Effect of wholegrain structure on metabolism and breath volatile organic compounds

This study is a randomised crossover design to measure the postprandial blood glucose and breath volatile organic compound (VOC) response to wholegrain breads of differing structure. The trial includes three food exposures: * A bread made from finely milled wholegrains (100% wholegrain flour) providing 50g available carbohydrate (approx. four slices) served with 250mL water * A bread made from of mixture of finely ground and intact wholegrains providing 50g available carbohydrate (approx. four slices) served with 250mL water * A 250ml glucose drink as a control (at a glucose concentration of 20g/100mL) Both breads are matched for available carbohydrate and fibre content, and only differ in the particle size and structure of the wholegrains. All three foods will provide 50g of available carbohydrate. Intervention order will be randomised for the three foods. A washout period of 3 days will be adhered to between testing days. Key measures: 1. Blood glucose levels are being measured from capillary blood obtained via finger prick. 2. Blood short chain fatty acids acetate, butyrate and propionate are being measured from venous blood collected from the arm. 3. Breath VOCs (Including short chain fatty acids) will be measured from breath using both Gas chromatography mass spectrometry (GC-MS) and Proton transfer reaction mass spectrometry (PTR-MS) Participants will arrive at the research clinic between 8:00am and 9:30am after a minimum 10 hour water only fast. A text reminder will be sent 24 hours before to remind participants to follow their similar dietary and exercise pattern, and to fast from 10pm that evening. Before their first visit a food and exercise diary will be completed and used to remind participants. Participants will be asked to sit for at least 10 minutes, to stabilise heart rate and breathing rate levels. A questionnaire asking about any changes since the last visit and adherence to study requirements the day before will be completed. On the first visit a food frequency questionnaire will be completed to measure usual intake. Two capillary blood samples will be taken by finger prick for the measurement of baseline fasted blood glucose and one 6mL venous blood sample will be taken by a nurse. One single, full breath will be captured into a tedlar bag for GC-MS analysis, and three exhaled breaths into the PTR-MS before the test food will be provided. Participants will have 10 minutes to consume the test foods alongside 250mL of water. The participant will provide three fully exhaled breaths into the PTR-MS and one capillary blood glucose will be taken at 30, 60, 90, 120, 180, 240, 270, 300, 330, 360 minutes following consumption. Breath samples will be provided using a clean, dedicated mouthpiece according to an established protocol*. At 180 minutes post consumption, another portion (same size as at baseline) of the test food will be provided with 250mL of water with 10 minutes allowed to consume. At 300 minutes post consumption, a second fully exhaled breath into a tedlar bag and 6mL venous blood sample will be collected. A total of 12mL of venous blood will be collected each test day. Physical activity and meals in the 24 hours before each intervention will be standardised and participants asked to abstain from alcohol and strenuous exercise. Participants will be required to stay at the research clinic for approximately 6.5 hrs on each test day. During the six hours of testing, participants will be encouraged to sit for the duration, moving only for the toilet, to wash their hands before each capillary finger prick and for breath measures. However, participants will be able to undertake their own activities such as reading, working on a computer, watching TV on their computer, or relaxing. At the end of each 6 h testing session, a small meal will be provided. * Participants are seated in front of the breath testing buffer tube with feet flat and knees at 90 degrees, and back straight and vertical. They then inhale fully, hold for 2 seconds, before bringing their mouth to the breath buffer tube and fully exhaling steadily and with control.