Replacement of nitrite in meat products by natural bioactive compounds results in reduced exposure to N-nitroso compounds: the PHYTOME project

It has been proposed that endogenously formed N-nitroso compounds (NOCs) are partly responsible for the link between red meat consumption and colorectal cancer (CRC) risk. As nitrite has been indicated as one of the critical factors in the formation of endogenous NOCs, it is of high importance to replace or reduce the nitrite levels in meat. Therefore, the PHYTOME project was initiated (Phytochemicals to reduce nitrite in meat products; www.phytome.eu), an EU funded research project aiming to develop innovative meat products in which the food additive sodium nitrite (E251) has been replaced by natural compounds originating from fruits and vegetables. A human dietary intervention study was conducted in which healthy subjects consumed 300 grams of meat for two weeks, in subsequent order: normal processed red meat, white meat, and red processed meat with standard or reduced levels of nitrite and added phytochemicals. Consumption of standard-nitrite PHYTOME meat products leads to a significant reduction in Apparent Total N-nitroso Compounds (ATNC) levels in faecal water, a surrogate marker of endogenously formed NOCs, as compared to the consumption of conventional processed red meat products. A reduction of nitrite in the PHYTOME meat lowered these levels even further. In addition, DNA strand breaks induced in ex-vivo faecal water exposed Caco-2 cells and O6-methyl-guanine adducts levels in colonic DNA were significantly higher after consumption of normal processed red meat as compared to white meat intake. PHYTOME meat intake resulted in reduced levels of these genotoxic markers, however, these were not statistically significant. Whole genome gene expression analyses in colonic tissue identified differentially expressed genes and genes associated with ATNC, which are related to molecular pathways which may explain cancer risk initiation after intake of processed red meat and cancer risk prevention after intake of the PHYTOME meat. Together these results indicate that addition of natural extracts to conventional processed red meat products results in reduced endogenous formation of NOCs, and may therefore contribute to a reduced risk of CRC, which is mechanistically supported by gene expression analyses. The human dietary intervention study has a parallel design. There are 2 study groups (1 and 2), and in each study group there are 2 meat intervention periods (A and B), separated by a wash-out period (O). During intervention period “A”, participants were asked to consume the provided red processed meat products (red processed meat group), while in period “B” red processed meat products enriched with natural compounds were provided. For study group 1, the meat products of both period ”A” and “B” had standard nitrite levels (standard nitrite PHYTOME meat), while in study group 2 the nitrite levels in period “B” were reduced (reduced nitrite PHYTOME meat). At the beginning of the study and after each intervention period of 2 weeks, colonic biopsies were collected during an endoscopic examination and analysed for gene expression changes.