Hydration depends on things like body type and activity level, but it’s critical that we all stay hydrated (Credits: Getty)

We all know that drinking enough water is good for our health and ultimately keeps us alive.

But a new study has shown just how important it is to stay well hydrated.

The study, published in the medical journal The Lancet, is the result of 25 years of research among 11,255 adults. So it’s pretty convincing.

And the National Institutes of Health researchers found that those who don’t drink enough water age faster and become more susceptible to chronic diseases that cause premature death.

Over the course of the two and a half decades, researchers asked participants questions about the family’s socioeconomic status and medical history. Meanwhile, clinical tests for sodium in her blood served as an indicator of her fluid intake.

Those who had more sodium in their blood (ie, less hydrated) were 50 percent more likely to show physiological signs of aging. These include things like high cholesterol and sugar, as well as physical signs like dry skin and sunken eyes.

Eating fruits and vegetables also helps get fluids into your system (Credits: Getty)

“The results suggest that adequate hydration can slow aging and extend a disease-free life,” said researcher Natalia Dmitrieva of the National Heart Lung and Blood Institute (NHLBI) in Maryland.

The study’s authors conclude that measuring sodium in the blood, and thereby determining hydration levels, can help physicians take action when dealing with patients. For example, they may ask patients to increase their fluid intake by both drinking more and eating foods such as fruits and vegetables.

How many liters of water should you drink per day?

The NHS Eatwell guide says you should drink about 6-8 cups or glasses of water a day.

While it doesn’t say how big these should be, other estimates, such as those from the British Dietetics Association, have suggested that you should aim for about 1.5 to 2 liters of water.

However, the guidance has changed over the years – and the long-held belief that you should be drinking eight glasses a day may be too much.

In 2010, the European Food Safety Authority suggested that men should drink two liters and women 1.6 liters per day.

For men that is three and a half pints, for women almost three pints.

An average bottle of water contains about 500 ml, so a man should drink four bottles a day and a woman just over three.

However, this can also be influenced by several factors, including age and your circumstances.

According to the British Dietetics Association, children under 14 need less than adults – while pregnant and breastfeeding women should drink more, with the Association recommending an extra 300ml a day if you’re pregnant and 700ml more a day if you are breastfeeding.

If you exercise or play sports, you should also drink more to compensate for the fluid loss through sweating.