Norwegian processed foods in the prevention of colorectal cancer

The project investigates the association between consumption of processed meat (sausage) and colorectal cancer (CRC). Norway has the highest incidence of CRC in Europe, and in two Norwegian prospective studies frequent consumption of sausages was associated with increased risk of CRC. It is therefore an urgent need for more research that can identify potential underlying mechanisms, and at the same time find opportunities to make processed meat products healthier. Recently, there has been an increasing interest in using vegetables in meat products. More knowledge is needed about the health effects of such products, especially if the addition of vegetables can reduce the risk of CRC. The project aims to quantify potential carcinogenic compounds formed during heat treatment of sausages, and in the digestive tract using in vitro models. The carcinogenic potential (tumor development) is determined in a mouse model. Observed changes in the gut microflora are compared with analyses of the gut flora obtained from individuals participating in a Norwegian CRC screening program. By using advanced statistics, we hope to find associations between food ingredients, presence of carcinogenic compounds in the intestine, carcinogenic potential in mouse, and relevance to development of colorectal cancer in humans. So far, the project has provided increased insight into which ingredients in sausage that affect the formation of potentially carcinogenic compounds (malondialdehyde, hydroxyalkenals, nitrosamines, heterocyclic amines) during production, frying and digestion. Results show that the addition of selected vegetables to sausage may protect against the formation of harmful compounds. Addition of nitrite causes higher levels of nitrosamines but inhibits the formation of malondialdehyde. To study the effect of nitrite in more detail, experiments have been carried out with sausage added spinach which is naturally high in nitrate/nitrite. Also, the role of nitrite in saliva has been investigated. Furthermore, a study has been performed with a colon fermentation model indicating that nitrite and spinach added to sausage affect the gut flora and formation of beneficial short-chain fatty acids (SCFA) in colon. The mouse studies have not been finally completed, but so far there is no clear evidence of increased tumour development in mice fed with sausages. Preliminary results from the human study support previous findings showing an association between intake of red meat and early stages of CRC, while the association between sausage consumption and CRC is not as clear. Future analyses may tell whether the relationship between meat intake and CRC development is affected by the gut flora.

Prosjektet har bidratt til langsiktig kompetansebygging ved Nofima, NMBU, Kreftregisteret og DTU (Danmark), noe som er viktig for fremtidig forskning på nasjonalt og internasjonalt nivå. Prosjektet har vært tverrfaglig og bidratt til kunnskapsbygging innen flere fagfelt; kjøtt-teknologi, in vitro fordøyelse, in vitro fermentering (tarmflora), analyse av nitrosaminer i fordøyd materiale, kreftutvikling i mus, kjøtt og tarmkreft. Det er lagt et viktig grunnlag for videre forskning på de underliggende mekanismene for sammenhengen mellom inntak av bearbeidet kjøtt og risiko for tarmkreft, og prosjektet har resultert i ny kunnskap som kan benyttes av industrien til å lage sunnere kjøttfarseprodukter. Prosjektet har ikke kunnet dokumentere at norske pølser er kreftfremkallende med de modellene/metodene som er benyttet, og det er behov for videre forskning på hva det er i rødt kjøtt som kan bidra til utvikling av tarmkreft.

The project will investigate whether Norwegian raw materials and ingredients in processed meat (sausage) can affect development of colorectal cancer (CRC). The International Agency for Research on Cancer (2015) has classified consumption of processed meat as carcinogenic to humans, and in two Norwegian prospective studies frequent consumption of sausages was the only dietary factor associated with increased risk of CRC. Norway has the highest incidence of CRC in Europe, and it is therefore an urgent need for more research that can identify potential mechanisms linking Norwegian processed foods and CRC development. At the same time it is important to find opportunities to make processed meat products healthier. Recently, there has been an increasing interest in using vegetables in processed meat (e.g. meat balls and sausages). These are products where rest raw materials, both from vegetable- and meat production, can easily be included. More knowledge is needed about the health effects of such products, especially if the addition of vegetables to processed meat can reduce the risk of CRC. The project will quantify potential carcinogenic compounds formed during 1) heat treatment, 2) in vitro digestion and 3) in vitro gut fermentation of model products (sausage), and the carcinogenic potential will be determined in a mouse model. Observed changes in microbiota will be compared with analyses of microbiota obtained from individuals participating in a Norwegian CRC screening program. By using advanced statistics including multivariate modelling and multi-block analysis we hope to find associations between food ingredients, formation of carcinogenic compounds in the intestine, carcinogenic potential in mouse, and relevance to CRC development in humans.