AMERICANS DON`T get enough of it and doctors have long undervalued it, but calcium may be on its way to becoming the wonder drug of the 1980s.
Growing evidence indicates that millions of people may be paying a high price for the national epidemic of calcium deficiency.
This deficiency underlies one of the most debilitating chronic diseases of the 20th Century, the brittle bone disease known as osteoporosis, and new research now links calcium deficiency to other common deadly diseases such as high blood pressure, heart disease, strokes, colon cancer and possibly other disorders of abnormal cell metabolism.
”We`re just suddenly realizing that a nutrient that we never thought a whole lot about could be causing some of the more common diseases that we deal with,” said Dr. David McCarron of the Oregon Health Sciences University.
The average adult body contains 2.5 pounds of calcium and 99 percent of it is tied up in bones and teeth, providing them with their mechanical and structural properties.
The other 1 percent circulating in the blood, however, is what makes life possible. So important is this 1 percent, that the body indiscriminately robs calcium out of the bones to ensure a supply for its critical chemical wizardry. It is this chronic bone depletion that eventually leads to osteoporosis.
”Calcium is the universal trigger by which all cells turn on their machinery,” said Dr. Robert Heaney, of Omaha`s Creighton University. ”Ten years ago calcium was thought to be a relatively minor mineral. Now it is being recognized as one of the most important minerals involved in good health.”
Calcium is the body`s metabolic jack-of-all trades. It carries nerve signals, contracts muscles, clots blood, keeps the heart running smoothly, regulates hormone secretions and helps enzymes do their vital jobs.
The first major disorder linked to calcium deficiency was osteoporosis. The bone-thinning disease affects an estimated 15 to 20 million Americans, causing 1.3 million fractures each year and costing the nation $3.8 billion annually.
In 1984, a National Institutes of Health consensus panel cited calcium deficiency as a major cause of the silent osteoporosis epidemic and recommended that Americans dramatically increase their calcium intake.
The panel said that the average adult American`s usual daily calcium intake of 450 to 550 milligrams was woefully inadequate and fell far below the 800-milligram daily intake recommended by the National Academy of Science`s National Research Council.
But, even the NRC`s recommended daily allowance may not be enough to prevent osteoporosis, said the panel, which recommended 1,000 milligrams daily for adult women and 1,500 for postmenopausal women.
The NRC is currently reviewing all of its vitamin and mineral recommendations and reportedly favors raising the daily calcium intake for women to 1,000 milligrams.
”It seems likely that an increase in calcium intake to 1,000 to 1,500 milligrams a day beginning well before the menopause will reduce the incidence of osteoporosis in postmenopausal women,” the panel said. ”Increased calcium intake may prevent age-related bone loss in men as well.”
The main source of calcium is milk (skim milk has as much calcium as whole milk) and dairy products. Other sources include dark green leafy vegetables such as collards, turnip greens, spinach, and broccoli, salmon, sardines, oysters and soybean curd. The panel recommended calcium supplements for people who do not get enough of the mineral in their diets.
Increased calcium intake could have an unexpected bonus in helping to prevent some of the other major disorders that have recently been linked to calcium deficiency, according to researchers. The new findings include:
— The first demonstration that calcium may be able to reduce the risk of colon cancer by reversing the abnormal behavior of cells lining the colon.
— A significant decline in high blood pressure to near normal levels among 44 percent of a group of mild to moderate hypertensives given calcium supplements. One-third of hypertensives may be able to control their high blood pressure simply by taking calcium.
— A study of Wisconsin farmers showing that drinking hard water containing calcium could reduce a person`s risk of dying of a heart attack or stroke by 10 percent.
”There`s been an explosion of information surrounding the role of calcium in the pathogenesis (cause) and treatment of diseases that span most of the disciplines of medicine at this point,” said McCarron.
A great deal more research needs to be done but the evidence is increasing that widespread dietary calcium deficiencies as well as genetically caused errors in calcium metabolism may underlie many of these disorders, he said.
When millions of people in a society suffer from the same types of disorders, that suggests that there may be a common cause, such as calcium deficiency, said McCarron.
”You wouldn`t wipe out osteoporosis, hypertension or colon cancer with more calcium but it could certainly have a potentially favorable impact on all three of them,” he said. ”These three important disorders are not the last we`re going to hear about that are related to calcium intake.”
While most experts agree that increased calcium consumption in the range of 1,000 to 1,500 milligrams daily is safe, some are concerned that even this level may promote kidney stone formation in people who are prone to forming stones. Certainly, calcium megadoses should not be ingested without a physician`s supervision, they said.
McCarron and Dr. Cynthia D. Morris, of the Oregon Health Sciences University`s division of nephrology and hypertension, showed that they could raise the blood pressure in animals by depriving them of calcium and restore the pressure to normal with increased calcium intake.
Analyses of population studies also revealed that people suffering from hypertension tended to have inadequate calcium consumption in their diets.
In a study of 48 hypertensives given 1,000 milligrams of calcium daily for eight weeks, 44 percent experienced a decline in blood pressures, some to near normal levels, they reported in the December issue of the Annals of Internal Medicine.
Although some doctors regard McCarron`s findings as controversial, others believe it may benefit millions of hypertensives, especially those whose pressure tends to rise with salt consumption.
”Oral calcium supplements can significantly alter blood pressure in . . . hypertensive persons, and may become a valuable nonpharmacologic option in the treatment of hypertension,” said Dr. Lawrence M. Resnick, of the New York Hospital-Cornell University Medical Center, in an accompanying journal editorial.
