Food viscosity as determinant for adaptive growth responses in rat intestine: long-term feeding of different hydroxyethyl celluloses

Carbohydrate gelling agents can be regarded as being representative for the soluble and viscous fractions of dietary fibre. Their dietary concentratio n affects the consistency of the ingested food as well as the dilution of n utrients and energy. By feeding hydroxyethyl cellulose (HEC) differing in m olecular mass, and thus in its viscosity properties, only the consistency o f the diet was modified. Three HEC (of low (LV), medium (MV) and high visco sity (HV)) were employed in a 6-week feeding study with female rats to eval uate the effect of the viscosity on adaptive responses of intestinal growth variables. Each of the HEC was added in three increasing concentrations (8 , 16, and 32 %, w/w) to a fibre-free control diet to yield nine test groups besides a fibre-free and an additional, fibre-rich, cereal-based control g roup. Except for the highest concentration of the high viscosity product (3 2 % HV-HEC), the dilution of the energy density of the diet was almost comp letely compensated by an increased food intake. With the same exception, en ergy utilisation was not impaired and, therefore, body-weight gains in the test groups were not significantly different from that in the control. Most other changes, e.g. increases in small intestinal length, mucosal DNA cont ent, caecal and colonic weight, not only depended on the dietary concentrat ion but also on the viscosity of HEC in a manner that either increasing the viscosity at a given dietary concentration or increasing the dietary conce ntration at a given viscosity led to the same results. These findings clear ly prove the important role of the viscosity of the lumen content, as a mer e physico-chemical factor, in determining adaptative growth responses in th e intestinal tract of rats.