Journal Article

Green vegetables, red meat and colon cancer: chlorophyll prevents the cytotoxic and hyperproliferative effects of haem in rat colon

Johan de Vogel, Denise S.M.L. Jonker-Termont, Esther M.M. van Lieshout, Martijn B. Katan and Roelof van der Meer

in Carcinogenesis

Volume 26, issue 2, pages 387-393
Published in print February 2005 | ISSN: 0143-3334
Published online February 2005 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgh331
Green vegetables, red meat and colon cancer: chlorophyll prevents the cytotoxic and hyperproliferative effects of haem in rat colon

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Diets high in red meat and low in green vegetables are associated with increased colon cancer risk. This association might be partly due to the haem content of red meat. In rats, dietary haem is metabolized in the gut to a cytotoxic factor that increases colonic cytotoxicity and epithelial proliferation. Green vegetables contain chlorophyll, a magnesium porphyrin structurally analogous to haem. We studied whether green vegetables inhibit the unfavourable colonic effects of haem. First, rats were fed a purified control diet or purified diets supplemented with 0.5 mmol haem/kg, spinach (chlorophyll concentration 1.2 mmol/kg) or haem plus spinach (n = 8/group) for 14 days. In a second experiment we also studied a group that received haem plus purified chlorophyll (1.2 mmol/kg). Cytotoxicity of faecal water was determined with a bioassay and colonic epithelial cell proliferation was quantified in vivo by [methyl-3H]thymidine incorporation into newly synthesized DNA. Exfoliation of colonocytes was measured as the amount of rat DNA in faeces. In both studies haem increased cytotoxicity of the colonic contents ∼8-fold and proliferation of the colonocytes almost 2-fold. Spinach or an equimolar amount of chlorophyll supplement in the haem diet inhibited these haem effects completely. Haem clearly inhibited exfoliation of colonocytes, an effect counteracted by spinach and chlorophyll. Finally, size exclusion chromatography showed that chlorophyll prevented formation of the cytotoxic haem metabolite. We conclude that green vegetables may decrease colon cancer risk because chlorophyll prevents the detrimental, cytotoxic and hyperproliferative colonic effects of dietary haem.

Keywords: ANOVA, one-way analysis of variance; ICP-AES, inductive coupled plasma absorption emission spectrophotometer

Journal Article.  5702 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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