HEALTH NEWS

Study Title:

Low Salt Diet Causes Cardiovascular Stress

Study Abstract

Background The question of whether reduced sodium intake is effective as a health prophylaxis initiative is unsolved. The purpose was to estimate the effects of low-sodium vs. high-sodium intake on blood pressure (BP), renin, aldosterone, catecholamines, and lipids.

Methods Studies randomizing persons to low-sodium and high-sodium diets evaluating at least one of the above outcome parameters were included. Data were analyzed with Review Manager 5.1.

Results A total of 167 studies were included. The effect of sodium reduction in: (i) Normotensives: Caucasians: systolic BP (SBP) −1.27 mm Hg (95% confidence interval (CI): −1.88, −0.66; P = 0.0001), diastolic BP (DBP) −0.05 mm Hg (95% CI: −0.51, 0.42; P = 0.85). Blacks: SBP −4.02 mm Hg (95% CI: −7.37, −0.68; P = 0.002), DBP −2.01 mm Hg (95% CI: −4.37, 0.35; P = 0.09). Asians: SBP −1.27 mm Hg (95% CI: −3.07, 0.54; P = 0.17), DBP −1.68 mm Hg (95% CI: −3.29, −0.06; P = 0.04). (ii) Hypertensives: Caucasians: SBP −5.48 mm Hg (95% CI: −6.53, −4.43; P < 0.00001), DBP −2.75 mm Hg (95% CI: −3.34, −2.17; P < 0.00001). Blacks: SBP −6.44 mm Hg (95% CI: −8.85, −4.03; P = 0.00001), DBP −2.40 mm Hg (95% CI: −4.68, −0.12; P = 0.04). Asians: SBP −10.21 mm Hg (95% CI: −16.98, −3.44; P = 0.003), DBP −2.60 mm Hg (95% CI: −4.03, −1.16; P = 0.0004). Sodium reduction resulted in significant increases in renin (P < 0.00001), aldosterone (P < 0.00001), noradrenaline (P < 0.00001), adrenaline (P < 0.0002), cholesterol (P < 0.001), and triglyceride (P < 0.0008).

Conclusions Sodium reduction resulted in a significant decrease in BP of 1% (normotensives), 3.5% (hypertensives), and a significant increase in plasma renin, plasma aldosterone, plasma adrenaline, and plasma noradrenaline, a 2.5% increase in cholesterol, and a 7% increase in triglyceride.

This article is based on a Cochrane Review published in the Cochrane Database of Systematic Reviews (CDSR) 2011, Issue 11, DOI: 10.1002/14651858.CD004022.pub3 (see www.thecochranelibrary.com for information). Cochrane Reviews are regularly updated as new evidence emerges and in response to feedback, and the CDSR should be consulted for the most recent version of the review.

From press release:

By Amanda Gardner, HealthDay

Although cutting back on salt does lower blood pressure, new research finds that it may also increase levels of cholesterol, triglycerides and other risk factors for heart disease.

At this point, though, it's not entirely clear what the findings mean for long-term health, according to the study, which appears online Nov. 9 in the American Journal of Hypertension.

"In my opinion, people should generally not worry about their salt intake," said study author Dr. Niels Graudal, senior consultant in internal medicine and rheumatology at Copenhagen University Hospital in Denmark.

For decades, health experts have been saying that reducing sodium consumption lowers the risk for heart disease and stroke. And there's a powerful new government push to reduce salt in prepared and processed foods.

New U.S. dietary guidelines now recommend that people aged 2 and older limit daily sodium intake to less than 2,300 milligrams (mg).

People aged 51 and older, blacks and anyone with high blood pressure, diabetes or chronic kidney disease should consider going down to 1,500 mg per day, many experts say.

And the American Heart Association believes the 1,500-milligram-a-day recommendation should apply to all Americans.

The average American probably consumes 3,400 milligrams of sodium a day which, by these standards, is way too much.

But is it?

One European study recently found that lower sodium excretion was associated with an increased risk of heart-related deaths and higher sodium excretion was not linked with increased risks for blood pressure or complications from heart disease in healthy people.

The study published this week reviewed data from 167 studies that compared high-sodium diets to low-sodium diets.

Less salt did lower blood pressure in whites, blacks and Asians who had either normal blood pressure or high blood pressure.

But this came with significant increases in levels of cholesterol, triglycerides, the enzyme renin (involved in regulating blood pressure) and the hormones noradrenaline and adrenaline (which can affect blood pressure and heart rate).

It's unclear at this point if these changes would translate, over the long run, into more heart attacks or strokes.

But the findings do raise the issue that not all salt consumers are created equal.

"There are those who are more salt-sensitive than others," said Dr. Suzanne Steinbaum, a preventive cardiologist with Lenox Hill Hospital in New York City.

As for the general public, the message is still the same: Less salt is probably better for your health, Steinbaum said.

And even people who do keep their sodium intake within normal bounds should know that might not be enough.

"People need to moderate their lifestyle with better mineral intake, more plant-based foods and more exercise in their daily lives," said Karen Congro, director of the Wellness for Life Program at The Brooklyn Hospital Center in New York City. "Sodium reduction is not going to solve their problems 100 percent."

Study Information

Niels A. Graudal, Thorbjørn Hubeck-Graudal and Gesche Jürgens.
Effects of Low-Sodium Diet vs. High-Sodium Diet on Blood Pressure, Renin, Aldosterone, Catecholamines, Cholesterol, and Triglyceride (Cochrane Review)
American Journal of Hypertension
2011 November
Department of Rheumatology TA4242/Internal Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.