The microorganisms that make up your gut microbiome may not be visible to the eye, but they contribute in big ways to your health. Find out whether taking probiotics can help.

You might have noticed that gut health is all the rage these days. And as it turns out, it is for a very good reason. Scientists are discovering more and more that the gut - specifically, the “gut microbiome” - might be one of the key elements that contribute to overall health.

As awareness of the gut microbiome grows, there is an increased interest in ways to support and maintain a healthy gut microbiome.

So, what exactly is the gut microbiome, how might it improve health, and can probiotics really help?

What is the gut microbiome?

Inside the human digestive tract lives a diverse community of microorganisms that include bacteria, viruses, fungi, and their genes - a collection that is referred to as the “microbiome.” These microorganisms are abundant - there are as many of them as there are cells in the body - and they do not only exist in the gut. The skin, nasal cavities, and mouth also house different communities of microbes. Within the gut, most of these microorganisms can be found in the colon and include 200 to more than 1,000 species of bacteria, some of which are beneficial and some potentially harmful to the body.

A gut microbiome can generally be characterized by its abundance of specific species, the diversity of the microorganisms, and the number of certain species relative to others.

A healthy gut microbiome is diverse and one in which the body, the microbiome, and the environment maintain a balance of both helpful and harmful microorganisms that peacefully coexist. When this balance is disrupted - a state called dysbiosis- the body becomes more susceptible to disease.

The gut microbiome’s link to health

In healthy people, a diverse gut microbiome fills several critical roles. It provides protection from disease-causing cells, helps with synthesizing amino acids and vitamins like B vitamins and vitamin K, regulates the metabolism of fat, and stimulates the immune system while helping to manage inflammation in the gut.

The microbiome also helps with digestion. Unlike the sugars that are broken down from food and are easily absorbed in the upper part of the small intestine, complex carbohydrates, including fibers, are not as rapidly digested. These “indigestible” nutrients travel further to the large intestine, where bacteria produce enzymes that break them down while generating short-chain fatty acids, a group of fatty acids that serve as a source of energy and regulate nutrient absorption while keeping the movement of food through the digestive system flowing.

Extensive research has been done to study the association between the composition of the gut microbiome and the development of disease. A disrupted gut microbiome impairs short-chain fatty acid production, leading to cellular dysfunction. It has been linked to autoimmune disorders like rheumatoid arthritis, type 1 diabetes, eczema, and asthma, as well as inflammatory gut disorders, including irritable bowel syndrome and inflammatory bowel disease. An imbalance in the microbiome is also thought to contribute to the development of cardiometabolic diseases like type 2 diabetes and non-alcoholic fatty liver disease.

What helps shape the gut microbiome?

The nature of your gut microbiome was actually determined when you were born. It is unique to you and was initially tailored by your DNA and by the microorganisms that were passed down from your mother. As you grew, your microbiome shifted over time as a response to environmental exposures, medication use, and diet.

In fact, diet is largely considered one the most significant factors in determining gut microbiome health, starting during the very early years of life when drinking breast milk. The microbiome is then continually shaped toward healthy and balanced or a state of dysbiosis as a result of being exposed to other foods.

For example, research suggests that people who consumed ultra-processed foods in childhood or adolescence may have a higher chance of developing colon cancer and inflammatory bowel disease due to unhealthy changes in the gut microbiome. Also, people who follow diets high in fiber-rich plant foods show greater microbial diversity than those who include meat in their diets, indicating that eating more plants contributes to a healthier microbiome. This makes sense - the fermentation of fiber is needed by the microbiome to produce the beneficial short-chain fatty acids. Saturated fat from animal foods, on the other hand, is linked with an increase in inflammation and harmful bacteria.

Taking antibiotics can also change the gut microbiome. Antibiotics are medications designed to kill or inhibit the growth of bacteria for the treatment of bacterial infections. Unfortunately, these medications kill not only harmful bacteria but beneficial ones as well. This can decrease the microbiome’s diversity and cause an imbalance.

What are probiotics?

Probiotics have gained popularity in recent years as people have become more aware of the importance of gut health and are interested in natural ways to improve their health. Probiotics are live microorganisms that are beneficial to the body and are often referred to as “friendly” bacteria. The most common types of bacteria found in probiotics are part of the Lactobacillus and Bifidobacterium groups. Probiotics can be found in certain foods and dietary supplements and are taken to improve gut health and immunity.

Research on probiotics reveals that their health-giving bacteria are so helpful for the body largely because they produce effector molecules These small molecules bind to proteins and regulate the proteins’ biological activity. They impact protein functions by increasing or decreasing gene expression and enzyme activity and can also influence cell signaling.

Specifically, scientists theorize that probiotics may help prevent disease and contribute to health in four key ways:

1. Improving gut microbiome composition. Beneficial bacteria in probiotics compete with harmful microorganisms for nutrients and placement in the gut, which can help reduce the colonization and growth of disease-causing bacteria.

2. Regulating immunity. Probiotics can also help prevent disease by influencing effector molecule activity. Effector molecules produced by probiotics increase and activate the body’s immune cells, including regulatory T cells which help maintain immune system balance and prevent excessive immune responses that can lead to autoimmune diseases.

3. Maintaining the gut barrier. The gut barrier is the lining of the digestive tract, which acts as a physical barrier between the gut and the rest of the body. The gut barrier is made up of a layer of cells that are tightly joined together to form a barrier that prevents harmful substances, such as bacteria, viruses, and toxins, from passing from the inside of the digestive tract into the bloodstream and other tissues. Also, nutrients from food are transported across the barrier into the bloodstream, where they can be used for energy. Probiotics secrete bacteriocins, antimicrobial peptides that prevent invading bacteria from crossing the gut barrier to other tissues during infection.

4. Stimulating the vagus nerve. The vagus nerve is the longest nerve in the body that originates in the brain and travels through the neck, chest, and abdomen, reaching a range of organs and tissues, including the heart, lungs, stomach, liver, and kidneys. It activates the parasympathetic nervous system which controls digestion, heart rate, and respiration. It also plays a role in managing mood and stress responses by promoting relaxation. Evidence shows that vagus nerve activities are affected by gut bacteria. Specifically, certain bacterial strains are shown to use the vagus nerve’s signaling network to communicate with the brain and influence behavior.

How to get probiotics

Probiotics can be found in many fermented foods. Fermented foods contain various live strains of probiotics that can colonize the gut and improve the balance and diversity of the microbiome. These foods include kefir, tempeh, sauerkraut, miso, kimchi, sourdough bread, kombucha, and yogurt.

Probiotics can also be taken in the form of supplements, which contain freeze-dried live cells of probiotic strains and are available in capsules, tablets, powders, and liquids. Because they are marketed as dietary supplements, many do not require FDA approval. Currently, there is no standard recommendation for which probiotics to take, how much is needed, and who would most benefit.

The bottom line

Although there is evidence that suggests probiotics may help alleviate digestive symptoms in some people, there is still much to discover about the extent to which taking probiotics is safe and effective for better health. If you are considering taking a probiotic, it is a good idea to consult with your healthcare provider first to make sure it is a safe option for you.