The matrix of a food can significantly affect how well humans can absorb and use nutrients. Plants like fruits, vegetables, nuts, grains, and legumes have cell walls that form a network around their cells. These cell walls are a barrier for the digestive system to break down completely, which can make it harder to digest the food and get energy from it. This study will explore how the integrity of plant cell walls affects how well humans can absorb macronutrients (protein, fat and carbohydrates) and beneficial compounds e.g. phytochemicals. The study will compare two chickpea meals that have similar nutrients and energy content but differ in the amount of intact plant cell walls e.g. chickpea salad meal (INTACT diet) and chickpea burger meal (BROKEN diet).

The energy content of food can be in principle calculated by multiplying the content of each energy-yielding substrate by the corresponding heat of combustion. However, only part of this energy yielding substrates is converted to energy because of their incomplete digestion and absorption in the gastrointestinal tract. The structural composition of foods, known as the food matrix, significantly affects nutrient bioavailability. One such structural feature is the integrity of plant tissues characterised by the interconnected, continuous network of cell walls which surround and protect plant cells. When cellular integrity is retained, macronutrients are naturally "encapsulated" within cell walls which effectively reduces the rate and the extent of their digestibility by 6-7% compared to a diet poor in plant-based foods. This study aims to investigate the effect of plant tissue integrity on the total energy excretion of a diet, bioavailability of macronutrients and bioactive compounds, and on plasma levels of glucose, essential amino acids and triglycerides. The investigators will do this by comparing two diets which have (approximately) the same composition in macronutrients and energy but different levels of plant tissues integrity, namely a diet rich in intact plant tissues (INTACT diet), and a diet poor in such intact plant tissues (BROKEN diet). The investigators will use an ileostomy model to be able to determine the difference in energy excretion at the level of the terminal ileum.

Inclusion Criteria:

• Previously had an ileostomy
• ≥1.5-years post-operative
• Aged 18-60 years
• Males and females (not currently pregnant/lactating)
• Non-smokers
• Not allergic to nuts and celery

Exclusion Criteria:

• Never had an ileostomy
• <1.5-year post-operative
• Not aged 18-60 years
• Pregnant/lactating female
• Smokers
• Allergic to nuts and celery