Drinking a glass of 100% fruit juice or a smoothie every day may help improve mental well-being, particularly among people who eat relatively little fruit and vegetables, according to a study by researchers at Newcastle University.

The four-week randomized trial involved adults who normally consumed two or fewer portions of fruit and vegetables a day. Researchers provided support to help participants increase their intake toward the recommended five portions a day.

Some participants were asked to eat whole fruits and vegetables only, while another group was encouraged to include a daily glass of fruit juice or a smoothie along with whole fruits and vegetables.

After four weeks, both groups had increased their fruit and vegetable intake. However, those who included fruit juice or smoothies also reported lower levels of depression.

The findings, published in the peer-reviewed British Journal of Nutrition, showed that the fruit juice and smoothie group had depression scores 2.52 points lower on a 27-point scale than the control group.

Researchers described the difference as modest but statistically significant.

Dr Courtney Neal, who conducted the study while at Newcastle University and is now at the University of Liverpool, said many people find it difficult to meet the recommended five daily portions of fruit and vegetables.

“Our trial showed that when people with low fruit and vegetable intake were given financial and educational support to overcome common barriers, they were able to make meaningful changes to their diet,” she said.

She said simple and affordable options, such as a small daily glass of 100% fruit juice or a smoothie, could help people reach the recommended intake and potentially support mental well-being.

Fiber intake also increased
Dietary records showed that participants in both groups that received dietary support increased their daily fiber intake by an estimated 8 to 10 grams.

This suggested that participants who drank juice or smoothies continued to add other fiber-rich fruits and vegetables to their diets.

The study involved 42 people. Researchers found no harmful changes in metabolic health markers among those who consumed fruit juice or smoothies during the four-week trial, despite concerns about the sugar content of fruit juice.

Dr Oliver Shannon, a lecturer in nutrition and ageing at Newcastle University and one of the study’s senior authors, said the cost of fresh produce can make it difficult for some people to increase their fruit and vegetable intake.

“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,” he said.

Shannon said the lower depression scores among those who drank fruit juice were encouraging but required further research, particularly among people experiencing poor mental well-being.

He also pointed to earlier research suggesting that citrus juices may improve blood flow to the brain and support cognitive function.

How the study was conducted
The 42 participants were randomly divided into three groups of 14.

The first group continued with their usual diet and served as the control group.

The second group received financial and educational support to increase their intake to five portions a day using whole fruits and vegetables.

The third group received the same support but was also asked to drink one glass of fruit juice or a smoothie each day.

All participants received £10 a week, while the two groups receiving dietary support were also given educational materials to help them change their eating habits.

Researchers assessed participants’ anxiety and depression levels using standard questionnaires known as GAD-7 and PHQ-9.

The group that included fruit juice or smoothies recorded significantly lower depression scores than the control group. Its adjusted average score was 2.93, compared with 5.45 for the control group.

Participants also completed four dietary records during the study, reporting what they had eaten during the previous 24 hours.

The researchers estimated that both groups receiving dietary support increased their daily fiber intake by 8 to 10 grams.

The study was funded by the Fruit Juice Science Centre.

Source: Science Daily