A low-salt diet of just one week can markedly lower blood pressure

A week is all it takes to notice the effects of making the switch to a low-salt diet, and the health benefits are substantial.

A US study published in the Journal of the American Medical Association on November 11 found that after a week of switching from a high- to a low-sodium diet, 75% of participants had a median drop in systolic blood pressure of 8 mmHg (millimeters of mercury).

Senior cardiologist Associate Professor Chin Chee Tang of the National Heart Centre Singapore stated that although an 8 mmHg drop may not seem significant, it is clinically significant and lowers the risk of stroke, heart attack, and kidney failure.

The National University Heart Centre in Singapore’s Professor Tan Huay Cheem, a senior cardiologist, stated: “Do not underestimate this reduction in systolic blood pressure, as a 5mmHg reduction can reduce the risk of major cardiovascular events by about 10%.” When applied to the broader population, the impact on health is enormous.

A systolic reading of 120 mm Hg over an 80 mm Hg diastolic reading, or 120/80, is considered to be good blood pressure. A normal blood pressure in Singapore is less than 130/85. The pressure in the arteries during a heartbeat is measured by the diastolic reading, which also records the pressure during the heart’s rest period.

Over time, hypertension can weaken the heart and lead to heart failure. Additionally, it raises the risk of renal failure and stroke.

213 participants between the ages of 50 and 75 who had normal blood pressure (25%) controlled hypertension (20%) uncontrolled hypertension (31%), and untreated hypertension (25%), were included in the study.

For one week, they were given 2,200 mg of sodium daily as part of a high-sodium diet. After that, they were given 500 mg of sodium daily for a week. The World Health Organization advises against consuming more than 2,000 mg of sodium per day, which is equivalent to about 5 grams of salt, or less than a teaspoon.

Prof Tan said: “This study is important in that it showed conclusively the beneficial impact of salt reduction on blood pressure. This benefit extends not only to hypertensive patients but also normal individuals.”

Currently, there are over 700,000 diabetics in Singapore. By 2050, the figure is expected to exceed one million.

Nearly three out of four diabetics experience high blood pressure, according to Prof. Tan.

“On top of that, you don’t have to wait long before the beneficial effects are demonstrated, as the lower blood pressure is observed within a week of salt reduction,” he said.

Professor Chin expressed his support for the study, stating that it was well-designed and carried out.

Despite the small number of participants—just over 200—everyone was given access to diets high and low in sodium, eliminating the possibility of individual differences. More accurate readings were obtained with the use of ambulatory blood pressure monitoring, which measures blood pressure continuously throughout the day, even while a person is sleeping.

Urinary testing was also used in the study to assess salt intake compliance. This revealed that, despite being on a low-sodium diet where they were only allowed to take 500 mg of sodium daily, the participants were actually taking about 1,300 mg.

Prof Chin said: “Reducing salt intake is challenging as it affects the taste profile. It may not be realistic or practical to expect an individual to be completely compliant with a 500mg sodium intake restriction.”

However, the results of the study indicated that “there were blood pressure benefits” even when the subjects consumed 1,300 mg of sodium daily as opposed to 500 mg.

“This, therefore, is encouraging to me. It may not be realistic to expect everyone to be completely compliant with such a low-salt diet, but the concept is to increase awareness that the lower the salt content in the diet, the better the blood pressure benefits,” he said.

Prof. Chin stated that the impact on blood pressure occurred within a few days, which emphasizes the importance of understanding how diet affects daily bodily functions.

He added that the fact that the blood pressure drop happened to both individuals who are known to be hypertensive and those who do not typically have high blood pressure, regardless of whether they are taking medication, is another significant finding.

Said Prof Chin: “This implies that salt restriction is still necessary among hypertensive patients who are on medication.”

He added: “Given the high intake of salt in Singapore and other Asian societies, this is an opportunity to address one of the important modifiable risk factors for cardiovascular disease – high blood pressure.”

For those who cook their own food, he said, a drop in blood pressure is not too difficult to achieve because following a low-salt diet is equivalent to cutting back on one-half teaspoon of “usual” salt intake.

However, Prof. Chin acknowledged that packaged and processed foods, as well as food prepared by outside sources like restaurants, present greater challenges.