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

Researchers at Liverpool John Moores University conducted a study revealing that individuals who did not meet daily hydration goals experienced notably elevated levels of the stress hormone cortisol when encountering stressful situations.

Continuous high cortisol levels have been associated with numerous health problems, 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. 

The participants’ hydration levels were monitored through urine and blood samples prior to undergoing a laboratory stress test, which was crafted to simulate a stressful real-world event.

Participants were given only ten minutes to prepare before entering a mock job interview scenario, where three individuals in lab coats awaited in a room with a staged camera.

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

The latest study revealed not hydrating enough gives you higher cortisol levels during stressful situations like a job interview

Cortisol levels, measured through saliva samples taken before and after the test, increased significantly more in participants who had consumed less water. This indicates that even mild dehydration can enhance the body’s stress reaction and may lead to health issues over time.

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

Regarding these results, a researcher noted: ‘We understand that individuals with low daily fluid consumption, who do not follow hydration guidelines, are likely to be inadequately 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.