For most people, salt is something they think about when cooking or eating, not when turning on the tap.
But new research suggests that drinking water itself may be an unexpected source of salt and that this hidden salt could quietly raise blood pressure for millions of people around the world.
The study, published in BMJ Global Health, shows that people who drink water with higher salt levels tend to have higher blood pressure and a greater risk of developing hypertension, especially those who live near the coast.
High blood pressure is one of the leading causes of heart disease and stroke. It often develops slowly and without clear symptoms, which is why it is sometimes called a “silent killer.” For many years, doctors and public health experts have focused on diet, exercise, stress, and smoking as the main causes of high blood pressure.
Salt intake from food has been especially important, because eating too much salt is known to raise blood pressure. However, this new research suggests that salt in drinking water may also play a role and has been largely overlooked.
The study was led by researchers from Florida International University, together with experts from Johns Hopkins University, Vanderbilt University, and the Pan American Health Organization.
The research team reviewed and combined data from 27 large population studies carried out in different parts of the world, including the United States, Bangladesh, Vietnam, Kenya, Australia, Israel, and several European countries. Altogether, the analysis included more than 74,000 people.
When the researchers compared people exposed to saltier drinking water with those drinking water that had lower salt levels, they found clear differences in blood pressure. On average, people drinking saltier water had higher readings for both the top number and the bottom number of blood pressure.
The top number, which measures pressure when the heart beats, was about 3.2 points higher. The bottom number, which measures pressure when the heart rests between beats, was nearly 2.8 points higher.
At first glance, these increases may seem small. But across large populations, even small rises in blood pressure can lead to many more cases of heart disease and stroke.
The researchers also found that people exposed to higher water salinity had a 26 percent higher risk of developing high blood pressure. This risk increase is similar to other well-known risk factors, such as not getting enough physical activity.
The strongest links were seen in coastal areas. This is not surprising, because salt can enter drinking water more easily in these regions. One major reason is saltwater intrusion, which happens when seawater moves into underground freshwater sources.
Groundwater provides drinking water for nearly half of the world’s population. In coastal regions, freshwater and saltwater often sit close together underground, making it easier for salt to seep into wells, especially as sea levels rise and water demand increases.
More than three billion people around the world live in coastal or near-coastal areas. In many of these places, groundwater is the main source of drinking water. This makes water salinity an important issue not just for taste, but for long-term health.
Yet current health guidelines for preventing high blood pressure rarely consider salt from drinking water. They mainly focus on salt from food.
The researchers stress that this study is not meant to cause panic. Food remains the largest source of salt for most people. But in areas where drinking water is saltier, water can add to the total salt intake without people realizing it. This extra salt may be especially important for people who already have high blood pressure or are at risk of developing it.
The study did not find enough evidence to clearly link salty drinking water to other heart problems such as heart attacks or strokes. This does not mean there is no connection, but rather that more research is needed. The authors say future studies should look more closely at long-term health outcomes related to water quality.
From a public health point of view, the findings suggest that environmental factors deserve more attention. High blood pressure is not caused only by personal choices.
Where people live and the quality of their water may also affect their health. In coastal regions, monitoring water salinity, protecting groundwater, and improving water management could help lower health risks over time.
This research also highlights the importance of planning for the future. Climate change, rising sea levels, and growing populations may increase saltwater intrusion in many parts of the world. Protecting freshwater sources is not just an environmental issue, but a health issue as well.
In reviewing and analyzing the findings, this study provides strong evidence that salt in drinking water is linked to higher blood pressure and a greater risk of hypertension, particularly in coastal populations. While the increase in risk for individuals is modest, the potential impact on large populations is significant.
The results support the idea that managing high blood pressure requires looking beyond diet and lifestyle alone. Environmental factors like water quality should be included in prevention strategies, especially in vulnerable regions.
Future research will be essential to understand long-term heart risks and to guide policies that protect both water resources and public health.
If you care about high blood pressure, please read studies that early time-restricted eating could help improve blood pressure, and natural coconut sugar could help reduce blood pressure and artery stiffness.
For more information about blood pressure, please see recent studies about How to eat your way to healthy blood pressure and results showing that Modified traditional Chinese cuisine can lower blood pressure.
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