Many studies have made a connection between diets that are high in carbohydrates with an increased rate of colorectal cancer particularly in relatives of people that have had colorectal cancer but no definite mechanism for the relationship has been established until now. Alberto Martin of the University of Toronto and a team of collaborators are the first to define a metabolic pathway that links colorectal cancer and carbohydrate consumption in mice. The study was reported in the July 17, 2014, edition of the journal Cell.
Diets high in carbohydrates are known to interfere with the tumor suppression activity of a gene called the adenomatous polyposis coli gene (APC). This gene is thought to prevent colorectal cancers from being able to grow. A high-carbohydrate diet is also thought to interfere with the DNA repair function of the DNA mismatch repair protein gene (MSH2). The researchers considered mutations in both of these genes might be the connection between colorectal cancer and a diet that is high in carbohydrates.
The researchers tested their theories using mice that had been genetically altered to have mutations in the APC gene and the MSH2 gene. The test mice were genetically bred to have a predisposition to colorectal cancer. A low-carbohydrate diet or treatment with antibiotics was found to produce lower levels of the development of tumors in the test mice and reduce the rate of growth of existing colorectal tumors. The same treatments reduced the number of bacteria that produce a fatty acid called butyrate. High levels of butyrate produced an increase in the number of colorectal tumors in the test mice.
This is the first chemical correlation between a diet high in carbohydrates and a genetic mutation that increases the probability of developing colorectal cancer. The researchers note that the simplicity of the application in humans could be taking a particular antibiotic. The other option is eating fewer carbohydrates. The specifics of any treatment for people have not been worked out in full or tested yet but this discovery does offer significant hope for the 50,000 people that die from colorectal cancer annually in the United States.