A daily juice did not crowd out whole fruit and veg

Most people fall well short of five portions of fruit and vegetables a day, and cost, preparation time and taste all get in the way. Juice and smoothies are an obvious workaround because they are quick and cheap to consume, but whether they should count towards the target is contested: critics argue they may displace whole fruit and vegetables or blunt the benefits. Until someone tests it directly, the argument runs on assumption. This trial set out to see what actually happens to total intake, and to mood and blood markers, when a daily juice portion is allowed inside standard UK 5-a-day advice.

Forty-two healthy adults who were already eating two servings of fruit and vegetables a day or fewer were randomly assigned to one of three groups for four weeks. One group acted as a control, one was asked to eat whole fruit and vegetables, and one was asked to eat whole fruit and vegetables plus one portion a day of fruit juice or a smoothie. All three groups received weekly financial support so that cost was not a barrier, and the two intervention groups also received an educational booklet developed with input from participants. The researchers tracked self-reported intake as the main outcome, alongside blood markers of intake and metabolism, mood, gut symptoms and how acceptable people found the approach.

Reported intake differed sharply between the groups. The whole fruit and vegetable group averaged 8.9 portions a day and the group that included juice averaged 6.6, both far above the control group's 2.45, and the difference between the two intervention groups did not reach statistical significance. Depression symptoms also differed across the groups, and were significantly lower in the juice group than in the control group. Nothing else moved: there were no differences in anxiety, in reported gut symptoms, or in the blood markers of intake and metabolism. Both interventions were rated as acceptable by the people following them.

The result cuts against the worry that letting juice count will cannibalise whole fruit and vegetable intake, at least over a month and at one portion a day. It does not settle the wider argument, because four weeks is too short for metabolic markers to shift much and the study cannot say whether people would keep it up once the weekly payments stopped. The gap between the two intervention groups was close to the conventional threshold for significance, so a larger study might yet find one. The funding came from a fruit juice industry body, and independent replication would carry more weight.

If getting anywhere near five portions a day feels out of reach, this is a reason to think a daily juice or smoothie need not sabotage the rest of your fruit and vegetable intake. It is not evidence that juice is equivalent to whole fruit, and the study found no change in any of the blood markers it measured. The lower depression scores in the juice group are interesting but came from a secondary measure in a small, short trial, so treat them as a hint rather than a finding. The practical signal here is about removing barriers: money and clear guidance moved intake a long way in four weeks.