Lactobacillus and Serotonin

There are trillions of bacteria living in our intestines, and the vast majority belong to a group known as Lactobacillus. This is one of many types of probiotic bacteria that colonize our gut microbiome and help us digest food, produce vitamins, regulate immune function and maintain a healthy weight. In addition to these benefits on the inside, Lactobacillus also has an impact on brain health on the outside: it can affect mood! This post will explore the connection between Lactobacillus and Serotonin, and how does this gut microbiome influence your brain.

what is the connection between the gut and the brain?

In the recent years, researchers have been making a lot of progress in understanding the connection between gut bacteria and brain health. There is an emerging field of research that focuses on what’s called the “gut-brain axis.”

The gut-brain axis refers to the communication system, through which information flows from our gastrointestinal tract (GI) to various organs in our body, including the brain.

The gut-brain axis communicates with our brain through the enteric nervous system which is an intricate network of neurons wrapped around the gastrointestinal tract. The main neurotransmitter found in this area of the body is serotonin, a chemical messenger that helps regulate mood and emotional well-being.

There are two ways by which information might be sent to our brains:

Motor nerves stimulate smooth muscles in digestive organs to contract and relax, causing peristalsis (the waves of muscular contraction) that moves food along. This can affect appetite or cause nausea when too much pressure builds up in your stomach from overeating so you vomit what’s left over into your esophagus; Parasympathetic fibers release hormones like acetylcholine, which stimulate the digestive glands to produce saliva and bile, as well as relaxing your stomach muscles so that food can be more easily digested.

what is a lactobacillus bacteria?

Lactobacillus bacteria are probiotic strains that are commonly found in the human gut and vagina. They are Gram-positive, catalase and oxidase negative, nonsporulating bacteria that are rod shaped.

Lactobacillus bacteria can be classified by their many strains: Lb. acidophilus (found in dairy products), Lb. johnsonii (usually found in the mouth or respiratory tract) and Lb. plantarum (most common resident of ileocolonic lymphoid tissue).

The Lactobacillus species can be broken down into short-chain fatty acids (SCFA) and lactic acid. SCFAs are short-chained molecules that can affect the microbiota composition, while lactic acid is a product of fermentation by lactobacillus bacteria in the gut. This lactic acid can help increase the pH of the gut, which is beneficial for probiotic bacteria.

What foods contain lactobacillus?

here are some of the best sources of Lactobacillus:


The probiotics in yogurt can help to improve mood, memory, and cognitive function while they also have a positive effect on your gut flora by increasing the populations of beneficial bacteria like Lactobacillus that produce lactic acid


This fermented dairy drink contains both good and bad strains of Lactobacillus, as well as other types of beneficial bacteria called bifidobacteria (hence the name kefir). Kefirs provide lactic acid to improve digestion in addition to its already long list of benefits for gut health.


This fermented soybean product is a great source of lactic acid. Tempeh contains Lactobacillus bacteria that can improve digestion and promote healthy gut flora, which is essential for overall health.

Miso soup

This soup is already a well-known source of probiotics. Miso provides both good and bad strains of Lactobacillus, bifidobacteria, as well as other types of beneficial bacteria called enterococci.


Pickles are typically made of cucumbers and vinegar. This type of food is a good source for lactobacilli, as well as other types of beneficial bacteria.

Coconut Yogurt Crisps

These sweetened dehydrated coconut chips contain lactobacillus cultures for digestive health benefits; they also provide healthy fats from their coconuts and probiotics from the cultures

Fermented foods

These are rich in lactobacilli, such as fermented vegetables like sauerkraut and kimchi; they also contain healthy bacteria that can improve your gut microbiome. The best way to eat them is either fresh or raw with a little bit of salt

Raw Milk

This unpasteurized milk contains lactic acid produced by live Lactobacillus strains which have been shown to decrease gas production and increase short chain fatty acids, improving overall digestive health

Raw Vegan Cheese

This cheese is made from fermented nut and seed milks. They contain Lactobacillus strains which are helpful for digestion

How does Lactobacillus influence your serotonin levels?

Lactobacillus strains can influence serotonin levels in the brain. The Lactobacillus bacteria are found throughout your digestive tract and live on mucosal surfaces where they protect against pathogen invasion by producing antimicrobial substances, like lactic acid, hydrogen peroxide, and bacteriocins. With help from small molecules called neurotransmitters that regulate mood control systems – including dopamine, serotonine (aka “the happy hormone”), and oxytocin – these natural therapies have an indirect effect on mental health

One of these studies, published in Current Opinion in Clinical Nutrition and Metabolic Care found a “significant association between colonic microbiota composition and central nervous system (CNS) serotonergic activity” as well as an increased risk for depression when comparing people with higher concentrations of lactic acid bacteria to those who have lower concentrations.”

A 2016 study found that bacterial strains from Lactobacillus were able to affect mood regulated signals within the brain region called amygdala.” The sham mice given “live bacteria had significantly increased GABA levels, which created a calming effect, and reduced the levels of stress hormones such as cortisol and adrenaline.

A 2018 study conducted on mice at Florida State University demonstrated how changes to gut microbial communities could affect mood-regulating neurotransmitters. The findings revealed that probiotic use suppresses anxiety behaviors by altering nerve signaling pathways related to GABA receptors. In other words, it changed the way neurons talk to each other within certain regions of the brain.

These findings are not all that surprising because there is a well-established gut-brain connection, as scientists have known for many years now. It’s also been shown in previous animal studies how changes to gut microbes can influence anxiety and depression behaviors by modulating the production of neurotransmitters like serotonin.”

This study demonstrates that probiotics could be a potential new therapeutic tool with the ability to change gut-brain communication and have an effect on mood.


We all know that the brain is a powerful organ, but you may not have considered just how much of an effect bacteria can have on its function. Lactobacillus (a type of probiotic) has been shown to affect serotonin levels in your body and studies are beginning to show this same connection between gut bacteria and mood disorders like depression. If you’re suffering from any kind of mental health issue or simply want to feel better overall, it might be time for some good old fashioned probiotics! We hope this post has been helpful and will provide more information as it becomes available to us. For now, enjoy your meal!