How functional foods play critical roles in human health

How do functional foods affect human health? To answer this question it is important to understand what happens when food is digested and taken up by the gastrointestinal (GI) tract. The gut is a selective nutrient absorption system and the most important signal transduction and information exchange system within the body. It acts as a signal transducer, a neuroendocrine sensor, and an immunological recognition and presentation system. It is also a complex information exchange system comprising a number of signaling networks involving GI cells and cells immobilized in organs or transported in blood. The bioactivity of functional foods in vivo may be due to their effects on such networks, but this raises the question of what signaling pathways are used by non-nutrients that cannot be absorbed by the gut. The purpose of this review is to describe intestinal nutrient transportation, identify a number of widely expressed receptors and signal transduction pathways, and outline our current understanding of the mechanisms involved in health and disease. At the end of the review, a method for developing a cell communication network is described. This network is convenient for investigating the effects of oral administration of experimental medicines, drugs, or functional foods on cytokines of interest. Because cytokines and chemokines are transported via the circulatory system, a simple 2–3 mL blood sample from a volunteer is a rich source of information. This method may become the gold standard for evaluating the effects of functional foods or medicines in vivo.