Consumption of thermally-oxidized sunflower oil by chicks reduces alpha-tocopherol status and increases susceptibility of tissues to lipid oxidation.

The effect of heated sunflower oil consumption on alpha-tocopherol status, fatty acid composition and oxidative stability of chicken tissues was investigated. Chicks were fed on diets containing (g/kg): fresh sunflower oil (FSO) 40, heated sunflower oil (HSO) 40 or heated sunflower oil (40) supplemented with alpha-tocopheryl acetate (HSE) to a similar alpha-tocopherol concentration as the FSO diet. Concentrations of alpha-tocopherol in tissues of chicks fed on HSO and HSE were significantly lower than those of chicks fed on FSO. Significant correlations were observed between plasma alpha-tocopherol concentration and the alpha-tocopherol concentrations of other tissues (r > or = 0.67, P < 0.005) and between log plasma alpha-tocopherol and plasma thiobarbituric acid-reacting substances (TBARS) concentrations (r -0.851, P < 0.001). The concentrations of TBARS in tissues of chicks fed on the various diets were generally very similar before stimulation of peroxidation with Fe-ascorbate. Susceptibility of tissues to Fe-ascorbate-induced lipid peroxidation was increased by feeding HSO. Supplementation with alpha-tocopheryl acetate reduced susceptibility to lipid oxidation to varying degrees, depending on the tissue. The results suggest that chronic ingestion of oxidized lipids may compromise free-radical-scavenging activity in vivo by depleting alpha-tocopherol in the gastrointestinal tract, or possibly in plasma and other tissues.