There are around 40 trillion bacteria in your body, most of which are found in your gut.
Collectively, they are known as your gut microbiome, and they’re incredibly important for overall health. However, certain types of bacteria in your intestines can also contribute to many diseases.
Many factors, including the foods you eat, can impact the type of bacteria found in your digestive tract.
Here are 9 science-based ways to improve your gut bacteria.
1. Eat a diverse range of foods
There are hundreds of species of bacteria in your intestines, each of which plays a specific role in health and requires different nutrients for growth.
Generally speaking, a diverse microbiome is considered a healthy one. This is because the more species of bacteria you have, the more health benefits they may be able to contribute to.
A diet consisting of different food types can lead to a more diverse microbiome.
Unfortunately, the traditional Western diet is not very diverse and is rich in fat and sugar. In fact, an estimated 75% of the world’s food is produced from only 12 plant and 5 animal species.
However, diets in certain rural regions are often more diverse and richer in different plant sources.
For this reason, a few studies have shown that gut microbiome diversity is much greater in people from rural regions of Africa and South America than in people from urban areas in Europe or the United States.
Summary: Eating a diverse diet rich in whole foods can lead to a diverse microbiome, which is beneficial for your health.
2. Eat lots of vegetables, legumes, beans, and fruit
Fruits and vegetables are the best sources of nutrients for a healthy microbiome.
They are high in fiber, which your body can’t digest. However, certain bacteria in your gut can digest fiber, which stimulates their growth.
Beans and legumes also contain very high amounts of fiber.
Some high fiber foods that are good for your gut bacteria include:
- Green peas
- Whole grains
One study found that following a diet rich in fruits and vegetables prevented the growth of some disease-causing bacteria.
Apples, artichokes, blueberries, almonds, and pistachios have also all been shown to increase Bifidobacteria in humans.
Bifidobacteria are considered beneficial bacteria, as they can help prevent intestinal inflammation and enhance gut health.
Summary: Many fruits and vegetables are high in fiber. Fiber promotes the growth of beneficial gut bacteria, including specific types such as Bifidobacteria.
3. Eat fermented foods
Fermented foods have undergone fermentation, a process in which the sugars they contain are broken down by yeast or bacteria.
Some examples of fermented foods are:
Many of these foods are rich in lactobacilli, a type of bacteria that can benefit your health.
Research shows that people who eat a lot of yogurt appear to have more lactobacilli in their intestines. These people also have less Enterobacteriaceae, which is a type of bacteria associated with inflammation and a number of chronic conditions.
Similarly, a number of studies have shown that yogurt consumption can improve intestinal bacteria and decrease symptoms of lactose intolerance.
What’s more, yogurt may also enhance the function and composition of the microbiome.
However, many yogurts, especially flavored yogurts, contain high amounts of sugar. Therefore, it’s best to opt for plain, unsweetened yogurt or a flavored yogurt with minimal added sugar that is made only of milk and bacteria mixtures, also sometimes called “starter cultures.”
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Additionally, to reap the gut health benefits, make sure the label reads “contains live active cultures.”
Furthermore, fermented soybean milk may promote the growth of beneficial bacteria, such as Bifidobacteria and lactobacilli, while decreasing quantities of some other harmful strains of bacteria. Kimchi may also benefit the gut flora.
Summary: Fermented foods like plain yogurt can benefit the microbiome by enhancing its function and reducing the abundance of disease-causing bacteria in the intestines.
4. Eat prebiotic foods
Prebiotics are foods that promote the growth of beneficial bacteria in the gut.
They are mainly fiber or complex carbs that human cells cannot digest. Instead, certain species of bacteria in the gut break them down and use them for fuel.
Many fruits, vegetables, and whole grains contain prebiotics, but they can also be found on their own.
Resistant starch can also be a prebiotic. This type of starch is not absorbed in the small intestine and passes into the large intestine, where the microbiota break it down.
Many studies have shown that prebiotics can promote the growth of several types of beneficial bacteria, including Bifidobacteria.
Certain prebiotics have also been shown to reduce insulin, triglyceride, and cholesterol levels in people with obesity, which could be beneficial for the prevention of conditions like heart disease and type 2 diabetes.
Summary: Prebiotics promote the growth of several types of beneficial bacteria, including Bifidobacteria. Some studies suggest that prebiotics could also reduce risk factors for certain health conditions by decreasing levels of insulin, triglycerides, and cholesterol.
5. If you can, breastfeed for at least 6 months
A baby’s microbiome begins to properly develop at birth. However, studies suggest that babies may be exposed to some bacteria even before birth.
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During the first 2 years of life, an infant’s microbiome is continuously developing and is rich in beneficial Bifidobacteria, which can digest the sugars found in breast milk.
