PLASMA CAROTENOIDS AS BIOMARKERS OF VEGETABLE INTAKE - THE UNIVERSITY-OF-MINNESOTA CANCER PREVENTION RESEARCH UNIT FEEDING STUDIES

High vegetable intake has been associated with a decreased risk for va rious human cancers in epidemiological studies, Carotenoids are plant compounds that may both possess chemopreventive activity and be useful biomarkers of vegetable and fruit intake, Nineteen men and women were randomized into a controlled crossover feeding study to measure the e ffect of vegetable intake on plasma carotenoid concentrations, Partici pants consumed each of 4 experimental diets for 9 days, The control di et consisted of commonly consumed foods and was essentially carotenoid free. High vegetable diets (carotenoid, cruciferous, and soy) consist ed of the control diet plus carrots and spinach (carotenoid), broccoli and cauliflower (cruciferous), and tofu and FriChik (soy), Plasma car otenoid concentrations were highest on the carotenoid and cruciferous diets, When compared to the control, mean plasma alpha-carotene, beta- carotene, and lutein concentrations were 5.2, 3.3, and 2.2 times highe r on the carotenoid diet, respectively (P < 0.001), Mean plasma lutein concentrations were 2.1 times higher on the cruciferous versus the co ntrol diet (P < 0.001), There were no differences between diets in pla sma beta-cryptoxanthin and lycopene concentrations, These data indicat e that plasma alpha-carotene, beta-carotene, and lutein may be useful biomarkers of carotenoid-rich food intake and that lutein may act as a n intake biomarker of commonly consumed vegetables in the Cruciferae f amily, These findings should prove useful in undertaking dietary inter vention trials because they suggest the feasibility of monitoring inta ke of some plant foods and of distinguishing among plant food groups.