Big BP Reductions When DASH Diet Combined With Low Sodium Intake

ANAHEIM, CA—Combining a diet rich in fruit, vegetables, low-fat dairy, and reduced saturated and total fat with lowered sodium intake is associated with progressively larger reductions in systolic blood pressure among patients considered prehypertensive and those with stage 1 hypertension, new research shows.

In the study, the largest reductions were observed among individuals with baseline blood pressure levels 150 mm Hg or greater who were randomized to the Dietary Approaches to Stop Hypertension (DASH) diet in combination with reduced sodium intake as compared with a typical American diet high in sodium.

The findings, which were presented today at the American Heart Association 2017 Scientific Sessions and published simultaneously in the Journal of the American College of Cardiology, have both clinical and public health implications, according to the researchers.

“It’s an important question,” lead investigator Stephen Juraschek, MD (Beth Israel Deaconess Medical Center, Boston, MA), told TCTMD, “A lot of times we look at diet as something that’s important for primary prevention, predominantly something that can give us a modest [blood pressure-lowering] effect. Sometimes we think, in the people with really bad uncontrolled hypertension, ‘I need to just start with medication right away or only medication can achieve what this person needs.’”

Instead, the findings suggest that individuals with uncontrolled hypertension, particularly those with levels between 140 and 159 mm Hg, who represent the majority of patients with hypertension, can experience substantial reductions in systolic blood pressure with dietary changes.

The study, known as the DASH-Sodium trial, included 412 participants with a baseline systolic blood pressure ranging from 120 to 159 mm Hg (averaged across three screening visits). The study was designed to compare the effects of three different daily sodium intakes—1,150 mg (low), 2,300 mg (medium), and 3,450 mg (high)—in the context of eating the DASH diet or a typical American diet.  

All meals and snacks were provided to participants and they ate their main meal—either lunch or dinner—at one of the study centers under observation. Participants ate a high-sodium/control diet during a 2-week run phase and were then randomized to either the DASH or control diet. On the assigned diet, participants consumed either low, medium, or high sodium levels for 30 days (the intervention periods were followed by a 5-day washout period).

Diet Matters

For participants assigned to the control diet, reducing sodium intake from high to low levels significantly reduced systolic blood pressure regardless of baseline blood pressure. For those with a baseline systolic blood pressure ≥ 150 mm Hg, low sodium intake while on the control diet reduced systolic blood pressure 7.04 mm Hg compared with high sodium intake. For those assigned to the DASH diet, reducing sodium intake from high to low levels also reduced systolic blood pressure in all participants, with the biggest reduction, 10.41 mm Hg, observed in those with baseline systolic blood pressure ≥ 150 mm Hg.

Even when individuals were consuming high amounts of sodium—3,450 mg is what the average American typically consumes—adhering to the DASH diet reduced systolic blood pressure compared with the control diet. Blood pressure reductions were observed in all individuals, and largest in those with the highest baseline systolic blood pressure, but there was no significant trend across the different strata of baseline levels (< 130 mm Hg, 130-130 mm Hg, 140-149 mm Hg, and ≥ 150 mm Hg).

Finally, a combination of low sodium intake and the DASH diet reduced blood pressure when compared with a high sodium/control diet in all participants regardless of baseline blood pressure. The reduction ranged from 5.30 mm Hg in individuals with a baseline systolic blood pressure < 130 mm Hg to 20.79 mm Hg in those with stage 1 hypertension.

Regarding the reduction of 20.79 mm Hg, Juraschek said it was “massive” and not something they had expected. He noted that among patients with systolic blood pressure of 140-149 mm Hg after the dietary run-in period, just 18% had hypertension after eating the low sodium/DASH diet for 4 weeks. For those with systolic blood pressure ≥ 150 mm Hg after the run-in period, just 25% had hypertension after the low sodium/DASH diet.

“If these patients were in my clinic before the study, I’d think, ‘Wow, you’re at 150 [mm Hg] and SPRINT says we have to get super low, I need to start getting aggressive with medication.’ But what we’re seeing is that after just 4 weeks of a low sodium healthy diet, three-quarters of those folks had their hypertension resolved,” he said.

To put the results in context, Juraschek told TCTMD that ACE inhibitors reduce systolic blood pressure by 12 mm Hg compared with placebo, while beta-blockers and calcium channel blockers lower blood pressure by 13 mm Hg and 16 mm Hg, respectively. Additionally, the US Food and Drug Administration requires any new antihypertensive medication to lower systolic blood pressure by just 3-4 mm Hg.

“We’re seeing effects on par with what’s been established with known drugs in the field,” said Juraschek, referring to the combination of the low sodium/DASH diet. “I’m not against medication by any means, and they certainly have a very important role in achieving control of blood pressure which is critical for long-term health, but the results suggest that if diet is taken seriously by physicians and patients it can really have a pronounced impact.”    

The researchers say further studies are needed, particularly to determine the magnitude of benefit of the DASH diet and low sodium intake among individuals with more severe hypertension, such as those with systolic blood pressure ≥ 160 mm Hg.

Juraschek said that the DASH diet tends to be easier to adopt than adhering to 1,150 mg of sodium daily. This is even more pronounced when individuals eat out, particularly when the amount of sodium in food is not listed. “It’s really challenging, even for those trying to reduce their sodium, to make educated decisions about their intake,” he said.