Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil

Abstract

Objective: To determine whether consumption of five portions of fruit and vegetables per day reduces the enhancement of oxidative stress induced by consumption of fish oil. Subjects: A total of 18 free-living healthy smoking volunteers, aged 18-63 y, were recruited by posters and e-mail in The University of Reading, and by leaflets in local shops. Design: A prospective study. Setting: Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, Whiteknights PO Box 226, Reading RG6 6AP, UK. Intervention: All subjects consumed a daily supplement of 4 Â 1 g fish oil capsules for 9 weeks. After 3 weeks, they consumed an additional five portions of fruits and vegetables per day, and then they returned to their normal diet for the last 3 weeks of the study. Fasting blood samples were taken at the ends of weeks 0, 3, 6 and 9. Results: The plasma concentrations of ascorbic acid, lutein, b-cryptoxanthin, a-carotene and b-carotene all significantly increased when fruit and vegetable intake was enhanced (Po0.05). Plasma concentrations of a-tocopherol, retinol and uric acid did not change significantly during the period of increased fruit and vegetable consumption. Plasma oxidative stability, assessed by the oxygen radical absorbance capacity (ORAC) assay, also increased from weeks 3-6 (Po0.001) but not in association with increases in measured antioxidants. Lag phase before oxidation of low-density lipoprotein (LDL) significantly decreased in the first 3 weeks of the study, reflecting the incorporation of EPA and DHA into LDL (Po0.0001). Subsequent enhanced fruit and vegetable consumption significantly reduced the susceptibility of LDL to oxidation (Po0.005). Conclusion: Fish oil reduced the oxidative stability of plasma and LDL, but the effects were partially offset by the increased consumption of fruit and vegetables.

Effects of vitamin E on the toxicity of oxidized LDL on endothelial cells in vitro in smokers vs nonsmokers on diets rich in fish

“…Also some but not all other studies have reported that intake of n-3 fatty acids promote increased peroxidation of LDL (Pedersen et al, 2003;Piolot et al, 2003;Roberts et al, 2003). In the present study, the rate of LDL oxidation was significantly higher in nonsmokers than in smokers, whereas the lag phase of LDL oxidation did not differ significantly between the groups at baseline.…”

“…Ex vivo measures of LDL resistance to oxidation have shown significant increases even at low doses of alpha-tocopherol (43-200 mg/day) (Princen et al, 1995;Maskarinec et al, 1999;Upritchard et al, 2003). Antioxidant supplementation or increased consumption of fruit and vegetables has been reported to reduce the susceptibility of LDL to oxidation also in smokers (Princen et al, 1992;Roberts et al, 2003). In fact, beneficial effects of vitamin E supplementation on atherosclerosis may be the most relevant to persons with initially low serum levels of vitamin E. In this study, the lag phase of LDL oxidation prolonged significantly in both the study groups, smokers and nonsmokers after 8 weeks supplementation of vitamin E. Moreover, the effect of vitamin E was greater in smokers than in nonsmokers, which has also been reported by Salonen et al (2003).…”

“…Size and fatty acid composition of low density lipoprotein (LDL) affect the oxidation capacity (Esterbauer et al, 1992). Most reports suggest that intake of n-3 fatty acids promote increased peroxidation of LDL in vitro and in vivo (Korpela et al, 1999;Pedersen et al, 2003;Roberts et al, 2003). However, it has also been reported on unaltered peroxidation with dietary intake of n-3 fatty acids (Piolot et al, 2003).…”

Including Walnuts in a Low-Fat/Modified-Fat Diet Improves HDL Cholesterol-to-Total Cholesterol Ratios in Patients With Type 2 Diabetes

“…The increase in dietary PUFA, however, has been a concern for antioxidant status in diabetes (12), but blood levels of antioxidants in people with diabetes appear related to serum lipids, not dietary intake, with products of oxidative damage more linked to intakes of SFA and cholesterol and to levels of endogenous antioxidants (44). In the case of large doses of fish oil supplements, a decreased oxidative stability of plasma and LDL has been demonstrated in healthy subjects, but this was offset by including five portions of fruit and vegetables in the daily diet (45). In our study, SFA intakes were kept low, and five portions of fruits and vegetables were included in the dietary advice.…”

Vitamin E as an Antioxidant : E Vi̇tami̇ni̇ni̇n Anti̇oksi̇dan Rolü

“…The antioxidant efficiency of vitamin E appears to be greatly enhanced by regeneration of the vitamin from its oxidised products (143). Appreciation of other antioxidants (144)(145)(146) has developed the notion that while vitamin E protects lipids other antioxidants must recycle vitamin E. The other major antioxidants are coenzyme Q and vitamin C (147,148) Regeneration of a-tocopherol from its tocoperoxyl radical have been demonstrated by vitamin Another explanation for the low levels of cc-TQ in tissues is that the tocopherol may be one of the last antioxidant substances to be consumed during oxidative stress. Burton and Ingold, found that other antioxidants such as sulphydryl groups in proteins were found to be used preferentially to tocopherols during oxidations initiated by free radicals in human plasma (28,153).…”