Written by: Ms. Kristy Dockstader and Mr. Maunish Barvalia
The digestive tract is an important system that allows living things to absorb nutrients and excrete waste. The foods that you ingest are broken down in multiple ways as they travel through the digestive tract. Eventually microscopic pieces of food make their way to the small and large intestine. In the intestines, the nutrients are extracted and absorbed by the human body and by the trillions of gut bacteria that also live there. These bacteria play a crucial role in the holistic health of the body and are extremely sensitive to changes in the human diet.
In recent years, scientists and health professionals have taken a much closer look at how gut bacteria, also known as the gut microbiota, plays a role in various aspects of human health. The gut microbiota has been shown to have a role in the development of allergies, gastro intestinal ailments and even aspects of brain function and moods. The human digestive tract is home to around hundred trillion bacteria and each person has their own unique microbiota.
The bacteria living within humans first colonize the body at birth as the baby is leaving its mothers birth canal and continues to flourish as the baby grows and develops. The types of bacteria in your digestive tract change and develop based on the food you eat, the water you drink and the antibiotics you are exposed to, along with many other everyday factors in your life. In a recent article published in the esteemed journal of Nature Microbiology, scientists from Duke University looked at the importance of protein in the diet by examined how lack of nitrogen affects gut bacteria in mammals1.
Nitrogen is an essential element for all living things, as it is required to form some of the building blocks of life. Nitrogen is easily consumed in the diet in the form of protein. A few high protein foods include eggs, fish, meats, soy, beans, nuts and lentils. Many more examples of foods that are great in protein can be found here.
Within this study, scientists looked at how nitrogen limitations (low protein diet) affect the gut bacteria of 30 mammalian species, including humans. Their research suggests that low levels of nitrogen in the gut leads to reduced numbers of good bacteria types that are important for the digestion of some sugar, and that help provide nutrients for many other important types of bacteria in the gut.
Limitations of nitrogen for gut bacteria not only reduce the number of good bacteria but also affect carbon levels in the digestive tract. Carbon is another essential element and is usually absorbed in the form of carbohydrate, or sugars, that can be further broken down by the body for energy. The study found that more carbon was excreted in the feces when mice were given a low protein (low nitrogen) diet compared to average or high protein diets. This is thought to be the bodies way of maintaining a good nutrient ratio in the gut. Having too much carbohydrates without enough nitrogen in the diet causes good bacteria to work less efficiently. When the good bacteria are working less efficiently, not all of the nutrients you are eating will actually be able to be used or broken down and instead, end up being excreted as waste. This suggests that by not consuming adequate levels of protein in the diet, it can also cause the body to have difficulty absorbing other important nutrients as well.
Mammals and bacteria have co-evolved together over millions of years. In that time, many bacteria have developed a relationship that is not only beneficial for themselves but are also very beneficial for the hosts they inhabit. The amount of protein needed by an individual can vary greatly depending on age, weight and activity level. On average, a healthy, fit women over the age of 19 should consume 46g of protein per day and 56g for the male counterpart. If you are a very active individual, you may require even higher levels of protein for optimal body health. This website can give you a visual idea of what 25g of protein looks like. If you are a vegetarian, 17 best protein sources can be found here. By providing our good bacteria with the nutrients that allow them to grow and flourish, they also help make our bodies healthier and stronger on a holistic level.
Paper of interest:
1 Reese, A. T. et al. Microbial nitrogen limitation in the mammalian large intestine. Nat Microbiol, doi:10.1038/s41564-018-0267-7 (2018).