Antioxidative Power of Plant Oils in Humans: The Influence of α- and γ-Tocopherol

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Abstract
Background: The daily diet is usually comprised of a varying antioxidant and fatty acid content acquired from plant oils. The present study was performed to evaluate the antioxidative effects of a plant oil mixture rich in α-tocopherol (olive/sunflower oil) in comparison with a single γ-tocopherol-rich corn oil used in a normal, balanced human diet. Methods: In the context of a double-blind study 28 healthy nonsmoking male volunteers aged between 19 and 31 years were investigated. After 2 weeks of adjustment on a mixed, balanced diet (average 11.6 MJ, average fat intake ∼105 g/day), a 2-week test period with a diet of 80 g corn oil (CO)/day vs. a mixture of 68 g olive and 12 g sunflower oil/day (MO; total 80 g) as the main fat source, was followed by a crossover after 2 weeks. Blood samples were collected at the beginning of the study and at 2-week intervals. Results: The main carriers of tocopherol in blood are low-density lipoproteins (LDLs). A highly significant correlation (r2 = 0.73, p < 0.001) was found between plasma and LDL γ-tocopherol concentrations in the CO group, and a significant correlation was found between plasma and LDL α-tocopherol concentrations only in the MO group. Plasma and LDL total antioxidative capacity values could only be improved insignificantly in both groups to comparable extents, although the MO group had a twofold higher α-tocopherol equivalent/diene equivalent ratio (1.13 mg/g) than the CO group (0.55 mg/g). Conclusion: In spite of the higher P/S ratio (CO 4.2 vs. MO 1.2) and lower α-tocopherol equivalent/diene equivalent ratio, the antioxidant potential of CO in vivo (total antioxidative capacity in plasma and LDL) was as efficient as the MO. This positive finding might be explained by a synergism between α- and γ-tocopherol in the CO diet.

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