Trillions of bacteria and other microbes live in your gut, collectively known as the microbiome and weighing up to 2kg in total. But they aren’t unwanted guests – they help to digest your food and make a vital contribution to health.
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 brain function.
Microbes begin to populate our gut on the day we are born. 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 37% of their gut bacteria,only slightly more than two unrelated people.
Your gut microbiome has important effects on health
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.
Your microbiome affects how you respond to food
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, while our own research shows that genes don’t 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, 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.
A healthy microbiome is a diverse microbiome
It is hard to say precisely what constitutes a healthy gut. 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 fulfill its function, another is available to step in.
Unlike our genetics, we can influence which types of bacteria live in our gut. While some of the factors that affect the microbiome are difficult to change – like genetics, stressful events or illness – we can modify and control our lifestyle and diet.
How can you improve your microbiome diversity?
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.
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 – such as low-carbohydrate, carnivore or plant-only diets – can accidentally end up eliminating important populations of gut microbes by removing their favorite foods.
Want to boost your microbiome? Take a tip from hunter-gatherers
Hunter-gatherers have much more diverse gut bacteria than people living in urban populations, but they also have much more diverse diets.
The Hadza – a community of hunter-gatherers in Tanzania – eat a fantastic variety of plants and animals, chowing down around 600 species in total, compared with fewer than 20 in Western diets. Unsurprisingly, their microbiomes are also twice as diverse as those of Europeans.
But we can take some tips from them to improve the diversity of our own microbiomes, wherever we live: our scientific founder Tim Spector recently spent three days living with the Hadza and increased his gut bacteria diversity by 20%.
Here at ZOE, we value the importance of building a healthy gut through nutrition. What’s more, we understand that your gut bacteria can significantly impact your response to food and your health.
That’s why we’re measuring personal nutritional responses in thousands of people – the largest study of its kind in the world. We are combining large-scale data (including microbiome data) and machine learning to predict personal nutritional responses to any meal so you can eat with confidence.
Sign up to our early access mailing list to be the first to know how you can find the foods your body loves.
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