To address potential effects of the polyphenol-rich plant products on absorptive capacity by a changed villus height:crypt depth ratio, histological sections from duodenum and jejunum were analysed as these parts of the small intestine are the main sites of absorption of nutrients and histological changes can be expected in these parts of the small intestine [ 4].
The intestine has a large reserve capacity for digestion and absorption of nutrients which is due to both excess function and to adaptive changes which increase function in one segment of the digestive-absorptive system when it is decreased or lost in another segment.
Food conversion involves, first, the breakdown of food substances leading either to their absorption or to their egestion and, then, the post-absorptive processing of nutrients leading either to their assimilation as body mass, to their consumption as energy, or to their excretion either because they are too costly to process or because they could potentially accumulate to toxic levels.
Acetycholine (ACh) is released by intra-pancreatic vagal nerve endings and activates muscarinic acetylcholine receptors (mAChRs) on pancreatic β-cells during both the pre-absorptive (cephalic phase) and absorptive phases of nutrient intake [ 1– 3].
Damage to the intestinal epithelium leads to a decreased absorptive surface area and less availability of nutrients for growth and development [ 3, 7].
This specialization is apparent in a series of large and small invaginations of the intestine formed by villi and microvilli, which serve to greatly increase the absorptive surface area of the brush-border for the efficient digestion and absorption of dietary nutrients [ 1, 2].
Malabsorption of nutrients follows the loss of absorptive surface, which may explain most of the symptoms of CD.
Based on the finding of an increased villus height:crypt depth ratio, it was assumed that the plant supplements rich in polyphenols might improve the digestibility of nutrients due to an increased absorptive surface of the intestine.
Villi become fused and broad, causing formation of leaves and ridges, which reduces the absorptive surface area of the gut and causes modest maldigestion and malabsorption of nutrients [ 6].
Not only do these episodes prevent the retention of nutrients from food, we now know that they permanently alter the absorptive capacity of a child's guts, by lessening the number of the villi on intestinal walls which are meant to trap nutrients.
In the third phase, long-term satiety is mainly determined by post-absorptive effects, such as metabolite concentrations in peripheral blood (insulin, glucose, amino acids) and oxidation of nutrients (thermogenesis) in liver and other metabolically active tissues.
