a1 Chair of the Biofunctionality of Food, Department of Food and Nutrition, Technical University of Munich, Hochfeldweg 1, 85350 Freising, Germany
a2 Institute of Nutritional Physiology, Federal Research Centre for Nutrition and Food, Karlsruhe, Haid-und-Neustraße 9, 76131 Karlsruhe, Germany
a3 Institute for Nutrition, Department of Nutritional Toxicology, Friedrich-Schiller-University, Dornburgerstraße 25, 07743 Jena, Germany
High intakes of carotenoid-rich fruits and vegetables are associated with a reduced risk of various cancers including colon cancer. A human intervention study with carrot and tomato juice should show whether a diet rich in carotenoids, especially high in β-carotene and lycopene, can modify luminal processes relevant to colon carcinogenesis. In a randomised cross-over trial, twenty-two healthy young men on a low-carotenoid diet consumed 330 ml tomato or carrot juice per d for 2 weeks. Intervention periods were preceded by 2-week depletion phases. At the end of each study period, faeces of twelve volunteers were collected for chemical analyses and use in cell-culture systems. Consumption of carrot juice led to a marked increase of β-carotene and α-carotene in faeces and faecal water, as did lycopene after consumption of tomato juice. In the succeeding depletion phases, carotenoid contents in faeces and faecal water returned to their initial values. Faecal water showed high dose-dependent cytotoxic and anti-proliferative effects on colon adenocarcinoma cells (HT29). These effects were not markedly changed by carrot and tomato juice consumption. Neither bile acid concentrations nor activities of the bacterial enzymes β-glucosidase and β-glucuronidase in faecal water changed after carrot and tomato juice consumption. Faecal water pH decreased only after carrot juice consumption. SCFA were probably not responsible for this effect, as SCFA concentrations and profiles did not change significantly. In summary, in the present study, 2-week interventions with carotenoid-rich juices led only to minor changes in investigated luminal biomarkers relevant to colon carcinogenesis.
(Received February 09 2007)
(Revised July 02 2007)
(Accepted July 24 2007)
Abbreviations: EC25, effective concentration at 25 % reduction of cell viability; IC50, half-maximal growth inhibitory concentration; MTT, 3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyltetrazolium bromide