The Nottingham GI MRI group has been at the forefront of elucidating the effects of poorly digested carbohydrates on gastrointestinal physiology. the investigators have published techniques to measure free water in the small bowel and assessment of viscosity in the colon using MR relaxometry. This includes the demonstration that fructose ingestion on its own leads to increased free water in the small bowel compared to co-ingestion with glucose - see panel. The investigators wish to apply these techniques to compare the effect of different foods: white bread, lettuce and rhubarb. The investigators have previously shown that bread led to a reduction in small bowel water and so can active as a negative control. Rhubarb should serve as a positive control.