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Why Salt Makes Blood Pressure Rise: New Study


People are often told that too much salt in their diet may make their blood pressure rise, but why salt cause this response has been unclear. Now researchers from Case Western Reserve University School of Medicine and Kent State University say they have uncovered an answer.

Are you salt sensitive?

The cardiovascular system is responsible for several vital functions, two of which are maintaining normal blood pressure and playing a role in controlling body temperature. A research team led by Robert P. Blankfield, MD, MS, clinical professor of family medicine at Case Western Reserve University School of Medicine, and Ellen L. Glickman, PhD, professor of exercise science at Kent State University, set out to determine whether these two functions might be involved in how salt consumption impacts blood pressure.

The Centers for Disease Control and Prevention notes that about one-third of adults in the United States have high blood pressure (hypertension). People who are salt sensitive, which means salt intake tends to increase their blood pressure, causes their blood vessels to stiffen, or both, are believed to make up about 10 to 20 percent of the population.

Identifying who is salt sensitive, however, requires some patience. The most effective way is for someone who has hypertension to try a salt-restricted diet and monitor its effect on their blood pressure.

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In the new study, the investigators monitored the effect of water and salt consumption versus just water in 22 healthy men who did not have hypertension. All the participants had their blood pressure, rectal temperature, cardiac index (how much blood the heart pumped per minute), and urine output documented at one, two, and three hours after they ingested the salt and water or the water alone.

Results of the evaluation showed that participants who ingested salt and water had a lower body temperature than those who ingested water alone. Body temperature also declined more in participants who were not sensitive to salt than in those who were salt sensitive.

The 2010 Dietary Guidelines for Americans recommend limiting intake of sodium to less than 2,300 milligrams daily for adults, but to 1,500 mg for people who are older than 51, black, or who have diabetes, high blood pressure, or chronic kidney disease.

Blankfield noted that “it appears that salt sensitive individuals maintain core body temperature equilibrium more effectively than salt resistant individuals, but experience increased blood pressure in the process,” while individuals who are salt resistant can maintain blood pressure equilibrium better than people who are salt sensitive.

These findings show that the cardiovascular system in salt sensitive individuals finds it difficult to simultaneously multitask regulation of body temperature and blood pressure. This discovery may further the development of a way to effectively prevent and treat high blood pressure in individuals who are salt sensitive.

Case Western Reserve University