Desai talked to Delano about what happens if we don’t provide our bodies with sufficient fruit and veggies during an interview on Friday 29 September.
Laurence Schaack: Dr Desai, could you please explain your research and methodology to a non-scientific audience?
Mahesh Desai: Already our grandparents told us “eat fruit and vegetables”. It isn’t a new story and some of the benefits are known. But on a molecular level, it was poorly understood what happens if you don’t eat enough vegetables and fruit. So, in our study, we showed that when you don’t eat enough fibre [a nutrient in fruits and vegetables which helps with digestion], then the bacteria in your intestine that normally helps you to digest fibre by taking up its molecules, change their behaviour and look for alternative food sources. One of these alternative food sources is the mucus layer that is secreted in the intestine and that mucus attracts bacteria. In short, they start eating you from the inside. That mucus layer then gets reduced to a point where some pathogenic or harmful bacteria can easily invade inside the mucus--and this can lead to diseases.
A intact mucus (green) layer, generated by the cells of a mouse’s colon wall is pictured. The mucus enacts as a barrier for the “goblet” cells (blue) that produce it. Image: Luxembourg Institute of Health
What kind of diseases can be caused by a reduced mucus layer?
We showed in the paper that a E. coli-like pathogen causes colitis, an inflammation of the intestine. And in the long run, if you do not eat fibre, this may contribute to diseases such as inflammatory bowel disease and even colon cancer. The balance between the production of mucus and its degradation by bacteria is very important; if this balance is disturbed and bacteria start to excessively eat the mucus, this becomes very dangerous for the host and it could in the long run lead to the diseases I mentioned.
You also showed in your study that prebiotic supplementation does not cease the erosion of the mucus layer. Does this mean that prebiotics have been used the wrong way?
We don’t intend to object the implacability of prebiotics. However, we want to show that perhaps the form of prebiotics might not be highly suitable to its use by bacteria. Maybe I could first tell you what prebiotics are. Prebiotics means like bacteria, if ingested, they can help us to boost our immune system. On the other hand, prebiotics are polysaccharides that, if eaten, help to produce metabolites that are good for our health. So, currently on the market there are “prebiotics” that are highly purified. But in our study, we found that they are not available to the microbiota, they get depleted already in the upper part of the gastro-intestinal tract. So maybe, what our study indicates, it is important to design more complex prebiotics that they can be easily delivered all the way to the distil part of the intestine where the bacteria can digest them and release beneficial metabolites.
A graphical illustration of the study, visualising the mucus layer of a fibre-rich diet in comparison to the eroded mucus layer of a fibre-free diet. Image: Cell
How does your study open the ground for further research?
In line with what I mentioned already, we are looking into understanding how such change of bacteria could lead to diseases such as inflammatory bowel disease and even colon cancer. And we are at the same time interested in designing complex-branched prebiotics that might prevent occurances of such diseases. In the second part, we are keen on understanding how diet driven changes in the gut bacteria can contribute to different types of allergies, not just in the digestive area but also in the air ways, so that means in the lungs.
How much fibre should people consume to have an intact mucus layer in their guts?
If you look at the recommendations given by standard health agencies, they say 25 to 35 grams of fibre a day. Of course, it also depends on the individual person. I think eating at least 35 grams should be a good start, and one can then increase slowly, which should lead to a really good mucus layer and a strong immune system.