Your body is full of trillions of bacteria, viruses and fungi. They are collectively known as the microbiome.
While some bacteria are associated with disease, others are actually extremely important for your immune system, heart, weight and many other aspects of health.
This article serves as a guide to the gut microbiome and explains why it’s so important for your health.
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What Is the Gut Microbiome?
Bacteria, viruses, fungi and other microscopic living things are referred to as microorganisms, or microbes, for short.
Trillions of these microbes exist mainly inside your intestines and on your skin.
Most of the microbes in your intestines are found in a “pocket” of your large intestine called the cecum, and they are referred to as the gut microbiome.
Although many different types of microbes live inside you, bacteria are the most studied.
In fact, there are more bacterial cells in your body than human cells. There are roughly 40 trillion bacterial cells in your body and only 30 trillion human cells. That means you are more bacteria than human (1Trusted Source, 2Trusted Source).
What’s more, there are up to 1,000 species of bacteria in the human gut microbiome, and each of them plays a different role in your body. Most of them are extremely important for your health, while others may cause disease (3Trusted Source).
Altogether, these microbes may weigh as much as 2–5 pounds (1–2 kg), which is roughly the weight of your brain. Together, they function as an extra organ in your body and play a huge role in your health.
The gut microbiome refers to all of the microbes in your intestines, which act as another organ that’s crucial for your health.
How Does It Affect Your Body?
Humans have evolved to live with microbes for millions of years.
During this time, microbes have learned to play very important roles in the human body. In fact, without the gut microbiome, it would be very difficult to survive.
The gut microbiome begins to affect your body the moment you are born.
You are first exposed to microbes when you pass through your mother’s birth canal. However, new evidence suggests that babies may come in contact with some microbes while inside the womb (4Trusted Source, 5Trusted Source, 6Trusted Source).
As you grow, your gut microbiome begins to diversify, meaning it starts to contain many different types of microbial species. Higher microbiome diversity is considered good for your health (7Trusted Source).
Interestingly, the food you eat affects the diversity of your gut bacteria.
As your microbiome grows, it affects your body in a number of ways, including:
Therefore, there are a number of different ways in which the gut microbiome can affect key bodily functions and influence your health.
The gut microbiome affects the body from birth and throughout life by controlling the digestion of food, immune system, central nervous system and other bodily processes.
The Gut Microbiome May Affect Your Weight
There are thousands of different types of bacteria in your intestines, most of which benefit your health.
However, having too many unhealthy microbes can lead to disease.
An imbalance of healthy and unhealthy microbes is sometimes called gut dysbiosis, and it may contribute to weight gain (21Trusted Source).
Several well-known studies have shown that the gut microbiome differed completely between identical twins, one of whom was obese and one of whom was healthy. This demonstrated that differences in the microbiome were not genetic (22Trusted Source, 23Trusted Source).
Interestingly, in one study, when the microbiome from the obese twin was transferred to mice, they gained more weight those that had received the microbiome of the lean twin, despite both groups eating the same diet (22Trusted Source).
These studies show that microbiome dysbiosis may play a role in weight gain.
Fortunately, probiotics are good for a healthy microbiome and can help with weight loss. Nevertheless, studies suggest that the effects of probiotics on weight loss are probably quite small, with people losing less than 2.2 pounds (1 kg) (24Trusted Source).
It Affects Gut Health
The microbiome can also affect gut health and may play a role in intestinal diseases like irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) (25Trusted Source, 26Trusted Source, 27Trusted Source).
The bloating, cramps and abdominal pain that people with IBS experience may be due to gut dysbiosis. This is because the microbes produce a lot of gas and other chemicals, which contribute to the symptoms of intestinal discomfort (28Trusted Source).
However, certain healthy bacteria in the microbiome can also improve gut health.
Certain Bifidobacteria and Lactobacilli, which are found in probiotics and yogurt, can help seal gaps between intestinal cells and prevent leaky gut syndrome.
These species can also prevent disease-causing bacteria from sticking to the intestinal wall (29Trusted Source, 30Trusted Source).
In fact, taking certain probiotics that contain Bifidobacteria and Lactobacilli can reduce symptoms of IBS (31Trusted Source).
How Can You Improve Your Gut Microbiome?
There are many ways to improve your gut microbiome, including:
Eating a wide variety of high-fiber and fermented foods supports a healthy microbiome. Taking probiotics and limiting antibiotics can also be beneficial.
The Bottom Line
Your gut microbiome is made up of trillions of bacteria, fungi and other microbes.
The gut microbiome plays a very important role in your health by helping control digestion and benefiting your immune system and many other aspects of health.
An imbalance of unhealthy and healthy microbes in the intestines may contribute to weight gain, high blood sugar, high cholesterol and other disorders.
To help support the growth of healthy microbes in your gut, eat a wide variety of fruits, vegetables, whole grains and fermented foods.