Vegetables matter: Kale, cabbage and broccoli linked to reduced risk of colon cancer, study finds

21 Aug 2018 --- Chemicals produced by vegetables such as kale, cabbage and broccoli could help to maintain a healthy gut and prevent colon cancer, a new study from the Francis Crick Institute has found. The research, published in Immunity, shows that mice fed on a diet rich in indole-3-carbinol (I3C) – which is produced when we digest cruciferous vegetables – were protected from gut inflammation and colon cancer. While the benefits of eating vegetables are well known, so far, many of the underlying mechanisms remained elusive.

“The results were surprising in the sense that we did not know the underlying mechanisms of our findings. We had no idea that this particular environmental factor [eating cabbage, kale and broccoli] would have such an impact on stem cells in the gut,” Dr. Gitta Stockinger, senior author and Group Leader at the Francis Crick Institute tells NutritionInsight.

The study identified that how I3C activates a protein called aryl hydrocarbon receptor (AhR) which can prevent colon inflammation and cancer.

“We often think of colon cancer as a disease promoted by a Western diet rich in fat and poor in vegetable content and our results suggest a mechanism behind this observation. Many vegetables produce chemicals that keep AhR stimulated in the gut,” adds Stockinger.

AhR acts as an environmental sensor, passing signals to immune cells and epithelial cells in the gut lining to protect us from inflammatory responses to the many bacteria that live in the gut.

“We studied genetically modified mice that cannot produce or activate AhR in their guts and found that they readily developed gut inflammation which progressed to colon cancer,” says first author Dr. Amina Metidji, from the Francis Crick Institute. “However, when we fed them a diet enriched with I3C, they did not develop inflammation or cancer. Interestingly, when mice whose cancer was already developing were switched to the I3C-enriched diet, they ended up with significantly fewer tumors which were also more benign.”

By studying both mice and mouse gut organoids – “mini guts” made from stem cells – the researchers found that AhR is vital for repairing damaged epithelial cells.

“Normal mice on the purified control diet developed colon tumors within 10 weeks, whereas mice on the standard chow didn’t develop any,” says co-corresponding author Dr. Chris Schiering, who worked on the study at the Crick and now works at Imperial College London. “This suggests that even without genetic risk factors, a diet devoid of vegetable matter can lead to colon cancer.”

Next steps?
Stockinger explains that the results hold promise as they indicate the importance of environmental factors. “While we can’t change the genetic factors that increase our risk of cancer, we can probably mitigate these risks by adopting an appropriate diet with plenty of vegetables.”

The team are now investigating whether the effects will be replicated in humans and hope to have results in about six months, Stockinger adds. 

The Francis Crick Institute researchers also plan to study the effects of a wider range of fruit and vegetables in their future studies to see if the results are mimicked: “Our study is linked with broccoli but, in the future, we predict a lot of phytochemicals will have this activity. And now that we know the molecular mechanisms of what is altered, it provides us with a good tool to test all types of phytochemicals for AhR activity.”

Research investigating the connections between fruit and vegetables and colon inflammation has been gaining ground. A recent study discovered how a cupful of strawberries a day could mitigate colonic inflammation and improve gut health, which is of particular significance to those suffering from Inflammatory Bowel Disease (IBD). The study, led by Hang Xiao, Ph.D., of UMass Amherst's Department of Food Science, also identifies how sedentary lifestyles and poor dietary patterns such as high-sugar, high-fat, high animal fat but lower fiber, can promote colonic inflammation.

By Laxmi Haigh