Hidden salt in tap water may affect blood pressure — Experts

Experts, in a global analysis, have suggested that drinking water itself could be an overlooked source of salt and one that may quietly raise blood pressure for millions of people worldwide.

Published in BMJ Global Health, the study found that higher salt content in drinking water was associated with higher blood pressure and a greater risk of hypertension, especially among people living in coastal regions.

The study was led by Florida International University researchers in collaboration with investigators from Johns Hopkins University, Vanderbilt University, and the Pan American Health Organisation.

The researchers conducted a systematic review and meta-analysis of data from 27 population studies involving more than 74,000 participants across the United States, Bangladesh, Vietnam, Kenya, Australia, Israel, and several European countries.

They found that people exposed to higher salt concentrations in their drinking water had, on average, higher systolic and diastolic blood pressure than those exposed to lower salt concentrations in their drinking water. Specifically, systolic blood pressure was approximately 3.2 mm Hg higher, whereas diastolic blood pressure was nearly 2.8 mm Hg higher.

Higher salt content in drinking water was also associated with a 26% increased risk of hypertension, with the strongest and most consistent associations observed in coastal populations.

Senior researcher Rajiv Chowdhury, chair of global health at Florida International University in Miami, declared that there may be modest increases at the individual level, but when large populations are exposed, even small shifts in blood pressure can have significant public health effects.

According to him, “To put it in perspective, the risk level observed in this study for water salinity is like other established cardiovascular risk factors, such as low physical activity, which increases hypertension risk by approximately 15 to 25%.”

Salt can enter drinking water in many ways. Still, along coastlines, it most commonly occurs by saltwater intrusion into groundwater systems, which make up nearly half of the world’s drinking water supply.

While dietary sodium intake has long been recognised as a risk factor for high blood pressure, salt from drinking water, especially for those living in coastal areas, is not currently considered in most hypertension prevention guidelines.

While the analysis found consistent links between high salt content in drinking water, elevated blood pressure, and hypertension risk, the researchers found insufficient evidence to conclude other cardiovascular outcomes, such as heart attack or stroke.

“This is a major unmet scientific area, and our meta-analysis should inform future studies that will include wider chronic disease outcomes,” Chowdhury said.

These findings raise important questions for public health planning, particularly in coastal areas where drinking water salinity is expected to be higher.

Monitoring water quality, improving water management strategies, and considering environmental factors in hypertension prevention efforts may help reduce long-term cardiovascular risk.

Taken together, these findings underscore the importance of looking beyond individual behaviours when addressing the risk of high blood pressure. By highlighting drinking water salinity as a potential contributor, this study points to water quality as a factor that intersects with both public health and long-term planning in coastal regions.