The Scottish Bowel Screening Programme is an enormous potential research resource; half a million people in Scotland do their bowel screening test each year. If we could obtain meaningful data on the gut microbiota in these individuals, many clinical questions could be answered using nested case-control studies relating gut microbiota profiles to cancer, obesity, cardiovascular and metabolic diseases and Alzheimer's disease. As individuals are screened from age 50 to 74 years, there would also be excellent opportunities for longer-term longitudinal studies. Since 2017, the bowel screening programme has used qFIT testing for faecal haemoglobin. Patients collect a tiny (2 miligram) sample of their faeces into 2 mililiter of buffer but only approximately 6 microliter is required for testing. The goal of this study is to investigate whether the large number of patients' samples available from the National Bowel Screening Programme could be used in future gut microbiome studies using the leftover faeces in buffer in the qFIT tests.