Identifying the Best Tools for Recording Diet in Free-living UK Adults (SODIAT-2 Study)

The SODIAT project is a collaborative effort involving Aberystwyth University (AberU, project lead), University of Reading (UoR), Imperial College London (Imperial), and the University of Cambridge (UoC). Study 1, completed in July 2024, assessed the effectiveness of objective and subjective dietary intake assessment methods in highly-controlled clinical trial (protocol published at https://doi.org/10.12688/f1000research.155683.1) and informed the design of study 2.

Study 2 is led and sponsored by UoR. All study activities will be conducted remotely, with participants taking part from their usual locations (e.g., home, work).

►Screening and Welcome Week

Participants will use the online REDCap research platform to provide informed consent and complete a screening questionnaire to determine eligibility. Eligible participants will be contacted by a study researcher to discuss the study requirements, confirm consent, and schedule the study period.

A week before starting the 5-week study (Welcome Week), participants will be sent study materials/equipment and will be referred to the SODIAT webpage to view online video tutorials and read user guidelines for each study tool. Afterwards, participants will attend a video call with a study researcher to familiarize them with the study protocol and provide an opportunity to ask questions.

During the Welcome Week, participants will also self-collect a baseline blood sample (pre-video call) and complete the online eNutri FFQ to assess habitual diet. Within 2 days, they will then complete a condensed version of the FFQ to evaluate its effectiveness in estimating diet quality with reduced participant burden.

►5-week study period

Participants will follow their usual diet during weeks 1 \& 5 and record their diet using study tools (wearable cameras, blood samples, urine samples and online FFQ) for 3 consecutive days (Monitoring Weeks). During week 3 (Calibration Week), participants will use the same study tools as before whilst consuming the 3-day test diet. There will be two test diets (one diet for meat/fish consumers and another slightly adapted for non-consumers), consisting of foods and drinks that are common in the UK. During this controlled part of the study, participants will be requested to eat/drink all foods and drinks provided (delivered by an online supermarket) but cannot consume anything extra. They will receive recommendations on serving sizes for each food/drink but participants can choose how much they eat (either more or less).

►Wearable cameras

Participants will wear a small camera unit mounted on glasses (or attached to their own frames) during the 3-day periods of weeks 1, 3, and 5 (days 1-3; 15-17 and 32-34). The camera automatically captures still images every 7 seconds to document food and drink intake. The camera will be worn from waking to going to bed, although participants will be instructed to remove the camera during private times (e.g., bathroom), sensitive locations (e.g., changing rooms, GP surgeries) and if unsafe to wear (e.g., driving), and log these occasions, as well as the camera start time, on a paper-based log. At the end of the study, encrypted SD cards containing the images will be returned to the research team at Imperial for secure processing.

Images will be pre-processed using AI to exclude irrelevant images, and blur identifying details (e.g., faces, device screens). Only anonymised images will be analysed by researchers to estimate dietary intake.

►Capillary blood samples

When fasted, participants will self-collect blood samples using OneDraw kits on day 4 of each study week (day 4, 18 and 35), which collect a few drops of blood from the upper arm/thigh onto a filter paper cartridge. A baseline sample will also be collected during the Welcome Week. Instructions and video tutorials will be provided, and samples will be mailed to researchers at UoC for storage and biomarker analysis.

►Spot urine samples

Over 4 consecutive days of each study week (days 1-4, 15-18, 32-35), participants will collect first morning void and last evening void urine samples using straw and vacuum tube kits. Samples will be temporarily stored in a refrigerator before mailing them to AberU for processing where biomarkers of food and drink intake will be analysed.

►Online FFQ (eNutri)

Participants will complete the online eNutri FFQ on six occasions. Both the original (long-format) and condensed FFQ will be completed during Welcome Week to capture habitual intake during the previous 4 weeks. During the study, a 3-day, condensed FFQ adapted to capture foods/drinks not well-represented by biomarker analysis, will be completed at the end of each recording week (day 4, 18 and 35). During the test diet week, the original FFQ, adapted to capture 3-day intakes, will also be completed (day 18). The FFQ inputs, nutrient and food group intakes, and diet quality data will be exported in pseudonymised format for analysis.

At the study's conclusion, participants will complete a short, online usability questionnaire about the study tools via REDCap (day 35).

Participants will mail their blood and urine samples at designated timepoints using pre-paid postage, and return all study equipment and logs at the end of the study via a courier collection.

Researchers will monitor adherence and communicate with participants as needed. Daily reminders will also be sent via email or text (SMS) message during the recording days.

► Statistical analysis

Accuracy of integrating multiple dietary assessment technologies to report dietary intake in free living environments will be measured during the calibration week (week 3) using dietary intake data collected from wearable cameras, spot urine samples, capillary blood samples, and self-reported FFQs.