When you eat, you never eat alone. The bacteria in your gut feed along with you and they have a bigger role to play in your health than you think.
Your gut is filled with trillions of good and bad bacteria. When you eat, these bacteria eat along with you. You may be surprised to find that a wide diversity of bacteria is needed to maintain not only your health, but also your weight. According to European research, gut bacteria in a quarter of the population is too low. In particular, obese people have 40 per cent less intestinal bacteria than what is needed to maintain optimal health. These obese people also have reduced bacterial diversity and harbour more obesity-promoting bacteria known as Firmicutes, which cause low-grade inflammation in the body. Mild inflammation in the digestive tract is reflected in blood samples and reveals a state of chronic inflammation, which affects metabolism and increases the risk of diseases such as type 2 diabetes and heart disease. Therefore, your food choices not only feed you, they also feed the bacteria that reside in your gut.
The Gut at a Glance
Everything you eat and drink passes along your gastrointestinal tract (GIT). This tube-like structure is lined with a thin, sticky mucous that is embedded with millions of bacteria that live, grow, digest and absorb the substances present in your GIT. These bacteria (known as the intestinal microbiota or gut flora) are a combination of both beneficial and harmful bacteria, and they promote normal functioning of the gut, protect the body from infection, extract nutrients and energy from your diets, regulate the mucosal immune system, and maintain and protect the gut barrier. Disruptions to the normal balance between the gut microbiota and the host (you) has been associated with obesity, inflammatory bowel disease, malnutrition and cancer. What constituents a “normal” gut microbiota is hard to determine however, as there is a large variation in microbiota diversity among individuals and populations.
What is known however, is having higher levels of good bacteria helps to maintain an intact gut barrier, which prevents the potential invasion of the intestinal mucosa by incoming harmful foreign substances. The good bacteria fights against these harmful substances by detoxifying them and easing their elimination. The good bacteria produce an acidic environment that prevents their growth. Carbohydrates that escape digestion and absorption in the small intestine undergo fermentation in the colon and produce short-chain fatty acids (SCFAs), mainly acetate, propionate, and butyrate. These SCFAs have a profound affect on gut health as they work as an energy source, an inflammatory modulator, a vasodilator and play a part in gut motility and wound healing. In addition, SCFAs are absorbed by the colon, where butyrate provides energy for colon cells, and acetate and propionate reach the liver and peripheral organs, where they are used in lipogenesis (conversion of sugars to fatty acids) and gluconeogenesis (generation of glucose from non-carbohydrate substrates). As well as being an important energy source, SCFA also play a role in two G-protein receptors that stimulate the secretion of the hormone PYY, which inhibits gut motility, slowing how quickly food is transported through the gut, thereby enhancing nutrient absorption and increasing satiety. With more research, the roles of gut microbiota in our health and weight may continue to grow.
How Food Alters Your Gut Microbiota
While food isn’t the only thing that alters the gut microbiota, it’s an essential factor that cannot be overlooked. Certain bacteria in the gut influence how much energy is extracted from food and stored as fat. According to research, 90 per cent of the bacteria in the human gut microbiota belongs to Firmicutes and Bacteroidetes. Compared to Firmicutes, Bacteroidetes are less efficient at harvesting kilojoules and nutrients from food. We know that obese people have higher levels of Firmicutes and lower levels of Bacteroidetes, and that the number of these bacteria in the gut can respond to changes in body weight. High kilojoule diets have been found to increase the growth of the Firmicutes in the gut of people and mice. The more kilojoules consumed, the more Firmicutes in the gut and the more efficiently intestinal cells absorb fat. However, when obese people (as well as mice) are placed on either a low-fat or low-carb diet, the number of Firmicutes decreases and the Bacteroidetes proliferate, promoting leanness.
Simply changing from a westernised diet that high in fat and sugar to a low-fat, plant-based diet can improve the gut microbiota in obese people. In fact, in 2009 a study in germ-free mice with transplanted human gut microbes who were switched from a low-fat plant-based one to a more westernised diet high in fat and sugars, obesity-associated microbes were thriving in the animal’s guts within one day. Not only did the westernised diet seem to encourage gut colonisation by more obesity-related microbes, but it also appeared to discourage colonisation of microbes associated with leanness, leading to weight gain and the development of metabolic problems. So, to improve the health of your gut include more plant-based foods that are rich in fibre and prebiotics, as well as including a probiotic, limiting or avoiding toxins in food and managing your stress levels.
How do you look after your gut health?