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NUTRITIONALLY SPEAKING

Cut Salt Intake to Prevent Hypertension Later

May 10, 1990|TONI TIPTON

Hypertension experts gathered in Long Beach last week to present research that proves a link between sodium intake and high blood pressure for all Americans, despite claims that the relationship only affects a minority.

Researchers at the Fifth International Interdisciplinary Conference on Hypertension in Blacks explained that hypertension, one of the major risk factors for coronary heart disease, is a "populationwide problem." It is not limited to those who are "salt-sensitive," they said, since all Americans are exposed to the same risk factors for hypertension--smoking, obesity, alcoholism, excessive sodium intake and atherosclerosis.

The current approach to reducing hypertension in the United States, said one of the leading experts, represents "partial and incomplete strategy," since there is no way to test for salt-sensitivity.

Although it was reported that hypertension is more likely to occur in blacks than whites--high blood pressure affects at least 67% of all black men between the ages of 65 and 74 and about 59% of white males the same age--after age 35, at least 80% of the Americans will have a blood pressure that is "above optimal," said Dr. Jeremiah Stamler of Northwestern University in Chicago.

"As seen with cholesterol, high blood pressure is a multifactorial problem, not just a black or white problem. It is a population-wide problem.

"If the strategy remains the same and we wait for people to show the clinical signs of hypertension, we are guilty of neglect and (exposing people to) excess risk (for complications of hypertension)," Stamler said.

Normal blood pressure is 120/80 millimeters of mercury (mm Hg). This figure represents the force of blood as it pushes against the arteries when the heart pumps. It is a ratio of systolic over diastolic.

Other than age and race, there are few confirmed causes for high blood pressure, which is measured at 140/90 mm Hg. Other risk factors are merely suspected.

Instead of accepting that blood pressure will rise with age, Stamler hopes that intervention at an early age could eliminate the "abnormal" climb in blood pressure, he said. The age-induced increase, he said, is a direct result of a lifestyle and it is aggravated by a high sodium intake.

"The 'normal' is for blood pressure to rise with age, but this rise is abnormal," said Stamler. "It is complicated by the American lifestyle. Smoking and high blood pressure are among the risk factors for heart disease, but high blood pressure is pivotal--it aggravates the other risks. . . . With blood pressure, salt is the pivotal one (risk factor)."

The average American consumer gets about 10% of his daily sodium intake from the natural salt that occurs in food. About 15% can be attributed to the addition of salt during cooking and at the table. The overwhelming majority is derived from salt added during processing and manufacturing of food--about 75%.

Stamler said, if Americans in general, would cut back on the amount of processed food they eat, it could potentially reduce the occurance of hypertension in the nation. And he cited recommendations from the National Research Council's extensive "Diet and Health Report" and from the American Heart Assn. as support. They recommend that consumers reduce sodium intake from the current level of consumption to a "safe and adequate" level of 1,100 to 3,300 milligrams daily. (One teaspoon contains 2,000 mg sodium.)

Americans have a "clear opportunity" to change their life expectancy, Stamler said. By making changes in food selection, it could add three and a half years to the average life span--especially for blacks who live six to seven years fewer than whites, according to government statistics.

But there has been some controversy about this advice. Opponents believe that there are other risk factors that are more important than sodium intake. They are body weight and alcohol consumption.

The question was raised after interpretation of the population study Intersalt, which surveyed and studied 24-hour urine samples of more than 10,000 men and women in 32 countries. Intersalt found that sodium intake has a role in raising risk for hypertension. It also showed that in some groups body weight and alcohol use can be greater predictors of blood pressure status than sodium intake.

But Stamler emphasized the salt component is the most influential. He said that the data clearly indicates that eating less salt was of benefit: In all populations, the higher the sodium intake, the greater the increase in blood pressure with age.

From this, he and his colleagues concluded that a lifetime of reduced salt intake, coupled with weight maintenance and conservative alcohol consumption, could lessen a person's chances of developing high blood pressure in old age.

"What we learned from Intersalt," said Dr. Clarence E. Grim, of the Charles Drew Medical Center, Los Angeles, "is that in societies that eat very little salt, there is very little hypertension. Salt is the most critical indicator in blood pressure. We are currently eating 150 times what what we need."

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