Effects of a dietary fibre supplement on blood glucose after meals in healthy adults consuming a diet higher in processed foods

Active dietary fibre intervention during dietary periods higher in processed foods Trial overview This is a double-blind, randomised, two-period, two-sequence cross-over trial. Each participant will complete a 14-day active dietary fibre condition and a 14-day matched placebo condition in random order. The two intervention periods will be separated by a washout period of three to six weeks. The intervention will be undertaken under free-living conditions in Dunedin. Participants will attend five in-person study visits facilitated by trained members of the research team. Blood pressure and other research-team assessments will be conducted in a clinic room on the 9th floor of Dunedin Hospital. Fasting venous blood samples at Visits 2, 3, 4 and 5 will be collected by trained phlebotomists at the Awanui Labs collection site at Dunedin Hospital. Participants are expected to spend approximately two hours in total attending the five visits. Visit 1 – baseline and screening visit Visit 1 will occur before the run-in period and will take approximately 30 minutes. A trained member of the research team will explain the study procedures, answer questions and obtain written informed consent. Height, body weight and blood pressure will be measured. Participants will complete the baseline study questionnaires and receive instructions for completing the four-day food diary. A continuous glucose monitoring sensor will be inserted by a trained member of the research team to measure glucose under usual dietary conditions during the run-in period. Run-in period Following Visit 1, participants will complete an approximately 14-day run-in period. During this period, participants will continue their usual diet and lifestyle and will not consume either study product or the study-provided processed foods. Participants will wear a continuous glucose monitoring sensor to obtain glucose measurements under their usual dietary conditions. They will also complete a four-day food diary covering three weekdays and one weekend day. Participants will record all foods and beverages consumed, including food type and brand, preparation method, portion size and time of consumption. The run-in period will provide baseline dietary and glucose data before the first intervention period. Visit 2 – pre-intervention assessment for Intervention Period 1 Visit 2 will occur immediately following the run-in period and immediately before the first 14-day intervention period. The visit will take approximately 20 minutes. Body weight and blood pressure will be measured, and a fasting venous blood sample will be collected by a trained phlebotomist at Awanui Labs. The run-in continuous glucose monitoring sensor will be removed and its data uploaded for analysis. Participants will complete the study questionnaires, and the research team will review the run-in food diary. Participants who remain eligible after review of the screening and baseline results will be randomised to their intervention sequence. A new continuous glucose monitoring sensor will be inserted for the first intervention period. Participants will receive their allocated study product in a study container with the dosing record incorporated into its label, together with written instructions. The research team will arrange collection or delivery of the participant's selected processed supermarket foods for the first week of the intervention period. Visit 3 – end of Intervention Period 1 Visit 3 will occur at the conclusion of the first 14-day intervention period, on or immediately after Day 14, and will take approximately 30 minutes. Body weight and blood pressure will be measured. A fasting venous blood sample will be collected by a trained phlebotomist at Awanui Labs. The continuous glucose monitoring sensor will be removed and its data uploaded for analysis. Participants will complete the end-of-period questionnaires and return the study product container with its completed dosing record and any unused study product. The research team will review the participant's four-day intervention-period food diary. A semi-structured interview of approximately 15 minutes will be conducted by a trained member of the research team to explore the participant's experience of the study foods and study product. Participants will then commence a washout period of three to six weeks, during which they will return to their usual diet and will not consume either study product or the study-provided foods. Visit 4 – pre-intervention assessment for Intervention Period 2 Visit 4 will occur at the end of the washout period and immediately before the second 14-day intervention period. The visit will take approximately 10 minutes. Body weight and blood pressure will be measured, and a fasting venous blood sample will be collected by a trained phlebotomist at Awanui Labs. Participants will complete the study questionnaires. A continuous glucose monitoring sensor will be inserted for the second intervention period. Participants will receive the alternative study product in a study container with the dosing record incorporated into its label, together with written instructions. The research team will arrange collection or delivery of the same selection of processed supermarket foods provided during the first intervention period. Visit 5 – end of Intervention Period 2 Visit 5 will occur at the conclusion of the second 14-day intervention period, on or immediately after Day 14, and will take approximately 30 minutes. Body weight and blood pressure will be measured. A fasting venous blood sample will be collected by a trained phlebotomist at Awanui Labs. The continuous glucose monitoring sensor will be removed and its data uploaded for analysis. Participants will complete the end-of-period questionnaires and return the study product container with its completed dosing record and any unused study product. The research team will review the participant's four-day intervention-period food diary. A second semi-structured interview of approximately 15 minutes will be conducted by a trained member of the research team. Approximately eight weeks after Visit 5, participants will complete an online follow-up session with a member of the research team to determine whether they have returned to their usual dietary pattern. Dietetic support will be arranged if a participant reports difficulty returning to their usual diet. All study visits and intervention-related contacts will be conducted individually rather than in a group setting. Provision of processed supermarket foods At baseline, each participant will select up to eight commonly consumed processed supermarket foods from a predefined list. The same selection of foods will be provided during both intervention periods. The foods will be supplied twice during each 14-day intervention period: once at the beginning of Week 1 and again at the beginning of Week 2. Participants may collect the foods from a designated supermarket or have them delivered to an agreed address. The research team will coordinate the supermarket orders and will contact participants midway through each intervention period to confirm whether any additional study-provided foods are required. Participants will be instructed to use the study-provided foods to replace some foods within their usual dietary pattern where appropriate. The study-provided foods are not intended to replace the participant's entire dietary intake, and participants will not be instructed to increase their total food intake. Active dietary fibre condition During the active condition, participants will receive No.2 Kiwi Berry Good Gut Fibre in a 200 g study container. Participants will be instructed to mix one teaspoon, weighing approximately 4–5 g and providing approximately 2.9–3.7 g of dietary fibre, with one cup of water and consume it three times daily, preferably with the three main meals, for 14 days. Participants will also be instructed to maintain adequate fluid intake throughout the intervention period. Assessment of adherence to the study product Adherence to the active study product or matched placebo will be assessed using the dosing record incorporated into the study product container label. Participants will record each of the three prescribed daily doses on the label throughout each 14-day intervention period. The research team will review the completed dosing record at the end of each intervention period. Adherence will be calculated as the proportion of prescribed doses recorded as consumed. Participants will also return the study product container and any unused study product. Monitoring consumption of the study-provided processed foods Consumption of the study-provided processed foods will be monitored but will not be assessed as a separate quantitative adherence outcome. During each intervention period, participants will complete a four-day food diary covering three weekdays and one weekend day. The diary will record the type, brand, amount and timing of all foods and beverages consumed, including the study-provided foods. Trained researchers will review each food diary for completeness and clarity and will contact the participant to clarify missing or ambiguous entries where necessary. The midway check-in during each intervention period will also be used to confirm whether additional study-provided foods are required.