Just one glass of juice a day could help boost mood and ward off depression, new research has suggested. 

Eating more fruits and vegetables has long been associated with better physical health - with a daily intake of just 200g shown to slash the risk of heart disease, stroke, cancer and even premature death. 

Now, researchers claim adding a daily glass of fresh fruit juice, or a smoothie, to your diet could even improve mental wellbeing. 

Fewer than one in five adults and one in ten teenagers meet the UK's five-a-day guidance for fruit and vegetable intake. 

Poor mental health, meanwhile, is soaring. According to the latest figures, almost 500,000 young people have sought help for mental health problems from A&E units alone in England since 2019. 

More than a fifth of 14 to 29-year-olds report high levels of depressive symptoms by the age of 23. 

The study - led by researchers at Newcastle University - found that eating five portions of fruit and vegetables a day alongside a glass of fruit juice or a smoothie significantly improved symptoms of anxiety and depression.

Those who increased their fruit and vegetable intake without the juice or smoothie didn't experience the same benefits, however. 

Dr Courtney Neal, the study's lead author, said: 'While most people know eating five-a-day can be good for our health, many people struggle to. 

'Our trial showed that when people with low fruit and vegetable intake were provided with targeted financial and educational support to address common barriers to eating five-a-day, they were able to make meaningful changes to their diet. 

'We found that simple, cost-effective solutions, like drinking a small glass of 100 per cent fruit juice or a smoothie daily, could help people reach their five-a-day, with potential benefits for mental well-being.' 

The study - published in the British Journal of Nutrition - followed 42 adults who typically ate two or less portions of fruit and vegetables a day. 

Of these, 28 increased their daily fruit and vegetable intake to five-a-day, for a period of four weeks. 

Half of this group also drank a glass of fruit juice or a smoothie every day. 

The remaining 14 participants followed their diet as normal. 

All groups received £10 a week, with the healthier eating groups also given educational material to help support their dietary changes. 

The impact of diet on participants' mood was measured using validated questionnaires for anxiety and depression. 

Results showed that those drinking fruit juice or smoothies alongside their five-a-day scored nearly 3 points lower on markers for depression than other groups.

And despite ongoing concerns around fruit juices' sugar content, results showed no adverse effects on metabolic health markers among participants drinking a daily glass - in line with the UK's official guidance. 

Dr Oliver Shannon, an expert in nutrition and ageing and the study's co-author, said: 'Given the ongoing cost of living pressures in the UK, the price of fresh produce is often a barrier for people trying to eat more fruit and vegetables.

'Our study shows that drinking a daily glass of fruit juice or a smoothie could be part of the solution and help people reach five-a-day fruit and vegetable targets.

'The finding that fruit juice drinkers had reduced depression scores is promising and worthy of further exploration, particularly in individuals experiencing poor mental wellbeing,' he added. 

'It backs up studies which report improved brain blood flow and cognitive function after people drink citrus juices. 

'Simple dietary changes - like increasing fruit intake, including through a daily glass of juice - could play a role in supporting mental wellbeing,' he concluded.

Previous studies, involving nearly 9,000 children in primary and secondary schools, found that those who eat five or more portions of fruit and vegetables a day have the best mental health. 

Another Australian study found that people with moderate to severe depression who altered their diet to include more wholegrains, leafy vegetables, healthy fats and fibre - known as the Mediterranean diet - were able to attain remission. 

But, while adding fruit juice or smoothies to your diet can provide a potent source of vitamins, minerals and phytochemicals, such as polyphenols - it should only be encouraged within the context of a healthy balanced diet, experts say.

This is because juice is also extremely high in sugar - mainly in the form of fructose. 

Consuming too many of these so-called free sugars - released when fruit is crushed - can increase the risk of tooth decay, obesity and type 2 diabetes.