Prof Deepak Gupta, co-principal investigator, of Vanderbilt, said: “In the study, middle-aged to elderly participants reduced their salt intake by about one teaspoon a day compared with their usual diet.
“The result was a decline in systolic blood pressure by about six millimetres of mercury, which is comparable to the effect produced by a commonly utilised first-line medication for high blood pressure.”
Prof Norrina Allen, co-principal investigator, of Northwestern University Feinberg School of Medicine, said: “We found that 70 to 75 per cent of all people, regardless of whether they are already on blood pressure medications or not, are likely to see a reduction in their blood pressure if they lower the sodium in their diet.”
The study is one of the largest to investigate the effect of reducing salt in the diet on blood pressure to include people with high blood pressure, also known as hypertension, and already on medications.
Prof Allen said: “We previously didn’t know if people already on blood pressure medication could actually lower their blood pressure more by reducing their sodium.”
She said the total daily sodium intake recommended by the American Heart Association (AHA) is less than1,500 milligrams, and the study was designed to decrease it even lower than that.
‘Reducing your sodium in any amount will be beneficial’
“It can be challenging, but reducing your sodium in any amount will be beneficial,” Prof Allen added
“High blood pressure can lead to heart failure, heart attacks, and strokes because it puts extra pressure on your arteries.
“It affects the heart’s ability to work effectively and pump blood.”
People aged in their 50s, 60s and 70s from Birmingham, Alabama, and Chicago were put on either a high-sodium diet (2,200 mg per day on top of their usual diet) or low-sodium diet (500 mg in total per day) for a week, after which they crossed over to the opposite diet for a week.
On the day before each study visit, participants wore blood pressure monitors and collected their urine for 24 hours.
Among the 213 participants, systolic blood pressure was “significantly lowered” by seven to eight mm/Hg when they were on the low-sodium diet compared with the high-sodium diet, and by six mm/Hg compared with their usual diet.
Overall, 72 per cent of the participants experienced a lowering of their systolic blood pressure on the low-sodium diet compared with their usual diet.
‘Any physical activity is better than none for most people’
Prof Gupta added: “The effect of reduction in dietary sodium on blood pressure lowering was consistent across nearly all individuals, including those with normal blood pressure, high blood pressure, treated blood pressure and untreated blood pressure.
“Just as any physical activity is better than none for most people, any sodium reduction from the current usual diet is likely better than none for most people with regards to blood pressure.”
The blood pressure lowering effect of dietary salt reduction was achieved rapidly and safely within one week, according to the research team.
Prof Cora Lewis, co-investigator of Alabama, said: “The fact that blood pressure dropped so significantly in just one week and was well tolerated is important and emphasises the potential public health impact of dietary sodium reduction in the population, given that high blood pressure is such a huge health issue worldwide.”
“It is particularly exciting that the products we used in the low-sodium diet are generally available, so people have a real shot at improving their health by modifying their diet in this way.”
The findings, due to be published in the Journal of the American Medical Association, were presented at the annual American Heart Association Scientific Sessions in Philadelphia.
