Effects of Introducing Linseed in Livestock Diet on Blood Fatty Acid Composition of Consumers of Animal Products

January 1, 2002 Human Health and Nutrition Data 0 Comments

Effects of Introducing Linseed in Livestock Diet on Blood Fatty Acid Composition of Consumers of Animal Products

Year: 2002
Authors: Weill, P Schmitt, B. Chesneau, G. .Daniel, N. Safraoub, F. Legrand, P.
Publication Name: Ann. Nutr. Metab.
Publication Details: Volume 46; Pages 182 – 191.


Reducing the ratio between essential fatty acids C18:2 n�6/C18:3 n�3 down to 5 is recommended by Nutritional Guidelines. We studied the fatty acid (FA) changes in consumers� plasma following changes in livestock diet. First, a zootechnical study introduced 5% of extruded linseed into the diet of livestock to replace other oleaginous ingredients, and on an iso-nutritional values basis. The products from linseed-fed animals contained more n�3 fatty acids (precursor a�-linolenic and derivatives obtained by elongations and desaturations) than control animal products (issued from animals fed without linseed), and more conjugated linoleic acids (CLA). The n�6/n�3 ratio was reduced by 54% in butter, 60% in meat and 86% in eggs. Following this, a double-blind, randomised, cross-over clinical study involving 75 healthy volunteers compared plasma and erythrocyte FA profiles in consumers of animal products (from livestock fed the linseed diet or from livestock fed standard diet). It showed modifications in the FA composition of the experimental human regimen with more C18:3 n�3 (1.65 vs. 0.75 g/day), and more n�3 derivatives. The C18:2 n�6/C18:3 n�3 ratio decreased (7 vs. 15). In volunteers� plasma, C18:3 n�3 increased in the essay group (0.93 vs. 0.44% of the FA), so did n�3 derivatives and CLA. The n�6/n�3 ratio decreased from 14.3 to 10.2. In erythrocytes, C20:5 n�3 increased in the essay group (0.59 vs. 0.45%) and so did C22:6 n�3. The n�6/n�3 ratio decreased in parallel from 4.2 to 3.8. Without any changes in consumers� eating habits, foodstuffs from animals fed linseed diets induced significant modifications of human plasma and erythrocyte fatty acid composition (comparable to that noted under the �Cretan� diet) and a sharp increase in CLA. (Author`s abstract)
This study tested the following hypotheses: (1) that an exclusive plant modification of livestock feeding by using linseed (flaxseed) induces changes in the fatty acid contents of foodstuffs of animal origin by increasing n�3 (precursor and very-long-chain derivatives) fatty acids, and (2) that human consumption of these foods improves fatty acid composition and thus could constitute an effective measure of CVD prevention without the need to radically change previous nutritional habits. Animal fats constitute about half of all human nutritional lipid intake in developed countries and lipid profiles vary according to the diets given to the livestock. Modern husbandry methods have considerably reduced ALA availability in animal products. In this study, deterioration in animal product quality as a result of feeing a high level of ALA was not reported. In linseed-fed animals less palmitic acid and more stearic acid in products were noted. Less C18:1 n�9 in all the linseed-fed animal products, except in milk was seen. Linseed fed ruminant products were richer in C18:1 trans11 (vaccenic acid) and in CLA cis9 trans11 (rumenic acid), two FA produced from ALA after the isomerisation-hydrogenation occurring in the rumen. Introducing extruded linseed in animal diets increased the ALA content of the products. The sera levels of ALA (respectively, 0.93 and 0.90% of the total FA in �full-dose essay� and �half-dose essay� groups) were high in comparison with other studies at same ALA ingestion level from rapeseed or linseed oil. Similarly, the increases in blood red cell levels in C20:5 n�3,  C22:5 n�3, C22:6 n�3 (mainly in phospholipids) are markedly higher than those observed after introduction of ALA from plant oils. The authors did not offer reasons to explain the high availability of animal sources of n�3 FA, but proposed: (i) the origin and composition of n�3 FA (coming from various products) provide all the n�3 FA together and at the different meals; (ii) the relatively low amount of n�3 FA avoid their use as energetic substrate, whereas SFAs are a preferential source for �-oxydation; (iii) the phospholipids constitute an important part of animal lipids (mostly in eggs and meat) and when present in the regimen, they ensure an efficient supply form of very-long-chain  FA. A significant �a-linolenic acid desaturation and elongation process appears to occur in animals. In human sera from the �essay� groups, the increase in n�3 FA (including n�3 long chain FA) was accompanied by a decrease in n�6 long-chain FA (especially C20:4 n�6). The authors conclude that  the introduction of extruded linseed in animal diets can provide a new and complementary way of ALA enrichment in human regimens. This n�3 FA enrichment procedure may be especially significant for consumers who usually eat animal fats. (Editor`s comments)

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