Many studies have shown that infants who are fed formula have an altered microbiome with fewer Bifidobacteria than infants who are breastfed.
What’s more, breastfeeding is also associated with lower rates of allergies, obesity, and other health conditions that may be due to differences in the gut microbiota.
Summary: Breastfeeding helps an infant develop a healthy microbiome, which may help protect against certain health conditions later in life.
6. Eat whole grains
Whole grains contain lots of fiber and nondigestible carbs, such as beta-glucan. These carbs are not absorbed in the small intestine and instead make their way to the large intestine to promote the growth of beneficial bacteria in the gut.
Research suggests that whole grains can promote the growth of Bifidobacteria, lactobacilli, and Bacteroidetes in humans.
In these studies, whole grains also increased feelings of fullness and reduced inflammation and certain risk factors for heart disease.
However, keep in mind that some research shows that gluten-containing grains — such as wheat, barley, and rye — may actually negatively impact gut health by increasing intestinal permeability and inflammation in some people.
While this mostly applies to those with celiac disease or a sensitivity to gluten, more research is needed to determine whether eating grains that contain gluten may also alter the gut microbiome in healthy adults without these conditions.
Summary: Whole grains contain nondigestible carbs that can promote the growth of beneficial bacteria within the gut microbiome. These changes to the gut flora may improve certain aspects of metabolic health.
7. Eat a plant-based diet
Diets containing animal-based foods promote the growth of different types of intestinal bacteria than plant-based diets do.
A number of studies have shown that vegetarian diets may benefit the gut microbiome, which may be due to their high fiber content.
For example, one small 2013 study found that a vegetarian diet led to reduced levels of disease-causing bacteria in people with obesity, as well as reductions in body weight, inflammation, and cholesterol levels.
A 2019 review noted that plant foods are rich in specific nutrients that can increase levels of beneficial bacteria and decrease harmful strains of bacteria to support gut health.
However, it is unclear if the benefits of a vegetarian diet on the gut microbiome are due to a lack of meat intake or if other factors may also play a role.
Summary: Vegetarian and vegan diets may improve the microbiome. However, it is unclear if the positive effects associated with these diets can be attributed to a lack of meat intake or if other factors may be involved.
8. Eat foods rich in polyphenols
Polyphenols are plant compounds that have many health benefits, including reductions in blood pressure, inflammation, cholesterol levels, and oxidative stress.
Human cells can’t always digest polyphenols. Because they aren’t absorbed efficiently, most polyphenols make their way to the colon, where they are digested by gut bacteria.
Some examples of foods rich in polyphenols are:
- Cocoa and dark chocolate
- Red wine
- Grape skins
- Green tea
Polyphenols from cocoa can increase the amount of Bifidobacteria and lactobacilli in humans and reduce the quantity of Clostridia.
Furthermore, these changes in the microbiome are associated with lower levels of triglycerides and C-reactive protein, which is a marker of inflammation.
The polyphenols in red wine have similar effects and have even been shown to increase levels of beneficial bacteria in people with metabolic syndrome.
Summary: Polyphenols can’t be digested efficiently by human cells, but they are efficiently broken down by the gut microbiota. They may improve several health outcomes related to heart disease and inflammation.
9. Increase your intake of probiotics
Probiotics are live microorganisms, usually bacteria, that provide a specific health benefit when consumed.
Probiotics don’t permanently colonize the intestines in most cases. However, they may benefit your health by changing the overall composition of the microbiome and supporting your metabolism.
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A review of seven studies found that probiotics have little effect on the gut microbiome composition of healthy people. However, there is some evidence that probiotics may improve the gut microbiome in those with certain diseases.
One review of 63 studies found mixed evidence of the effectiveness of probiotics in altering the microbiome. But the researchers noted that the probiotics’ strongest effects seemed to be in restoring the microbiome to a healthy state after it had been compromised.
Nevertheless, some studies have shown that probiotics can improve the functioning of certain gut bacteria, as well as the specific types of chemicals they produce.
You can increase your intake of probiotics by consuming more probiotic-rich foods, including fermented foods like kimchi, kefir, sauerkraut, and yogurt.
Alternatively, you can consider using a probiotic supplement. However, be sure to talk with your doctor before starting supplementation, especially if you are taking other medications or have any underlying health conditions.
Summary: Probiotics do not significantly change the composition of the microbiome in healthy people. However, they may improve microbiome function and help restore the microbiome to good health in those with certain health conditions.
Your gut bacteria are extremely important for many aspects of health.
Many studies have now shown that a disrupted microbiome can lead to numerous chronic diseases.
The best way to maintain a healthy microbiome is to eat a range of fresh, whole foods, mainly from plant sources like fruits, veggies, legumes, beans, and whole grains.