Modulation of plasma and tissue cholesterol and fatty acid composition by feeding flax and canola seeds and oils to rats

Abstract

Intact full-fat oil seeds might be more resistant to oxidation than extracted and refined oils and might therefore be used as sources of dietary fat. The present study was conducted to examine and compare the influence of feeding full-fat flax and canola seeds and oils on the plasma and tissue lipids of the rat. Male weanling Sprague Dawley rats (n = 4) were housed individually in metabolic cages and fed isoenergetic and isonitrogenous diets containing full-fat flax (FFF), flax meal + flax oil (FO), full-fat canola (FFC), canola meal + canola oil (CO), and soybean meal + animal tallow (AT). After 6 wk of feeding, plasma cholesterol levels were significantly (P < 0.05) reduced in rats fed flax diets (FF and FO) but not in those fed canola diets (FFC and CO). Liver cholesterol levels were not affected by dietary treatment. The highest levels of α-linolenic acid (LNA) and eicosapentaenoic acid (EPA) were recorded in the plasma, liver, heart and epididymal fat of rats fed the flax-containing diets. Intermediate levels of LNA and EPA in plasma and tissues were found in rats fed canola-containing diets. Rats fed flax diets had less arachidonic acid (AA) in plasma, liver, and heart tissues than those fed control and canola diets, indicating inhibition of AA synthesis by high dietary LNA provided by full-fat flax seed and flax oil. These results demonstrated that full-fat flax and canola seeds could be used as sources of dietary LNA to modify plasma and tissue lipids. Key words: Flax seed, canola seed, cholesterol, fatty acid, rat