Introduction to Probiotics

Research has shown focusing on improving your gut health may help improve your overall feeling of health and wellness.  From getting frequent colds to feeling groggy and having a hard time concentrating, your gut is intimately connected to the rest of your body.1 

Over the past several years, the medical science community and the public alike have given gut health and probiotics increasing attention. So, what exactly is it about the gut that makes it such a powerful force for our health? Research points to the importance of probiotics, or “good” gut bacteria, for maintaining digestive health and promoting homeostasis (balance) in the rest of the body, from the brain to the immune system. 2,3

Whether you are interested in learning more about probiotics or want to learn about the latest research regarding key probiotic strains proven to improve your gut health, this article will tell you what you need to know and point you to additional sources if you want to learn more. 

What are Probiotics? 

Probiotics are live microorganisms, including bacteria, fungi, and viruses, that live (among other places) in and on the human body and promote our health.1 

Since we are often taught to be afraid of bacteria, fungi, and viruses, it may seem strange if you are learning about probiotics for the first time. However, know that probiotics are not only normal but extremely important for our health. 

Let’s back up a bit 

We’re exposed to bacteria, fungi, and viruses from early development. While we were in the womb, we are exposed to bacteria through our mothers. Through the birthing process and in the first moments of life, we are exposed to more bacteria. As we begin to drink breastmilk or drink from a bottle, and we suck our tiny hands, our intestines continue to be colonised by probiotics forming what is referred to as the gut microbiota. The gut microbiota is the population of microorganisms that live in the digestive system and help maintain homeostasis.3 

While harmless and health-promoting bacteria live on other parts of the body, like the skin and around our genitals, the gut microbiota in the digestive system is the largest population of microorganisms in the human body.4 

Probiotics that live comfortably in our digestive system displace and actively fight against potentially harmful (pathogenic) bacteria to prevent possible damage to our digestive system. Greater microbiota diversity, or a variety of microorganisms comfortably living in our digestive system, is generally associated with a healthy gut and a healthy immune system.4

Key Terms

Probiotics are live microorganisms that live in and on the human body. 1  

Gut microbiota is the community of microorganisms living in the gut. 3   

Prebiotics are nutrients for probiotic microorganisms. They are usually different forms of fiber we eat in our normal diet that our bodies cannot break down.5 

Gut dysbiosis is a microbial imbalance often associated with a lower diversity of gut microorganisms.6 

Gut eubiosis is microbial balance in the digestive system and the main determinant of gut health. 6 

What Types of Microorganisms are Considered Probiotics? 

A variety of microorganisms that are considered probiotics and several have been identified to have specific benefits to an individual’s health. In fact, different types of probiotics have been proven to have specific effects. Here, we provide an overview of different strains of probiotics based on a recent literature review.7 

