Cultural knowledge, having withstood the test of time, has proven itself right again. The saying, “you are what you eat” has never become truer than today as the scientific community is learning more and more about the microbes in our gut. What we eat influences the population of beneficial bacteria residing in our stomach and could potentially impact overall health and wellbeing.
Humans have ten times more microbial cells than human cells, and the collection of these microbes in our bodies is called the microbiota. These microbes are linked to important functions of our body, from training our immune system to identify harmful and beneficial microorganisms to sending neurochemicals up to the brain to affect brain development and activity [, ]. While most studies have yet to establish causation, there has been a steady positive correlation between a diverse microbial population and health.
A depiction of microbiota. Photo: Katie Scott
Researchers noticed that as societies mature to resemble developed nations, many key species of microbes disappear and higher incidents of chronic diseases are observed []. To understand this trend, researchers have been looking into the so-called “Western diet”, which is rich in animal meat and low in fiber. More and more studies are showing that the features of a meat-intensive diet may not be compatible with the microbes in our body and may even alter the microbiota in ways that are harmful to us.
Industrialized nations tend to eat high portions of meat, which contains a compound called carnitine (with red meat especially having high levels of carnitine). Through the activity of our gut microbiota, a chemical compound called TMAO is produced from carnitine. TMAO is associated with plaque buildup in artery walls and is considered a marker for cardiovascular disease. One major factor associated with TMAO production is previous dietary habits. In one study, long-term vegans and vegetarians (after consenting to eating red meat) showed significantly less TMAO formation compared to omnivores. More importantly, vegans and vegetarians have a different microbiota composition than meat eaters, leading to the hypothesis that increased levels of carnitine from consuming red meat alters the gut microbiota so that species involved in TMAO production dominate [].
By eating a diet heavy on animal products, we are only allowing a small group of microbes to thrive in our digestive system. It is recommended that humans should have a diverse microbiota but the trend leans towards the disappearance of more and more key species from the human gut. When we are eating, we are not only feeding ourselves but also the trillions of microbes within us. What would a diet that keeps our gut microbes happy, healthy and diverse look like? The answer seems to be in increased fiber consumption.
Dietary fibers are long chains of sugar molecules that are hard to break down. Fiber-fermenting microbes in our gut are capable of breaking it down to short-chain fatty acids that maintain the lining of our digestive system. When we don’t feed our fiber-loving microbes and they starve off and disappear (such as in the case of replacing microbes that break down fibers with microbes that break down carnitine in meat-heavy diets), the lining breaks down due to the lack of short-chain fatty acids and harmful microbial substances called endotoxins leak into the bloodstream. This initiates chronic inflammation that is associated with many diseases []. While many processed foods claim to be infused with fiber, they only contain a single kind of fiber. However, different microbes have different fiber preferences []. To address this issue, we have to move towards a fiber-rich and plant-based diet. Not only will this help bring back some of the fiber-fermenting microbes that promote good health, but eating lots of grains, vegetables and fruits also supplies a wide variety of fiber that can nourish a diverse set of microbes.
Keeping our microbes happy is just one of the many benefits of adopting a plant-based diet. Shifting to a diet rich in plant material is also advantageous to the planet! According to Drawdown, a program that ranks climate solutions based on effectiveness, changing to a plant-based diet is one of the most impactful ways a person can combat climate change. The livestock industry ranks high in terms of emissions, and this is fueled largely by the demand for meat products as the Western diet gains in popularity in other nations. Drawdown defines a plant-rich diet as one that involves a) restricting to 2500 kilocalories per day, b) reducing consumption of red meat and other meat-based proteins, and c) purchasing local products when possible. It was estimated that a total of 66 gigatons of CO2 emissions will be reduced by 2050 even if only half of the global population shifts to this kind of diet []. Most of the emissions being reduced come from decreased deforestation. Cattle is the most resource-intensive livestock, demanding large amounts of feed and pasture land. As a result, forests are being cleared at an alarming rate so that more land is available for these livestock [].
Eating right is one of the simplest yet most powerful ways to care for ourselves and the planet. There are many reasons why we should seriously start considering a plant-based diet. There is a large amount of data out there that asserts that a plant-based diet is one of the top ways that we can reduce our carbon footprint. To get even more personal, making conscious food choices will nourish the population of microbes that thrive in us and help us. Our gut microbiota will thank us generously when we feed them their favorite foods!