The purpose of the present study was to determine the effects of dietary antioxidant restriction on plasma concentrations of carotenoids and inflammatory markers at rest and in response to exercise in endurance-trained males. Seventeen males performed two exercise trials 2 weeks apart. Participants followed their habitual antioxidant diet (H-AO) before the first exercise test, then a restricted antioxidant diet (R-AO) for 2 weeks before the second exercise test. Blood was collected pre- and post-exercise. Dietary intakes of fibre, ascorbic acid and β-carotene were lower (P < 0·05) on the R-AO diet, but no other differences were observed. Pre-exercise plasma β-carotene concentrations were lower (H-AO, 195 (sd 92); R-AO, 123 (sd 54) ng/ml; P < 0·05), and TNF-α concentrations were higher (H-AO, 16 (sd 7); R-AO, 613 (sd 325) pg/ml; P < 0·01) on the R-AO diet compared to the H-AO diet. Most plasma carotenoid concentrations decreased with exercise, but this effect was more consistent on the H-AO diet. No differences in plasma IL-6 concentrations were observed pre-exercise, whereas post-exercise plasma IL-6 concentrations (H-AO, 30·3 (sd 16); R-AO, 15·3 (sd 5) pg/ml; P < 0·05) were lower following the R-AO diet. Post-exercise TNF-α concentrations were higher on the R-AO diet. Ratings of perceived effort during submaximal exercise were higher (P < 0·05) on the R-AO diet, but there was no difference in the time to exhaustion between diets. In conclusion, lower dietary intakes of carotenoids alter the plasma concentrations of antioxidants and markers of inflammation at rest and in response to exercise.
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