What study suggested that unabsorbed dietary iron is the cause of colorectal cancer?

Another study supports these findings from Kato of unabsorbed dietary iron and a possible association with colorectal cancer. The study included 18 healthy volunteers who supplemented their diet with 100mg of iron sulfate. The subjects documented their food intake and samples of feces were taken in advance, during and after the two weeks of supplementation. The results showed that levels of iron in the faeces significantly increased during the two weeks of supplementation and restored to starting levels after the supplementation stopped. The concentration of weakly bound iron started at 60 μmol/L before supplementation and increased to 300 μmol/L during the supplementation. This increase shows a higher amount of unabsorbed iron was concentrated into the faeces. During the two weeks of supplementation, it was recorded the production of free radicals had greatly increased. This increase in free radical production suggests it could increase colorectal cancer risk, as free radicals can cause cell damage which may initiate cancer development. This evidence suggests unabsorbed dietary iron causes an increase in free radical production in the large intestine which may lead to damage of mucosal cells and an increase in the carcinogen production.

In conclusion, iron intake and risk of colorectal carcinoma is a controversial topic. There is a lot of evidence from experimental and epidemiologic studies which suggest a positive association between body iron stores and dietary iron and the pathogenesis of colorectal cancer or adenomas.

In controversy, despite there only being few, other studies suggest there is no or little association between dietary iron intake or body iron levels, and that serum ferritin concentration is not associated with the recurring colorectal adenomas – which can be pre-cancerous.