At the time of the study, according to the National Health and Nutrition Examination Survey, Americans consumed about 150 mmol/day of sodium, which is considered by the FDA to be harmful and may increase a person’s risk for high blood pressure, heart disease and stroke.
Participants were sorted into four groups based on their baseline systolic blood pressure: 120-129, 130-139, 140-149 and 150 or greater baseline systolic blood pressure.
After four weeks, the investigators found that the group with 150 or greater baseline systolic blood pressure on just the DASH diet had an average of 11 mm Hg reduction in systolic blood pressure compared to a 4 mm Hg reduction in those solely on the DASH diet, but whose baseline systolic pressures were less than 130.
When the researchers combined the DASH diet with the low-sodium diet and compared participants’ blood pressures to those on the high-sodium control diet, they found that the group with less than 130 systolic blood pressure at baseline had a 5 mm Hg reduction in systolic blood pressure; the group with 130-139 mm Hg baseline systolic blood pressure had a 7 mm Hg reduction; and the group with baseline systolic blood pressure between 140-149 had a 10 mm Hg reduction.
Most surprisingly, say the researchers, a participant who had a baseline systolic blood pressure of 150 or greater and was consuming the combination low-sodium/DASH diet had an average reduction of 21 mm Hg in systolic blood pressure compared to the high-sodium control diet.
“This is outstanding, it’s huge,” says Juraschek, because it suggests that those at highest risk for serious hypertension achieve the greatest benefit from the combination diet.
To put the potential impact of the findings into context, Juraschek says, the FDA requires any new antihypertensive agent submitted for approval to lower systolic blood pressure by 3-4 mm Hg. Most established medications on the market, such as ACE inhibitors, beta-blockers, or calcium channel blockers, on average reduce systolic blood pressure by 10-15 mm Hg.
“What we’re observing from the combined dietary intervention is a reduction in systolic blood pressure as high as, if not greater than, that achieved with prescription drugs,” says senior study author Lawrence Appel, M.D., M.P.H., professor of medicine at the Johns Hopkins University School of Medicine. “It’s an important message to patients that they can get a lot of mileage out of adhering to a healthy and low-sodium diet.”
The researchers caution that the study did not address effects in people with systolic blood pressure of 160 or greater or in persons with prior cardiovascular disease or medication treated diabetes. Further studies with larger sample sizes are needed to investigate the impact of the low-sodium/DASH diet on these populations.