Sodium is usually discussed in the context of food, but new research suggests that drinking water may also contribute to blood pressure levels in some parts of the world.
A study published in BMJ Global Health found that higher salinity in drinking water was associated with higher blood pressure and a greater risk of hypertension. The association was strongest in coastal areas, where saltwater intrusion into groundwater is more common.
Researchers analyzed data from 27 population-based studies involving more than 74,000 participants across multiple countries, including the United States, Bangladesh, Vietnam, Kenya, Australia, Israel and several European nations. Across these studies, people exposed to higher levels of sodium in drinking water had higher average blood pressure than those exposed to lower levels.
On average, systolic blood pressure was about 3.2 mm Hg higher and diastolic blood pressure nearly 2.8 mm Hg higher among those exposed to higher water salinity. Higher salinity was also associated with a 26% increased risk of hypertension. While these differences are modest at the individual level, the authors note that even small shifts in blood pressure can have meaningful public health implications when large populations are affected.
Salt can enter drinking water through several pathways, most notably saltwater intrusion into groundwater supplies. This issue is particularly relevant in coastal regions, where freshwater and saltwater systems sit close together underground. Globally, more than 3 billion people live in coastal or near-coastal areas, many of which rely on groundwater as a primary source of drinking water.
Food remains the dominant source of sodium intake for most people, and the study does not suggest that drinking water replaces dietary sodium as the primary concern. However, in areas where water salinity is elevated, sodium from drinking water may add to overall exposure, particularly for individuals who already need to manage blood pressure.
The researchers emphasize that environmental exposures, such as water quality, are often overlooked in discussions of hypertension risk, which tend to focus on individual behaviors alone. The findings highlight the importance of considering broader environmental factors alongside diet and lifestyle when addressing population-level cardiovascular health.
The analysis was observational and cannot establish cause and effect. The studies included varied in how water salinity and blood pressure were measured, and the authors note that more research is needed to understand how changes in water quality over time may influence long-term cardiovascular risk.
The authors reported no specific grant funding for this research from public, commercial or not-for-profit sources.