Not drinking enough water could trigger an alarming health problem - and it's not dehydration

Not drinking enough water could be triggering higher stress levels and increasing the risk of serious health problems, scientists have warned.

A study by researchers at Liverpool John Moores University found that people who failed to meet daily hydration targets had significantly higher levels of the stress hormone cortisol during high-pressure situations.

Persistently raised cortisol has been linked to a range of health issues, including high blood pressure, heart disease, type 2 diabetes, obesity, depression and anxiety.

Chronic stress is also known to weaken the immune system, leaving people more vulnerable to illness.

The trial involved 32 volunteers, half of whom were limited to just 1.5 litres of water a day while the other half followed the recommended intake.

Hydration levels were tracked using urine and blood samples before they faced a laboratory stress test designed to mimic a nerve-racking real-life scenario.

Each participant was asked to prepare for just ten minutes before walking into an impromptu job interview, where three people in white coats were waiting in a room rigged with a fake camera.

Immediately afterwards, they were challenged to complete a rapid-fire mental arithmetic task, subtracting numbers as quickly as possible.

Saliva samples collected before and after the test showed that cortisol levels spiked much more sharply in those who had drunk less water, suggesting that even mild dehydration may heighten the body's stress response and, over time, contribute to poor health.

Professor Neil Walsh, of the LJMU School of Sport and Exercise Sciences, described the test as 'really flustering'.

On their findings, he said: 'We know that people who have a low daily fluid intake, who don't meet the recommendations, are likely to be poorly hydrated.

'But what we didn't know was whether, when you then stress those people under controlled conditions, they would have a greater stress hormone response.'

However, he noted that physical signs of stress such as increased heart rate, sweaty hands and dry mouth were similar in both groups.

'Both groups felt equally anxious and experienced similar increases in heart rate during the stress test,' he said.

'But the people who were poorly hydrated, because they were not drinking enough water each day, had much greater cortisol responses.'

The low-fluid intake group also did not report feeling thirstier than those who drank more, according to Prof Walsh.

He explained: 'Cortisol is the body's primary stress hormone and exaggerated cortisol reactivity to stress is associated with an increased risk of heart disease, diabetes and depression.

'If you know you have a looming deadline or a speech to make, keeping a water bottle close could be a good habit with potential benefits for your long-term health.'

But Prof Walsh added further research is needed to better understand the findings, recently published in the Journal of Applied Physiology.

This includes seeing if increasing water intake in those who do not drink enough can reduce responses to daily 'micro stressors' like traffic jams or presentations at work.

'We'd like to think that meeting the water intake guidelines could be one of a number of things you could do to blunt that cortisol response day to day,' he said.

In the UK, health chiefs suggests adults should drink between six and eight cups of fluid a day, which is roughly 1.5 to two litres.

However, people may need to drink more when it is hot, if they are very active, if they are recovering from an illness, or if they are pregnant or breastfeeding.

Just earlier this year, analysis by the British Heart Foundation (BHF) found rising deaths among working aged adults from heart disease.

Cardiovascular deaths in working age adults have risen by 18 per cent in the UK since 2019, from 18,693 to 21,975 in 2023, averaging 420 a week.