Chemical and Nutritional Studies of Flaxseed (Variety Linott) in Rats.
Chemical and Nutritional Studies of Flaxseed (Variety Linott) in Rats.
Year: 1992
Authors: W M N Ratnayake, W A Behrens, P W F Fischer, M R L’Abbe, R Mongeau, J L Beare-Rogers.
Publication Name: J. Nutr. Biochem.
Publication Details: Volume 3; Page 232.
Abstract:
Flaxseed is becoming more common in the diet due to its high levels of ALA and lignans. However, ALA is highly unstable and may result in oxidative stress in tissues. flaxseed is also high in insoluble fiber, in particular phytate which is able to bind dietary minerals and reduce their absorption. In this study, the authors were interested in assessing the nutritional effects of high dietary levels of the flaxseed variety Linott in rats. The thermal stability of flaxseed exposed to accelerated heating was determined. Whole and coursely ground flaxseed was stored at room temperature for up to 44 weeks in order to determine storage stability. In the feeding trials, weanling rats were fed diets containing ground flaxseed at levels of 0, 10, 20 or 40% for 90 days. No differences were found in the food intake or in body and organ weights of animals fed all levels of flaxseed in comparison to animals fed no flaxseed. Serum TG, TC and LDL-C concentrations were significantly lower in the rats fed the 20% and 40% flaxseed diets compared to the 0% flaxseed group. HDL-C concentrations and LDL:HDL ratios were tended to be lower in the FS groups when compared to the 0% flaxseed group. However, significant reductions were noted only in the group fed 40% flaxseed. The incorporation of flaxseed in the diet caused significant elevations in the levels of ALA in adipose tissue and in organs. EPA, DPA and DHA levels were also higher in the heart and liver of flaxseed -fed rats when compared to the 0% flaxseed group. AA levels were reduced in the heart and liver of animals fed 40% flaxseed. A significant lowering of tissue vitamin E levels and an elevation of urinary thiobarbituric reacting substances occurred only in the 40% flaxseed group. Dietary fiber in the flaxseed consists of about 40% soluble and 60% insoluble fiber. Soluble fiber produces viscous properties in the intestine that can contribute to hypolipidemic effects. In this study, the fiber content of the flaxseed appeared to be largely fermentable and was associated with fecal bulking and a large increase in fecal moisture, comparable to that noted in previous studies for wheat bran. Phytate levels in the flaxseed diets had no effect on zinc status. The oil in both the intact and the ground flaxseed was found to be thermally and oxidatively stable. Based on the criteria assessed, the authors concluded that moderate intakes of flaxseed do not have adverse effects on mineral absorption or oxidative stress in rat tissues. The ALA in the flaxseed was stable, found to be bioavailable and to be converted to longer chain n-3 PUFAs. The authors indicated that flaxseed ALA and fiber may prove beneficial in reducing serum lipid levels in humans.
