August 25, 2020
And, as we’re discovering through our own research studies, they play a vital role in determining your unique personal responses to food.
There has been an explosion in research into the community of microbes that live in our gut, known as the gut microbiome, in recent years. Research has linked our gut bacteria to how efficiently our body breaks down food, the health of our immune system, and even our brain function.
Microbes begin to populate our gut on the day we are born (and possibly even before). But the microbes that live in our gut are not permanent residents. Like a thriving city, the inhabitants of our microbial habitat come and go over time.
But exactly which microbes live in our gut depends on many factors. Diet is an obvious example, and people who eat a wide variety of plant-based foods usually have a more diverse gut microbiome.
Intriguingly, genetics seems to play only a minor role – we’ve found that identical twins only share a third of their gut bacteria (only slightly more than two unrelated people) and that on a strain level our gut microbiome’s are virtually unique!
We’ve all been told that our genes make us who we are, but it turns out that our gut bacteria also have a powerful influence on our health.
Scientists sometimes refer to the microbiome as the ‘second genome’ because the inhabitants of our gut supply thousands of genes, enzymes, and biochemical pathways that we can’t provide for ourselves.
The functions provided by our gut bacteria are extensive, from digesting fiber or producing essential vitamins and messenger molecules to fighting off disease and maybe even manipulating our moods.
Substances produced by our gut bacteria are absorbed into our blood via our intestinal cells and perform functions in our organs, immune system, and nervous system. For example, propionate, a molecule produced by our gut bacteria when they digest fiber, sets off a chain of events in the body leading to improved blood sugar control.
A healthy gut full of microbes also doesn’t leave much space or resources for pathogens, and our microbiome helps to defend against harmful pathogens by occupying the available space and living on all the food that’s in there. The ‘friendly’ bacteria in our gut even produce substances that kill or inhibit unwelcome visitors.
The bacteria that live in our gut may explain why even identical twins with the same genes respond to the same foods differently. Scientists can accurately predict how our blood sugar changes after food using data about our gut bacteria. In contrast, our genetic data do not accurately predict our responses to food.
Researchers have found that the identity of the microbes living in our gut can also impact the effectiveness of changes to how we eat. A 2015 study from the University of Gothenburg showed that people with high levels of a particular type of bacteria in their gut called Prevotella responded better to dietary changes intended to improve blood sugar control.
Like any ecosystem, the community of microbes in our gut is a delicate balance. When the microbes in our gut are out of balance (known as dysbiosis), we can often run into problems. This imbalance has been associated with a range of conditions, including inflammatory bowel disease, chronic fatigue syndrome, and even cancer. We don’t entirely understand it yet, but stress, illness, being overweight, overuse of antibiotics, and eating poor quality food are all thought to be contributing factors.
It is hard to say precisely what constitutes a healthy gut, but one thing researchers do agree on is that a more diverse microbiome is generally a healthier microbiome.
Research suggests that having a wide array of microbes in our gut makes our microbiome more capable and resilient. A diverse microbiome can function better than a microbiome with only a few kinds of bacteria because if one microbe is unable to fulfil its function, another is available to step in.
Unlike our genetics, we can influence which bacteria live in our gut. While some of the factors that affect the bacteria that live in our gut are difficult to change - like genetics, stressful events, or illness - we can modify and control our lifestyle behaviors.
The food we eat is one of the most important factors influencing the bacteria that live in our gut. Partially digested food, drugs, supplements and anything else we consume reach our gut and feed the bacteria living in there. The best diet for gut bacteria is thus a diverse one that includes a range of different foods.
Some species of bacteria prefer certain foods over others, so we can influence the bacteria that live in our gut with the food we eat. As an example, if you only ate bananas all day, every day, you’d end up with a gut full of banana-loving bacteria.
Unfortunately, industrial farming practices and processed foods have reduced the diversity of the food available to us. Today, 75% of the world’s food originates from only twelve plants and five animals. Antibiotics which are widely used in meat and some fish production, further reduce the diversity of the bacteria living in our gut.
What’s more, fad diets that restrict certain food groups can accidentally end up eliminating important populations of gut microbes by removing their favorite foods.
Here at ZOE, we believe that improving your gut health and avoiding dietary inflammation by eating the right foods for your biology is key to achieving a healthy weight and long-term health.