Linseed Dietary Fibers Reduce Apparent Digestibility of Energy and Fat and Weight Gain in Growing Rats

Key Findings

Dietary fiber in flaxseed is characterized by neutral arabinoxylans and highly acidic rhamnose containing polysaccharides on the outside of the seed coat (the mucilage). When hydrated these form highly viscous solutions. In this study, a fiber derived from the mucilage fraction of flaxseed lowered daily weight gain in rats. Apparent fat and energy digestibility were decreased by 10 percent to 20 percent. Additionally, fecal volume and energy excretion significantly increased with the flax fiber diet. No differences in body weight gain despite differences in apparent fat and energy digestibility. Human intervention trials are required to confirm the energy reduction properties of flaxseed fiber.

ABSTRACT

Dietary fibers (DF) may affect energy balance, an effect often ascribed to the viscous nature of some water soluble DF, which affect luminal viscosity and thus multiple physiological processes. We have tested the hypothesis that viscous linseed DF reduce apparent nutrient digestibility, and limit weight gain, in a randomized feeding trial where 60 male, growing, Wistar rats, with an initial weight of about 200 g, were fed different diets (n equals 10 per group) to low DF control (C), 5 percent DF from cellulose (5 CEL), CEL plus 5 percent DF from whole (5 WL) or ground linseed (5 GL), CEL plus 5 percent DF from linseed DF extract (5 LDF), and CEL plus 10 percent DF from linseed DF extract (10 LDF). Diets were provided ad libitum for 21 days. Feed intake and faecal output were measured during days 17 to 21. Faecal fat excretion increased with increasing DF content and was highest in the 10 minus LDF group. Apparent fat digestibility was highest with the C diet (94.9 percent 0.8 percent) and lowest (74.3 percent 0.6 percent) with the 10 LDF diet, and decreased in a non linear manner with increasing DF. Apparent fat digestibility also decreased with increased accessibility of DF (5 WL vs. 5 GL) and when the proportion of viscous DF increased (5 GL vs. 5 LDF). The 10 LDF resulted in a lower final body weight (258 plus minus 6.2 g) compared to C (282 plus minus 5.9 g), 5 CEL (281 plus minus 5.9 g), and 5 WL (285 plus minus 5.9 g). The 10 LDF diet reduced body fat compared to 5 CEL. In conclusion, DF extracted from linseed reduced apparent energy and fat digestibility and resulted in restriction of body weight gain in growing rats. (Authors abstract)

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