Genus	Species	Potential Health Benefits
Lactobacillus	L. rhamnosus	– Reduces damage to the lungs caused by the virus – Prevents and reduces the severity of atopic dermatitis in children – Reduces the risk of developing allergies – May have an anti-diabetic potential  – Prevents intestinal infections in children and respiratory infections in newborns  – Help prevent and treat vaginal infections  – Protect large intestinal muscle from damage from lipopolysaccharides
	L. acidophilus	– Helps to treat travelers’ diarrhea – Reduces the hospital stay of children with acute diarrhea – Helps prevent and treat urinary tract and vaginal infections – Reduces IBS symptoms
	L. plantarum	– Anti-fungal properties – Reduces IBS symptoms
	L. casei	– Treats some types of constipation and diarrhea – Supports immune system – Improves symptoms of rheumatoid arthritis – Protects against salmonella infection – Helps prevent some vaginal infections and re-establishes vaginal microbiota
	L. delbrueckii bulgaricus	– Enhances immune system in the elderly – Antibacterial protection from pathogenic E. coli – Supports healthy brain activity
	L. johnsonii	– Helps to support the immune system to protect against respiratory infections – Helps prevent gastritis– Helps treat allergic rhinitis in children
	L. fermentum	– May help reduce insulin resistance and lower cholesterol – Helps prevent and treat vaginal infections
	L. reuteri	– Reduces LDL “bad” cholesterol – Treats some types of intestinal infections in children – Helps manage colic in infants  – Helps strengthen the immune system of preterm newborn babies
Bifidobacterium	B. infantis	– Reduction of IBS symptoms
	B. animalis lactis	– Treats constipation – Prevents urinary tract infections in infants – Reduces total cholesterol  – Reduces risk of upper respiratory tract infections
	B. bifidum	– Reduces total cholesterol – Supports digestive health of children and infants
	B. longum	– Reduces diarrhea – Reduces IBS symptoms – Helps treat gastrointestinal diseases – May help to prevent allergies in newborns
	B. breve	– Reduces cholesterol – Helps prevent and treat serious intestinal infections in infants
Saccharomyces	S. boulardi	– Treats and reduces diarrhea of any cause – Treats IBS – Treats moderate ulcerative colitis – Helps treat acute intestinal infections in children
Lactococcus	L. lactis lactis	– Treatment of diarrhea caused by taking antibiotics – Support vaginal health – Supports healthy brain activity – Fights against pathogenic bacteria
Enterococcus	E. durans	– Anti-inflammatory activity – Antibiotic and antioxidant properties
	E. faecium	– Treatment of diarrhea caused by taking antibiotics
Streptococcus	S. thermophilus	– Reduction of IBS symptoms – Helps prevent and treat serious intestinal infections in infants
Pediococcus	P. acidilactici	– Produces components that actively fight against pathogenic bacteria – Helps eliminate infection with H. pylori, a bacterium that causes chronic gastritis
Leuconostoc	L. mesenteroides	– Produces components that actively fight against pathogenic bacteria
Bacillus	B. coagulans	– Treats antibiotic-associated diarrhea – Supports the immune system – Helps prevent caries (cavities) in children
	B. subtilis	– Treats diarrhea – Fights against H. pylori, a bacterium that causes chronic gastritis

How Do Probiotics Impact My Health?

Considerable research has been done to understand the potential health effects of probiotics. Below, we summarize the research behind seven ways probiotics can improve your health.  

1. Balance Intestinal Microbiome

Several things can cause a person to have intestinal dysbiosis or a poor balance of gut microbiota. We go into detail about what might cause dysbiosis in the next section, but when a person has impaired gut health, it can have a significant negative impact on several aspects of a person’s health and wellness.8 In this case, it may be beneficial for them to undergo probiotic therapy, which is an increase in the intake of probiotics either through diet or, most commonly, through supplements.

People with cirrhosis, a type of liver damage, tend to have intestinal dysbiosis which is associated with a compromised immune system. A randomized, placebo-controlled clinical trial with 58 patients demonstrated that those who took probiotics saw significant improvements in microbiome populations in the gut.9  

Taking probiotics has been shown to improve the intestinal microbiome, which opens the window for a range of therapeutic effects.9,10 

It is important, however, to note that the quality of the probiotic therapy and the type of strain is important. Probiotics are studied and selected based off their strengths and ability to survive the acidic environment to make it to the small intestine to be absorbed.11 

1. Support the Immune System

Gut microflorae have the potential to support the immune system in many ways. Not only does the gut microbiome act as a barrier of defense against pathogenic bacteria by killing them or displacing them, but healthy gut bacteria also regulate immune responsiveness to help the body react appropriately when pathogens or harmful foods are ingested. 

