Not Just Thirst

What if drinking more water could help prevent heart disease?

That’s the compelling question driving a major new study led by Prof. Jonathan Rabinowitz of Bar-Ilan University’s Wellness Lab and Natalia I. Dmitrieva of the Laboratory of Cardiovascular Regenerative Medicine at NIH, in collaboration with Leumit Health Services. Drawing from over 20 years of electronic health records covering 407,000 healthy Israeli adults, the researchers uncovered a striking link between hydration levels and long-term cardiovascular health.

The findings suggest that even when serum sodium levels-a measure of hydration- fall within the so-called “normal” range, values of 140 mmol/L or higher are associated with a significantly increased risk of developing both hypertension and heart failure. In fact, the risk of hypertension rose by 13% to 29% as sodium levels increased, while the risk of heart failure climbed by up to 20%.

A new lens on preventive care

This study transforms a routine blood test into a powerful early warning tool. Because serum sodium is tested so frequently and universally, it could become an accessible way to identify people at risk—before they show symptoms. Prof. Rabinowitz explains it simply: “Hydration isn’t just about feeling refreshed. It might be a powerful, modifiable tool to protect against some of the most prevalent chronic diseases of our time.”

The data also shows just how widespread the issue may be. Among current, generally healthy members of Leumit Health Services, nearly two-thirds have serum sodium levels in the 140-146 mmol/L range—suggesting  that most health adults are potentially at increased risk, without even knowing it.

Why this study stands out

The strength of this research lies in both its scale and its design. It draws on one of the most comprehensive healthcare databases in Israel, while specifically excluding individuals with existing chronic conditions to focus purely on hydration as a factor. It also includes a wide age range—from 18 to over 100—and tracks health outcomes for up to two decades.

These parameters allowed the researchers to detect risk thresholds long before clinical symptoms appeared. According to Prof. Rabinowitz, “Many of us are chronically underhydrated without realizing it. And while we’ve long known that diet and exercise are crucial for heart health, hydration may be an overlooked third pillar.”

What now?

The takeaway is clear. If your blood test shows a serum sodium level above 140 mmol/L—even if it's technically within normal limits—it may be worth speaking to your doctor about your hydration habits. Most adults don’t meet even the lower recommended daily fluid intake, and chronic underhydration often goes unnoticed until damage is already underway.

With heart disease and hypertension affecting millions around the world, this Bar-Ilan–led study offers something rare in medicine: a simple, cost-effective way to catch problems early, when they’re still preventable. The next step in heart health may not be a new drug or a complex intervention. It might just start with a glass of water.

Test yourself: How much do you know about water?