Abstract
BACKGROUND Whether different intakes of vegetables and fruit modulate immunologic markers is currently not known. OBJECTIVE We investigated the effects of low, medium, and high intakes of vegetables and fruit on markers of immune functions, including nonspecific markers of inflammation. DESIGN In a randomized controlled trial, nonsmoking men consumed a diet that included < or = 2 servings/d of vegetables and fruit for 4 wk. The subjects were then randomly assigned to 1 of 3 groups to consume 2 servings/d, 5 servings/d, or 8 servings/d of carotenoid-rich vegetables and fruit for another 4-wk period. Plasma concentrations of vitamins C and E and carotenoids were measured. The assessment of immunologic and inflammatory markers included the number and activity of natural killer cells, secretion of cytokines, lymphocyte proliferation, and plasma C-reactive protein concentrations. RESULTS The high intake (8 servings/d) of vegetables and fruit significantly increased total carotenoid concentrations in plasma compared with the low intake (2 servings/d; week 4 compared with week 8), whereas concentrations of vitamins C and E did not differ between week 4 and week 8. Immunologic markers were not significantly modulated. In contrast, C-reactive protein was significantly reduced at week 8 in the subjects who consumed 8 servings/d of vegetables and fruit compared with those who consumed 2 servings/d. CONCLUSIONS In healthy, well-nourished, nonsmoking men, 4 wk of low or high intakes of carotenoid-rich vegetables and fruit did not affect markers of immune function. However, a high intake of vegetables and fruit may reduce inflammatory processes, as indicated by the reduction of plasma C-reactive protein.
