Comparing Approaches to Increasing Fruit and Vegetable Intake and Their Influence on Metabolic Health

The number of daily portions of fruit and vegetables consumed (including fruit juice in group 3) will be determined by 4 x 24-hour dietary recalls using the validated dietary recall software Intake24 (Foster et al., 2019).

The 6-item fruit and vegetable screener module from the BRFSS (Behavioral Risk Factor Surveillance System; CDC, 2020) will be used as a secondary measure to capture self-reported fruit and vegetable intake pre- and post-intervention. Data will be compared against the more granular dietary data from Intake24, to evaluate agreement and suitability of this tools for use as an outcome measure in future fruit and vegetable-based interventions.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of plasma ascorbic acid (μmol/L), or vitamin C, will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid lutein (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid zeaxanthin (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid beta-cryptoxanthin (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid lycopene (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid alpha-carotene (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample for determining objective biomarkers of fruit and vegetable intake. Concentration of the serum carotenoid beta-carotene (μmol/L) will be measured via high-performance liquid chromatography (HPLC) using methods well-validated in our laboratory. These markers will help verify any participant-reported changes in fruit (including juice) and vegetable intake.

Prior to and following the intervention, participants will provide a fasted blood sample to determine markers of metabolic health. The Nightingale metabolomic biomarker panel, assessed pre- and post-intervention using Nuclear Magnetic Resonance (NMR) spectroscopy, will be used to evaluate the impact of the intervention on markers of metabolic health.

The impact of the study interventions on symptoms of depression will be evaluated by administering the PHQ-9 questionnaire (a validated tool to measure levels of depression) pre- and post-intervention. Participants will provide information on the frequency with which they have been affected by depression-related symptoms (from not at all to nearly every day). There are four options for participants to select and each is associated with a score (not at all (0), several days (+1), more than half the days (+2), nearly every day (+3)). The sum of these scores indicates the level of depression severity (0-4 none/minimal; 5-9 mild anxiety; 10-14 moderate; 15 -19 moderately severe; 20-27 severe).

The impact of the study interventions on anxiety symptoms will be evaluated by administering the GAD-7 questionnaire (a validated tool to measure levels of anxiety) pre- and post-intervention. Participants will provide information on the frequency with which they have been affected by anxiety-related symptoms. There are four options for participants to select, and each option is associated with a score (not at all (0), several days (+1), more than half the days (+2), and nearly every day (+3)). The sum of these scores indicates the level of anxiety (0-4 minimal; 5-9 mild anxiety; 10-14 moderate anxiety; greater than 15 severe anxiety).

Participants will complete the gut symptoms questionnaire (Winham and Hutchins, 2011) pre- and post-intervention. This involves responding to 4 close-ended questions (yes/no) enquiring about changes in the frequency of flatulence, stool frequency, stool consistency, or bloating frequency in the past week. The total number of symptoms the participant reported as having increased in the last week is their gut symptom score.

Participants will complete the gut symptoms questionnaire (Winham and Hutchins, 2011) pre- and post-intervention. One of these items is a close-ended question (yes/no) enquiring about changes in the frequency of flatulence in the past week. If participants report a change, they will be asked to indicate the direction (increase/decrease) and magnitude of change (from 1 = least change to 5 = greatest change on a 5-point likert scale).

Participants will complete the gut symptoms questionnaire (Winham and Hutchins, 2011) pre- and post-intervention. One of these items is a close-ended question (yes/no) enquiring about changes in stool frequency in the past week. If participants report a change, they will be asked to indicate the direction (increase/decrease) and magnitude of change (from 1 = least change to 5 = greatest change on a 5-point likert scale).

Participants will complete the gut symptoms questionnaire (Winham and Hutchins, 2011) pre- and post-intervention. One of these items is a close-ended question (yes/no) enquiring about changes in stool consistency in the past week. If participants report a change, they will be asked to indicate the direction (increase/decrease) and magnitude of change (from 1 = least change to 5 = greatest change on a 5-point likert scale).

Participants will complete the gut symptoms questionnaire (Winham and Hutchins, 2011) pre- and post-intervention. One of these items is a close-ended question (yes/no) enquiring about changes in bloating frequency in the past week. If participants report a change, they will be asked to indicate the direction (increase/decrease) and magnitude of change (from 1 = least change to 5 = greatest change on a 5-point likert scale).

Acceptability of the interventions will be assessed post-study via a custom questionnaire, using 5-point visual analogue scales and informed by the Theoretical Framework of Acceptability (Sekhon et al., 2017).