women over-fortify their diets with calcium supplements, "day after day they become iron deficient."

Calcium intake is also an issue for the elderly.

"Calcium use has been shown to cause zinc deficiencies in elderly people," said Dr. Sattar Hadi, assistant professor of medicine at Vanderbilt University's Center for Human Nutrition in Nashville, Tenn. "That needs to be studied more thoroughly."

The easy availability of over-the-counter supplements is another issue. "A lot of time, patients don't get the information they need for taking these OTC supplements, and may not know how they interact with one another," Hadi said.