The environmental benefits of eating less animal-sourced foods have been touted so frequently that this advice is “old news”. Suggesting that choosing plant-based diets could Save The World generates little excitement, despite attractive benefits that include less agricultural land use, reduced greenhouse gas emissions, and improved health. However, recent research suggests that the effects of climate change make the advice more important than ever before. Beyond being good for the planet, we now have new reasons for why plant-based diets are important for our health. Human gut microbiota cooperate to transform animal-sourced foods into cancer-promoting toxins, while byproducts of plant foods energize and sooth our digestive tract.
Our digestive tract is populated by trillions of nearly invisible microorganisms, which help us digest food, obtain nutrients, and maintain immunity. These microbes primarily function by fermenting foods we eat to generate energy, creating byproducts that can either promote or detract from intestinal health in the process. A healthy gut community is well balanced in type and number of species, and generates byproducts that energize human colon cells and prevent disease-causing pathogens from entering the system.
Perhaps the most important trait of a healthy gut is an intact protective lining, made up of slimy mucins separating the intestinal cells from harmful organisms or toxins travelling through the digestive tract. Microbial grazing, or selective feeding by microbes on gut surface mucins, can damage underlying cells and degrade this protective lining. Exposed intestinal cells then initiate an inflammatory immune response that can contribute to the development and progression of chronic diseases including obesity, cardiovascular disease, cancer, and diabetes.
The processes by which gut microbial activities affect gut health is being investigated in the Weir Lab at Colorado State University, where I am currently a PhD candidate. Recently, we examined data from a dietary intervention in colorectal cancer survivors, which supplemented one of two high-fiber plant foods, rice bran or navy beans. We wanted to see if these foods have the potential to alter gut microbes and their metabolites and reduce intestinal diseases. The data showed that rice bran consumption might indeed do just that.
Study participants who consumed rice bran had higher populations of the friendly gut microbe Bacteroides ovatus, an organism that competes with and excludes other harmful microbes that target gut mucins as a “favorite food”. B. ovatus prefers fiber components found in rice bran called xylans, which it transforms into beneficial byproducts that control appetite, reduce inflammation, and prevent cancerous tumors. Xylans structurally resemble gut mucins and are only found in plant-based foods. Research by other teams suggests that a diet devoid of xylans and other fiber starves gut microbes, forcing them to resort to feeding on the intestinal lining. Preventing breakdown of intestinal lining and resulting inflammation and immune activity could explain the importance of plant-based foods in human health, but gut microbes don’t transform all foods into beneficial byproducts. In fact, red meat and high fat diets become a source of cancer-causing toxins during microbial digestion.
Research from Oxford University by the Scarborough lab suggests that the benefits of plant-based diets extend far beyond intestinal health. Greenhouse gas emissions are reduced by 29-70% (depending on whether food processing is included) and water usage is also minimized. Given that 70% of water is used for food production and that producing plant foods uses less water, choosing plant-based over animal-based products can become an important part of water conservation. Money can also be saved. The Scarborough team estimates that a global dietary shift toward a plant-based diet could save $1 trillion in health care costs and $30 trillion in lost productivity. They also suggest that climate change will decrease both the global food supply and dietary quality enough to directly cause 500,000 deaths by 2050. As crop yields dwindle due to climate change, the ability of plant foods to maximize production while using less energy will provide a valuable strategy for providing the world with enough food.
In considering an individual’s contribution to global sustainability, few decisions make as much impact as the one we make several times a day when we decide what to eat. Some suggest that in the coming decades up to 740 million lives, or 10% of the world population, could be spared from death due to under-nutrition by reducing or eliminating human consumption of animal-sourced foods. The potential benefits are so profound and widespread that TIME magazine recently published an article titled ‘How a Vegetarian Diet Could Help Save the Planet’. Of course, these benefits aren’t limited to strict vegetarianism; replacing some or most animal foods with plant foods also improves sustainability. Emphasizing plant foods in your diet is a simple yet powerful way to promote personal health, reduce carbon footprints, save water, and feed a growing population in an era of climate change.