Impact of diets with corn oil or olive/sunflower oils on DNA damage in healthy young men

Summary

Background: Plant fats and oils are major sources of mono- and polyunsaturated fatty acids as well as vitamin E, the major fat-soluble antioxidants in human nutrition. Dietary antioxidants are expected to reduce cancer risk by minimizing DNA damage.

Aim of the study: To compare the effects of γ-tocopherol rich corn oil and the mixture of the α-tocopherol rich olive/sunflower oil on plasma concentration of tocopherols and on the frequency of sister chromatid exchange (SCE), an indicator of DNA damage.

Methods: This study had a double-blind, cross-over design and was conducted in 20 normal healthy non-smoking males aged 19–31 years. Design included a 2-week adjustment period and two 2-week test periods in which diets containing 30% energy as fat including either 80 g of corn oil (CO) (20 mg α-tocopherol, 100 mg γtocopherol) or 80 g of olive/sunflower oil (OSO) (24 mg α-tocopherol, 2.4 mg γ-tocopherol) as the main fat-source, were given. Blood samples for analysis of SCE rate and content of tocopherols were collected at the beginning (T0), after adjustment (T1) and after the test period (T2) in intervals of 2 weeks.

Results: After two weeks of the corn oil diet, the plasma concentration of γ-tocopherol increased but α-tocopherol decreased significantly compared to the olive/sunflower oil diet. The concentration of α-tocopherol increased (CO: 22.99 ± 1.11 vs. OSO: 24.40 ± 1.49 μmol/l) and that of γ-tocopherol decreased (CO: 4.19 ± 0.29 vs. OSO: 2.99 ± 0.25 μmol/l) after the olive/sunflower oil diet. Intake of the corn oil diet was associated with reduced SCE rate and intensity, whereas there was no change in SCE after the olive/sunflower oil diet (CO: 7.66 ± 0.25 vs. OSO: 8.06 ± 0.47 mean SCE/cell).

Conclusions: The combination of γ-tocopherol with α-tocopherol in corn oil diet despite the lower α-tocopherol equivalents/diene acid equivalents ratio achieved better protection against DNA damage than α-tocopherol alone in the olive/sunflower oil diet.