Drink two litres of water a day: It’s a piece of advice widely given and widely ignored. Yet, new research suggests you do so at your peril.

According to the National Institutes of Health (NIH), people who stay well-hydrated appear to be healthier than those who don’t.

Water enthusiasts develop fewer chronic conditions, such as heart and lung disease, and they live longer.

Those who aren’t drinking enough water show more signs of biological ageing and are more likely to die earlier.

What’s the evidence?

The study analysed health data gathered from 11,255 adults over a 30-year period.

They investigated links between serum sodium levels – which increase when fluid intake drops – and various indicators of health.

They found that adults with serum sodium levels at the higher end of a normal range “were more likely to develop chronic conditions and show signs of advanced biological ageing than those with serum sodium levels in the medium ranges”.

Adults with higher levels were more likely to die at a younger age.

“The results suggest that proper hydration may slow down ageing and prolong a disease-free life,” said Dr Natalia Dmitrieva, a study author and researcher in the Laboratory of Cardiovascular Regenerative Medicine at the NIH.

Drinking plenty of water has numerous health benefits.

Biological ageing

Study participants were assessed during five medical visits. The first two visits were when they were aged in their 50s. The last visit was when they were between 70-90 years of age.

The serum sodium levels of participants were correlated with biological ageing, and were assessed using 15 health markers.

These included systolic blood pressure, cholesterol, and blood sugar. This provided insight about how well each person’s cardiovascular, respiratory, metabolic, renal, and immune systems were functioning.

The researchers also adjusted for factors like age, race, biological sex, smoking status, and hypertension.

The results

Adults with higher levels of normal serum sodium – with normal ranges falling between 135-146 milli-equivalents per litre (mEq/L) – were more likely to show signs of faster biological ageing, the NIH stated.

This was based on indicators like metabolic and cardiovascular health, lung function, and inflammation.

For example, adults with serum sodium levels above 142 mEq/L had a 10-15 per cent associated increased odds of being biologically older than their chronological age compared to ranges between 137-142 mEq/L.

Levels above 144 mEq/L correlated with a 50 per cent increase.

Further, levels of 144.5-146 mEq/L were associated with a 21 per cent increased risk of premature death compared to ranges between 137-142 mEq/L.

Chronic disease

Adults with serum sodium levels above 142 mEq/L had up to a 64 per cent increased associated risk for developing chronic diseases.

These included heart failure, stroke, atrial fibrillation and peripheral artery disease, as well as diabetes, and dementia.

Conversely, adults with serum sodium levels between 138-140 mEq/L had the lowest risk of developing chronic disease.

The findings don’t prove a causal effect and the findings need to be validated by randomised, controlled trials.

However, the researchers say “the associations can still inform clinical practice and guide personal health behaviour”.

And it won’t kill you to drink more water.