Plasma concentrations of carotenoids in healthy volunteers after intervention with carotenoid-rich foods

Aim of the study: The present study was conducted to investigate changes in the plasma concentration of carotenoids and carotenoid oxidation products, vitamin A, alpha- and gamma-tocopherol, and ubiquinone-10 during a dietary intervention trial with 23 male healthy volunteers. Method: A two week carotenoid depletion period was followed by a daily cons umption of 330 mt tomato juice (40 mg lycopene), then by 330 mt carrot juic e (15.7 mg alpha-carotene and 22.3 mg beta-carotene), and then by a 10 g sp inach powder preparation (11.3 mg lutein and 3.1 mg beta-carotene) served w ith main meals for two weeks, respectively. Blood samples were collected in the morning after an overnight fasting and carotenoids, vitamin A, tocophe rols, and ubichinone were analyzed by reversed-phase HPLC. Results: During the tomato juice intervention, plasma concentrations of tra ns- and cis-lycopene increased 3-fold compared to the depletion period. Lyc opene oxidation products could be demonstrated in plasma and were significa ntly elevated compared to control (p < 0.001). After two weeks of carrot ju ice consumption, alpha-carotene and beta-carotene concentrations increased 8.6- and 3.2-fold, respectively. Finally, during the spinach consumption pe riod the lutein concentration increased 2-fold, while the beta-carotene con centrations were still elevated 2-fold. Conclusions: The moderate change in dietary habits, e.g., the consumption o f 330 mt of carotenoid-rich vegetable juices caused significant changes in the plasma carotenoid concentrations, indicating a high bioavailability of carotenoids from these processed vegetable products. The changes in plasma carotenoid concentrations reflected the carotenoid composition of the consu med foods. However, particularly during the tomato juice intervention perio d the occurrence of lycopene oxidation products and cis-lycopene isomers in plasma was eminent. The formation may be due to antioxidant reactions of l ycopene in the organism.