- A small UK trial found people who added a daily glass of 100% fruit juice or a smoothie while improving their diet had lower depression scores after four weeks.
- Both intervention groups increased fruit, vegetable and fibre intake.
- For people with diabetes, the finding needs caution because fruit juice can raise blood glucose quickly.
Fruit juice has a complicated reputation.
It can help people increase fruit intake, but it can also deliver sugar quickly and without the fibre of whole fruit.
A small Newcastle University trial adds another layer to the debate.
Researchers recruited 42 adults who were eating two or fewer portions of fruit and vegetables a day.
Some were supported to reach 5-a-day using whole fruits and vegetables only.
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Others were supported to increase whole fruit and vegetables while also adding one daily glass of 100% fruit juice or a smoothie.
After four weeks, both intervention groups had increased their fruit and vegetable intake.
Both also increased fibre intake by around 8 to 10g per day.
But the group including juice or smoothies had lower depression scores than the control group.
The difference was modest but statistically significant.
That is interesting, especially because diet and mental wellbeing are increasingly being linked in research.
Fruit and vegetables provide polyphenols, vitamins, minerals and other compounds that may influence inflammation, blood flow and brain function.
Citrus juices in particular have been studied for possible effects on brain blood flow and cognition.
But this is not a free pass to drink large amounts of juice.
The study was small, lasted only four weeks and was funded by the Fruit Juice Science Centre.
It also did not focus on people with diabetes.
That matters because fruit juice can raise blood glucose rapidly.
For someone with type 2 diabetes, prediabetes or insulin resistance, whole fruit is usually a better option because it comes with fibre and tends to be more filling.
If juice is used, it should be a small glass and counted as part of total carbohydrate intake.
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The useful message is broader.
Helping people reach 5-a-day may need practical, affordable options.
Not everyone can regularly buy and prepare fresh produce.
A small glass of 100% juice or a smoothie may help some people move in the right direction, especially if it does not replace whole fruit and vegetables.
For diabetes, the priority remains balance.
Mood matters, fruit intake matters and blood glucose matters too.