Calcium`s role in causing muscle cells to contract is complex and little understood, said McCarron. It appears that low calcium levels cause the smooth muscles surrounding blood vessels to contract, he said.
As the vessels become narrower, the blood flowing through is forced to move faster, thereby increasing the pressure, he explained. High blood pressure is a major risk factor for both heart attacks and strokes.
A new class of drugs, called calcium channel blockers, has been developed to treat hypertension. Scientists don`t know exactly how these drugs work but they seem to relax arteries by blocking the entry of calcium into cells. The flow of calcium in and out of cells acts as a trigger for contraction and relaxation.
”I suspect that there are a group of hypertensives who are calcium sensitive,” said Heaney. ”If there isn`t enough calcium in their diets their bodies adjust in a number of different ways and one of the consequences of that is hypertension. These people can have their hypertension prevented or ameliorated with an adequate calcium intake.”
The Oregon findings were bolstered in September at an American Chemical Society meeting by researchers from the Oak Ridge National Laboratory, Oak Ridge, Tenn., who implicated calcium in hard water as the chief protective factor against heart attacks and strokes.
”We feel that the finding is quite important because a person who increases his calcium intake, either by diet, drinking water or calcium supplementation, may be able to prevent heart attacks and strokes,” said Elaine Zeighami, an epidemiologist.
Water is considered ”hard” when it contains calcium and magnesium. The rich life in the seas would not be possible without the heavy calcium content of ocean water and even in freshwater lakes and streams, aquatic life will not flourish unless calcium is present.
While other population studies have shown that people who live in hard-water areas have a lower rate of heart attacks and strokes then people living in soft water areas, the Wisconsin study was the first to pinpoint calcium as the active ingredient.
The study involved nearly 1,400 farmers who drank water from wells on their farms. A careful analysis of the mineral content of the well water revealed that the farmers who had more heart attacks and storkes generally drank soft water, while the healthy farmers drank hard water, said Zeighami.
The role that calcium may play in reducing the risk of colon cancer and possibly other tumors was uncovered by Dr. Martin Lipkin and Harold Newmark of New York`s Memorial Sloan-Kettering Cancer Center, who showed for the first time that abnormally proliferating cancer-prone cells can be restored to normal activity through dietary alterations.
Ten patients who were at high risk for colon cancer were given 1,250 milligrams of calcium daily for two to three months. The abnormal
proliferation of cells lining their colons was reversed and the activity of the cells returned to normal levels, they reported in the Nov. 28, 1985, issue of the New England Journal of Medicine.
Since abnormal cell proliferation is seen in a number of common disorders, such as inflammatory bowel disease, precancerous conditions and cancer, the ability to calm these errant cells may have fundamental implications for a variety of disorders, he said.
As in the case of calcium and high blood pressure, heart attacks and strokes, population studies also show that people who consume more calcium in their diets have a reduced rate of colon cancer.
How calcium works to protect against cancer is not known but it may bind to bile acids and fatty acids in the gut, said Lipkin. These acids are known to irritate tissue and promote abnormal cell proliferation and calcium may neutralize that activity, he explained.
Some researchers, however, speculate that calcium may play a more fundamental role in regulating cell division that has gone haywire.
”I`m rather excited about this whole field of biomodifiers, of which calcium is one,” said Dr. Frank Rauscher, medical director of the American Cancer Society.
”We`ve known for some time that some of the vitamins–C, E and A
–probably have an inhibitory effect against cancer and now here`s something as simple as calcium,” he said.
Research into trace elements and nutrients is intensifying because of the growing realization that they may be harnessed for disease control, said Rauscher.
”What bothers me is that some people will think that they can take a megadose of calcium and ignore the other dietary things that increase the risk of cancer like a high-fat diet and low fiber intake,” he said. ”People are always looking for that cheap pill that will allow them to live with their bad habits.”
How did Americans come to be a calcium deficient population?
One reason is that civilized people have reduced their calorie consumption, and hence their nutrient intake, because they don`t have to work as hard as their early ancestors, said Heaney.
Recent studies of hunter-gatherer tribes in South America and Africa show that they routinely consume about 1,500 milligrams of calcium daily, about three times higher than that consumed by the average middle-aged woman in this country, he said. Most of the calcium in their diet comes from vegetables, roots, tubers and other plants, he said.
Fossil evidence also indicates that early Stone Age humans, the Cro-Magnons, were both taller than we are today and had bigger bones, suggesting that their daily calcium intake was about 1,500 milligrams, said Heaney.
”For the first time in the history of evolution we are trying to adapt to low calcium intakes and we`re not entirely successful,” he said.
Another reason is that calcium is a very underrated mineral, he said. Nutritionists used to think that calcium, except for bones, was insignificant. The chief source of calcium in the modern western diet is milk, they said, and since primitive people did not have milk they couldn`t have had much calcium. It seemed like a clever idea but it was wrong, said Heaney. Hunter-gatherer societies even today, he said, get their calcium from the same place dairy cows do–vegetable sources.
”Doctors used to say that you only needed milk when you were growing and that adults didn`t need it,” he said.
Now it is clear that people need to make an effort to get more calcium from their diet than they have been getting, he said. But even that may not be enough, he said. It may be necessary to fortify various foods with calcium just as iron, vitamins A and D and iodine are routinely added to some foods, he said.
