Too much salt can damage blood vessels and lead to hypertension

By Laura Cowen

A high sodium intake over a prolonged period of time is associated with increased vascular dysfunction, which may lead to hypertension, researchers report.

Results of the PREVEND (Prevention of REnal and Vascular End stage Disease) study showed that individuals with the highest sodium intake over a median follow-up period of 6.4 years had the greatest increases in two markers of endothelial dysfunction, namely serum uric acid (SUA) and urine albumin excretion (UAE), during the same period.

In addition, a higher sodium intake was associated with an increased risk for hypertension, with the greatest increases observed among those with the highest levels of SUA and UAE.

The findings "add to the considerable evidence that a diet heavy on salt is closely linked to high blood pressure," said lead author of the study John Forman (Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA) in a press statement.

The researchers prospectively analyzed the associations between sodium intake and the change in SUA (n=4062) and UAE (n=4146) among PREVEND participants who were not taking antihypertensive medications. They also examined the association of sodium intake with the incidence of hypertension (n=5556) among non-hypertensive participants.

Sodium intake was assessed by collecting multiple 24-hour urine samples.

During the follow-up period, there were 878 cases of hypertension. Incidence was higher among patients in the highest quartile of sodium intake (median 271 mmol/day) compared with the lowest quartile (97 mmol/day), at 99 vs 28 cases per 100,000 person years), which is equivalent to a significant 21% increased risk.

In addition, each 1 gram increase in sodium intake (equivalent to 2.5 g of table salt) was associated with a significant 1.2 µmol/L greater increase in SUA and a significant 4.6 mg/day greater increase in UAE over time.

Further analysis showed that the association between sodium intake and hypertension was modified by both SUA and UAE. Specifically, individuals who had the highest SUA levels and greatest sodium intake were 32% more likely to develop hypertension than those with the lowest levels of each. Similarly, participants with the highest UAE levels and greatest salt intake were 86% more likely to develop hypertension than those with the lowest levels.

Writing in Circulation, Forman and co-authors conclude that a "High sodium diet over the long term may lead to endothelial dysfunction and vascular damage, generating a biological state in which continuance of the high sodium diet may produce hypertension (a sodium amplification loop)."

"This study reinforces guidelines backed by the American Heart Association and other professional organizations that recommend reducing salt consumption to minimize the risk of developing high blood pressure," Forman said.

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