Calcium, today's "hot vitamin," is causing concern among health experts about the potential harm it and other vitamins and minerals can cause when taken indiscriminately.
There has been a tenfold increase in calcium supplement intake by Americans since 1980, when vitamin companies rang up $17 million in sales. Today's figure exceeds $125 million and some estimate that $160 million comes closer.
General concerns about health and new interest in an old disease, osteoporosis, are thought to be behind the boost in calcium supplement promotion.
"Interest in the important problem is fine, but interest in supplementation is negative," said Dr. Robert P. Heaney, professor at John A. Creighton University in Omaha, Neb., who specializes in bone and mineral research and calcium absorption. Heaney was speaking at a recent symposium on vitamin pills versus food, sponsored by members of the California Dietetic Assn. and the Dairy Council of California.
Heaney's concern is founded on recent research which shows that an increasing number of other substances may be hampered when calcium is taken in excess.
"In addition with supplements, you are getting a high dose of calcium, rather than the natural balance of many nutrients found in food. This dosage may in turn upset the balance of other nutrients in the body, such as iron and zinc," Heaney said.
Heaney pointed out that when supplements are consumed, other substances, such as carbonate, gluconate, lactate and citrate--whose long-term effects we still know nothing about--also are consumed. "In fact, you are getting a lot more of those chemicals than you are of calcium," Heaney said.
Osteoporosis, associated with calcium deficiency, is a disease of decreased density of the skeletal mass, causing fractures and minor injuries. However, according to Heaney, calcium deficiency does not necessarily cause osteoporosis. "Osteoporosis has many syndromes. It is not a single disorder."
Heaney cited several reasons for calcium loss problems: unbalanced Vitamin D status, high protein intake, high sodium intake, high fiber intake (fiber, it seems, interferes with absorption of calcium) and high caffeine intake.
And now, it is thought that aluminum-containing antacids (calcium carbonate), which make up about 75% of the calcium supplement market, may also block phosphorus absorption.
Heaney thinks the best channels for proper calcium absorption is through different food sources, including tofu, navy and pinto beans, collard greens, kale, broccoli, almonds, sardines and salmon (with bones), as well as milk, which contains calcium phosphate, one of the minerals needed for bone formation.
Milk also contains lactose, a sugar that aids in the absorption of calcium, as well as Vitamin D, which also is critical for calcium absorption. Milk products, in fact, are responsible for 75% of the calcium intake of Americans, although calcium is found in many foods.
About two or three 300-milligram servings a day of dairy products provide nutrient needs for calcium for adults. The recommended intake is 800 milligrams for average adults, but as much as 1,000 milligrams is recommended for pre-menopausal women. Pregnant women, lactating mothers and teen-agers require four servings, and pregnant and nursing teen-agers require five servings to allow for the needs of still-growing teen-agers as well as child.
Sardines also are an excellent source of calcium. Cream soup, cottage cheese, ice cream, tofu, salmon with bones, baked beans, bok choy, collard, mustard and turnip greens, waffles and pancakes also are lower in calcium content (about 150 milligrams per serving) but help contribute calcium to the overall day's intake.
Heaney and a colleague compared the effects of dairy calcium to those of the supplement calcium carbonate, which is commonly found in antacids. Results showed that milk and other dairy products seem to interfere less with the bone-renewal process than the antacid.
The renewal process, called "remodeling," is the continuous breakdown and rebuilding of bone, which goes on throughout one's lifetime.
"Genetic composition is an important factor in the size and quality of bone. We also have to consider the load one puts on bone. The bone can atrophy as muscles do if one does not exercise throughout life, " Heaney said.
With decreased utilization of calcium by the body, adequate nutrition is important only in a helping to maintain existing bone mass. "It won't cause more bone to develop, it will keep existing bone from depleting," Heaney said.
Cheryl Loggins, California Dietetic Assn. president, also told the 200 dietitians attending the symposium to be wary of recommending vitamin and mineral supplements to clients.
According to Loggins, 40% of Americans take supplements daily, and of these, nearly 11% take five or more pills a day, setting the stage for consuming toxic levels of vitamins and minerals.