Calcium Lowers Blood Pressure in Half of Patients Study Group

University of Oregon researchers, who have argued that a diet deficient in calcium may be more important than an excess of table salt in contributing to high blood pressure, have now shown that calcium pills can be used to treat some patients with the disease.

Dr. David A. McCarron said some of the hypertensive patients studied did not respond to calcium, but about half had “quite substantial” drops in their blood pressure. The article and two editorials about the findings were published today in the December issue of the Annals of Internal Medicine.

McCarron’s findings are controversial.

“I am not a believer that a majority of patients with hypertension have a calcium deficiency,” said another leading researcher, Dr. Norman Kaplan of the University of Texas Medical Center in Dallas.

Kaplan said a study he will present at a scientific meeting in New Orleans in February had failed to confirm McCarron’s findings. He said a rational approach is to consider calcium treatment for hypertension only in patients with another medical reason to take the pills.

The Oregon study contributes to a continuing debate among medical researchers and public health experts about the relationship of blood pressure to the consumption of various nutrients, such as table salt (sodium); potassium, often used as a salt substitute, and calcium.

The debate is important because of the 30 million to 40 million adults with hypertension, 80% have mild forms that may be treatable without drugs. Numerous therapies have been advocated, including weight loss, salt reduction, exercise and relaxation techniques.

While McCarron, a physician, said the overall effect of the calcium was small, it was “consistent” with the amount of blood pressure reduction from sodium restriction and “at least” as good as that seen with potassium supplements.

“It may look small, but the change is actually potentially quite large across the entire hypertensive population,” he said.

Calcium is ubiquitous in the diet, primarily through dairy products and in some antacids for stomach upset. It is available in pill form without a prescription.

Millions of people take calcium for a variety of conditions, primarily older white women who are susceptible to a thinning of the bones called osteoporosis.

Last year, in a report published in the journal, Science, McCarron challenged the conventional wisdom that too much salt was the culprit in hypertension. Instead, his research team argued that a low consumption of calcium and, to a lesser extent, potassium, were most important for high blood pressure.

In his latest study, McCarron and colleague Cynthia D. Morris treated 48 people with mild to moderate high blood pressure and 36 with normal blood pressure. Each received either 1,000 milligrams of calcium a day or placebo pills during the eight-week study periods. The recommended dietary consumption of calcium is 800 milligrams a day, according to the National Academy of Sciences.

In total, 44% of patients with high blood pressure had a “beneficial response” to calcium, as contrasted with the placebo, and blood pressure fell to the normal range in 13%. While 19% of the patients with normal blood pressure responded to calcium, as a group their blood pressure was unchanged.

A “beneficial response” was defined as a 10-mm Hg (millimeters of mercury) decrease in systolic blood pressure with calcium, as contrasted with the placebo. Systolic blood pressure is the peak pressure achieved in the circulation, when the heart pumps blood to the body.

Infrequent but similar side effects were seen when patients were given calcium or placebo. The side effects did not require any patients to drop out of the study.

McCarron said studies are in progress to determine whether increasing calcium in the diet can lower blood pressure and to assess long-term use of the tablets.