The world of Tzu Chi June 2021 (Vol.135)

TZU CHI 135 59 Ng Hui Ling A nutritionist with a Bachelor’s degree in Nutrition and a Master’s degree in Sports Science. She had served with the Singapore Heart Foundation before becoming a self-employed dietary consultant to vegetarians and a contributor for a health magazine. gut microbes need? The human digestive system does not have enzymes that can break down dietary fibre in plant-based food, such as fruits, vegetables and whole grains. When the dietary fibre that is indigestible by the human body arrives at the large intestine ready to be excreted, gut microbes will welcome them—their long- awaited food—with open arms, and break them down into short-chain fatty acids with smaller molecules. I believe readers have heard the term “prebiotics”, which refer to these dietary fibres. Interestingly, different microbes will take different prebiotics as their food, just like us humans, taking different staple foods based on different regions and cultures. When Rui Jia heard this, she asked me a very interesting question, “If we do not eat fruits and vegetables, what would these gut bacteria eat then?” I squinted, smiled, and gave her a reply that creeped her, “The answer is simple, isn’t it? They would just ‘eat’ you up!” I took out a pen and paper, drew the human intestines and explained to her. The outermost layer of our large intestine is the mucus layer. Mucus is secreted by the intestinal epithelial cells, and has a protective effect against pathogens. When a person’s diet contains too little dietary fibre and the gut microbes do not get enough food, some of them will then turn to the mucus layer and consume the mucus. If the speed of mucus production is not as fast as it is being consumed, obviously, the mucus layer will become thinner. And if this mucus layer, which is the first line of defence of the intestinal wall, is not strong enough, bacteria will invade the intestinal epithelial cells and trigger the immune system, which, in turn, will cause an inflammatory response. “You have to eat a variety of different plant-based foods!” I reminded Rui Jia. There are many types of dietary fibre, and I believe inulin and fructooligosaccharides (FOS) are the ones that are more familiar to everyone. Fibre is not only beneficial to the human body, but prebiotics, such as FOS and inulin also nourish different microbes in the gut. Therefore, eating too much of a certain fibre will reduce the diversity of gut microbes. This serves as another reminder of the importance of dietary diversity. Like many people, Rui Jia thought that we can ensure a healthy gut as long as we eat “good bacteria”. I did not mean to crush Rui Jia’s fantasy bubbles about the cultured milk that she loves to drink. I only shared with her, as the opportunity came, about how to eat properly and how we can coexist peacefully with the gut microbes. For example, eat more vegetables so that we can have a balanced and species-rich gut ecosystem. I also hope that when readers think about maintaining good health, they will level up: by not simply following the trends of consuming various probiotics and neglecting the importance of cultivating their own microbes.