As mentioned before, people with cirrhosis tend to have compromised immune systems, so several clinical trials have examined the effects of probiotics on patients living with this condition. 9 Some studies have encouraged the continued research of probiotics effects on immune health. One example, a placebo-controlled randomised, double blind trial with 80 patients found that probiotic supplementation increased the immune system marker neopterin and the production of reactive oxygen species by neutrophils.12 In addition to potential effects on cirrhosis, another trial with HIV-positive patients undergoing antiretroviral therapy showed improvements in GI tract health and inflammatory response when taking probiotics.13 

These studies suggest that some people with compromised immune systems may benefit from taking probiotics. Even in healthy people, probiotics have been seen to improve antibodies.14 

Remember, however, to speak with your healthcare team before using probiotics as an additional therapy for a condition you may have. It is not currently recommended to attempt to replace any current therapies or medications with any probiotics.  

1. Prevent Allergies

Studies have demonstrated that the administration of probiotics at early stages in life can help to reduce the development of allergic reactions to the environment and foods by normalizing immune and inflammatory responses. 

A randomized, double-blind, placebo-controlled trial demonstrated that the Bifidobacterium lactis strain helped to stabilize the immune response in people who suffer from seasonal allergic rhinitis (SAR), sometimes just referred to as seasonal allergies.15 

Additionally, dysfunction in the intestinal system and skin as a result of an allergenic response can be stabilized by probiotics.16 

1. Reduce Symptoms of Inflammatory Bowel Syndrome

Irritable bowel syndrome (IBS) is a relatively common condition that affects the digestive system. It causes stomach cramps, bloating, diarrhea, and constipation, and there is no cure. Researchers have turned their heads toward probiotics as a potential treatment to help people who suffer from IBS to manage the symptoms.17

A systematic review of twenty controlled trials found that probiotic use was associated with an improvement in overall IBS symptoms compared to a control group, with an especially strong positive effect on abdominal pain.18 

Another systematic review study found that probiotics helped to reduce abdominal distension, bloating, flatulence, and pain associated with IBS.19 

While early data looks promising, researchers suggest medical teams be cautious when evaluating the potential of recommending the use of probiotics for treatment, due to a variety of limitations with current research. 

1. Reduce Cholesterol 

For the last several decades, researchers have examined the effects of probiotics as a non-pharmacological treatment for reducing cholesterol. 

A recent systematic review found that in people with high cholesterol when compared to control groups, those who took probiotics may experience significant reductions in total serum cholesterol. However, researchers found neither strain type nor dose of probiotic influenced total cholesterol. This suggests supplementing with any probiotic may help lower total cholesterol.20

Effects may be improved if probiotics are taken with prebiotics, though data on this is still limited. 5

1. Treat Diarrhea and Constipation

The digestive effects of probiotics are perhaps one of the better-known positive effects they can have on human health. 

Whether because of the introduction of new bacteria strains into the intestinal environment (like what happens when you travel), acute infection, or in the aftermath of antibiotic treatment, there is solid proof that, in addition to rehydration, taking probiotics can help to treat diarrhea in children and adults.21

Clinical trials have demonstrated that taking probiotics can help to manage digestive issues in pregnant women and even in infants.22,23 However, remember to consult with your healthcare team before taking them if you have a special condition or giving them to your young children.

Additionally, probiotics can help to treat constipation.24 Systematic reviews have demonstrated that in adults, probiotics can help to improve transit time, stool frequency, and stool consistency. 

1. Support Brain Health

It may seem strange that the population of bacteria in your gut can affect your brain health. However, this is not a new concept and has been demonstrated repeatedly for decades.25 Through what is referred to as the gut-brain axis, the gut microbiota impacts immune activation, intestinal permeability, hormone signaling, and other factors that all impact nervous system signaling.26

Research has demonstrated that dysbiosis, or an imbalance in gut microbiota, is associated with a range of nervous system disorders, including autism, anxiety, depression, and even Alzheimer’s disease.27 

What Factors Might Negatively Impact My Gut Microbiota? 

Several factors in the short and long run may impact your gut microbiota. 

