Intake of food for long-term sustained activities recommends a mixture of slowly digestible starch and rapidly available glucose (RAG). That way, even through long arduous activities, energy supply is ensured. The time taken to digest different starch elements was previously thought to be the reason for the continual-release energy effect. Partners from the EU funded project 13C-STARCH have broken new ground to unravel the complexities of the glucose metabolic pathways after the breakdown of starch. Previously, glycaemic index and time for digestion have received most of the research attention. However, project consortium partners also investigated the different sources of glucose after a meal. These involved glucose produced endogenously and tissue distribution. In order to achieve this, they compared two different types of food. They produced a traceable source of starch in wholemeal bread baked from wheat grown in 13C carbon dioxide. Four healthy men were given wholemeal bread or glucose in water in a crossover trial. To monitor endogenous glucose production, a continuous infusion of D-[6,6-2H2] glucose as a tracer was also administered. During the six hour period after a meal, the traceable carbon was measured in breath as carbon dioxide together with plasma glucose and insulin levels. The data collected questions the reasons behind observed blood glucose levels. Initial insulin levels were around 40% lower after wheat bread than with glucose. However, glucose production was suppressed after wheat bread as compared with glucose in water. It would appear therefore that rate of digestion of starch is not totally responsible for this effect and there are other factors, possibly within the composition of the wheat bread. Starch products, including bread are the staple food of many areas of the world. There is therefore scope for food companies to create a truly functional food out of a basic staple that helps to prevent chronic disease.