The Link Between Vegetables and Colon Cancer

By September 5, 2018 health, diet
Could a diet rich in green vegetables help prevent colon cancer?
Chemicals produced by vegetables such as kale, cabbage and broccoli could help to maintain a healthy gut and prevent colon cancer, a recent study from the Francis Crick Institute shows.  The study, published in Immunity, shows that mice fed on a diet rich in indole-3-carbinol (I3C) were protected from gut inflammation and colon cancer. Indole-3-carbinol is produced during the digestion of vegetables from the Brassica genus in the mustard family.  I3C is believed to prevent colon inflammation and cancer by activating a protein called the aryl hydrocarbon receptor (AhR).
The protein AhR signals immune cells and epithelial cells in the gut to activate in order to protect us from inflammatory responses to bacteria that live in the gut.  In the study, genetically modified mice that could not produce or activate AhR in their guts readily developed gut inflammation which progressed to colon cancer. 
When those same mice were fed them a diet enriched with I3C, they did not develop inflammation or cancer.  In addition, mice with developing cancer were switched to the I3C-enriched diet, and they had significantly less tumors which were also more benign.  These results hint at the ability of I3C to play a key role in activating AhR, which in turn appears to have a preventative effect on gut inflammation and colon cancer.
The addition of dietary I3C also had a surprising effect on unmodified mice with normal AhR expression.  Normal mice fed on standard or I3C-enriched food did not develop tumours during the study, mice fed a “purified control diet” developed colon tumours within 10 weeks.  Purified control diets are exact mixtures of carbohydrates, proteins, fats and fibres with vitamins and minerals. However, these diets contain less AhR-promoting chemicals than I3C-enriched diets.

The researchers discovered that AhR repairs damaged epithelial cells. Without the reparative effect of AhR, intestinal stem cells fail to differentiate, instead dividing uncontrollably which can ultimately lead to colon cancer.

“The profound effect of diet on gut inflammation and colon cancer was very striking,” -Dr Gitta Stockinger, Group Leader at the Francis Crick Institute

The good news is that many vegetables produce chemicals that keep AhR levels active in the intestine, potentially restoring epithelial cell differentiation and offering resistance to intestinal infections and colon cancer.  The effect of AhR is important, but genetic factors are also an important consideration that predispose individuals to colon cancer.  Although AhR cannot eliminate the genetic factors, those risks can be lessened by the protective nature of AhR.  Th research also suggests that even without genetic risk factors, a diet missing vegetables can lead to colon cancer.

Although the reseacrh is preliminary, with more studies planned, the link between increased consumption of vegetables and a lowered risk of inflammation and colon cancer is compelling.  As scientists uncover the mechanisms responsible for the lowered risk, perhaps drugs targeting those pathways can be developed that are effective at reducing the incidence of colon cancer.  In the meantime, dish up an extra serving of those leafy greens-according to science, it can’t hurt.