Some of these include: 

• Taking certain medications, especially antibiotics
• Current infection or other health condition
• Genetics and factors related to the host (you)
• Autoimmune diseases
• Eating habits, sleep, and exercise
• Stress
• Age
• Taking probiotic and prebiotic supplements 

Several factors impact our gut microbiota that we cannot control, like autoimmune diseases, age, health conditions, and genetics. However, factors like exercise, eating habits, stress management, sleeping enough, and taking probiotic supplements can improve your gut microbiota. 

What is the Relationship Between Probiotics and Prebiotics?

Probiotics are the live microorganisms that live in and on the body. Those that live in the intestinal system compose the gut microbiota. Like all living things, the gut microbiota needs a source of energy and nutrients. The “food” that probiotics need to survive and thrive is what we call prebiotics. 

What are prebiotics exactly? In short, prebiotics are components that we eat but cannot digest, like dietary fiber. When probiotics find that they have plenty of food in their environment, they are more likely to stay put and reproduce in your gut so that they can get to work keeping pathogenic bacteria out, promoting hormonal health, and so much more. 5 

Prebiotics can be obtained through eating fiber-rich foods like fruits, vegetables, and whole grains, or through taking probiotic supplements with prebiotics. Taking prebiotic supplements is a good option if, due to health reasons like IBS, individuals tend to have reduced fiber intake. 28 

How Can I Have a Healthier Gut Microbiota?

Get Plenty of Exercise

Exercise has multiple benefits for your health and wellbeing, from reducing stress to improving blood pressure and blood glucose. Researchers have found that exercise has a direct impact on gut microbiota as well.29

One of the ways in which exercise can influence gut microbiota is by influencing the transit time of food through the intestine. When we do not exercise, transit time takes longer, and there is a longer contact time between pathogens we have ingested and the gastrointestinal mucus layer. These pathogens may directly attack gut microbiota and infect the intestine. Additionally, exercise has an anti-inflammatory action on the gut, which favors microbiome development.30 

Sleep and Rest

Sleep deprivation and poor sleep quality can disrupt multiple hormonal and metabolic systems in the body. These changes have a negative impact on the gut microbiota population.31 

While one or two nights of poor sleep will unlikely impact your gut microbiota, chronic poor sleep and rest can. Getting longer, better-quality sleep can have significant positive effects on your gut microbiome.32 

Through What You Eat and Drink

Diet is one of the most influential environmental factors that impact gut microbiota. Through diet, your body is introduced to probiotics and prebiotics, and to nutrients that help to support healthy gut environments.33 

Some of the foods that can promote a healthy gut microbiome include: 

• Probiotic-containing foods, like yogurt, kefir, cheese, kombucha, miso soup, sauerkraut, tempeh, and pickles. 
• Prebiotic-containing foods, like fruits and vegetables and whole grains. 
• Foods with anti-inflammatory components, like fruits and vegetables, fish, and whole grains. 

In general, you want to eat more of the foods above, and less ultra-processed foods and foods high in refined sugar to promote gut health. 

Through Supplements

One of the most effective ways to improve your gut microbiome is through taking probiotic supplements. When a person has probable or proven microbiota imbalance, probiotic supplements are often a therapeutic option. Probiotic supplementation may also help to reduce the risk of different conditions associated with microbiota imbalance. 34 

The advantage of probiotic supplements is that they can be formulated with specific strains demonstrated to have proven therapeutic effects and they can be packaged in a way to improve their survival in the digestive system. 

In healthy people, probiotic and prebiotic supplementation is safe and effective, and they can be purchased without prescriptions. 35  

Main Takeaways

Probiotics are an essential part of overall health and wellbeing. While they are best known for their positive impact on gut health, probiotics can help to improve brain health, metabolic health, and much more. 

While several factors influence your gut health that are out of your control, you can support your gut microbiota by eating a balanced and diverse diet rich in fiber and fermented foods, exercising regularly, sleeping enough, and taking probiotic supplements.

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Sasha Aparicio