Thirsty? Your blood pressure might be too—skipping water could wreck your heart

A 20-year review of health records from more than 407,000 Israeli adults shows that blood-sodium levels near the top of the “normal” range are linked to sharply higher risks of hypertension and heart failure.

The Bar-Ilan University team concludes that better hydration, which naturally lowers sodium concentration, may be an overlooked but effective way to prevent chronic cardiovascular disease.

Researchers at Bar-Ilan University analysed electronic records from Leumit Healthcare Services covering 407,992 apparently healthy adults over 20 years. Published in the European Journal of Preventive Cardiology, the study re-examined the conventional “normal” serum-sodium band of 135–146 mmol/L and found that risks escalate well before the upper cut-off.

Participants whose sodium readings fell between 140 and 146 mmol/L were more likely to develop high blood pressure and heart failure, even after adjusting for age, sex, body mass index, smoking, potassium levels and baseline blood pressure. Once sodium exceeded 143 mmol/L, the odds rose by 29 percent for hypertension and 20 percent for heart failure.

Lead author Professor Jonathan Rabinowitz said the data “point to hydration as a critical and under-recognised pillar of chronic disease prevention”. Because blood sodium rises when the body is under-hydrated, the team used it as a surrogate marker for long-term fluid intake. Nearly 60 percent of the cohort sat in the risk-associated zone, underscoring how common mild under-hydration may be.

The researchers excluded anyone with conditions that disturb water balance to isolate hydration’s impact. They stress that the findings do not invalidate existing sodium guidelines but rather highlight the importance of adequate fluid intake.

Current guidance from the US National Academies of Sciences, Engineering and Medicine recommends about 3.7 litres of total daily fluids for men and 2.7 litres for women, though individual needs vary with climate, activity and health. The authors suggest clinicians consider serum sodium as a low-cost screening tool to identify patients who might benefit from simple lifestyle advice—starting with an extra glass or two of water each day.