Salt may be culprit for uncontrolled blood pressure

People with high blood pressure that isn't controlled by multiple medications are likely eating too much salt, new findings in the journal Hypertension show.

Individuals with so-called resistant hypertension showed sharp reductions in their blood pressure when they dramatically cut their salt intake, Dr. Eduardo Pimenta of the University of Queensland School of Medicine in Brisbane, Australia and his colleagues found.

"It was an amazingly large reduction in blood pressure," Dr. Lawrence J. Appel of Johns Hopkins University in Baltimore, who wrote an editorial accompanying the study, told Reuters Health. Appel estimated that 10% to 20% of people have resistant hypertension, meaning they are taking three or more blood pressure medications but their blood pressure is still too high.

But the reductions in sodium intake in Pimenta's study-down to 1.15 grams per day-would be very tough for people to achieve in a real-world setting, Appel added. (Sodium levels in food are correlated with salt levels.) "You can advise people to reduce sodium but the food supply has so much sodium it's very difficult for individuals to do this on their own."

Pimenta and his team had 12 people with resistant hypertension alternate between low and high sodium diets for a week each, with a two-week "washout" period between the diets.

Study participants' initial average systolic blood pressure, the top number in a blood pressure reading, was 145.8 millimeters of mercury (mm Hg), while diastolic pressure, the lower reading, was 83.9 mm Hg. They were taking an average of 3.4 antihypertensive medications each.

On the high sodium diet, they were consuming 5.7 grams of sodium daily, while the low-sodium diet contained 1.15 grams of sodium daily.

US and UK guidelines recommend people consume less than 6 grams of sodium daily, while the World Health Organization recommends reducing intake even further, to less than 5 grams. But people in the developed world typically consume 9 to 12 grams of sodium a day.

In the study by Pimenta and his team, going on the low-salt diet reduced people's systolic blood pressure by 22.7 mm Hg, on average, and their diastolic pressure by 9.1 mm Hg.

"The current results suggest that patients with resistant hypertension are exquisitely salt-sensitive," the researchers suggest. These individuals' salt intake is probably causing them to retain so much fluid that standard...treatments for reducing blood pressure aren't helping them, they add.

In the other study, Dr. Feng J. He of the University of London and her colleagues tested a less dramatic sodium reduction in 71 whites, 69 blacks, and 29 Asians. All spent two weeks on a low-sodium diet, and were then randomly assigned to take sodium pills or a placebo for six weeks, after which they were switched to the opposite treatment for another six weeks.