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Probiotics and Gut Health

The human microbiota is a complex ecosystem within our gut containing trillions of microbes, which has been shown to play a crucial role in our health and wellbeing. Among these microbes are probiotics. Probiotics are beneficial bacteria that confer health benefits when consumed in adequate amounts. Lets look into the intricate relationship between probiotics and gut health, exploring the evidence supporting their role in promoting a healthy gastrointestinal system.

Woman with stomach ache. Lying on her bed holding her stomach.

Understanding Probiotics

Probiotics, often referred to as 'good' or 'friendly' bacteria, are found in various foods, including fermented foods like yogurt, sauerkraut, and kombucha, as well as in dietary supplements. The most common types of probiotics are Lactobacillus and Bifidobacterium species, but others, such as Saccharomyces boulardii, a type of yeast, are also used. These probiotics contribute to various health benefits, ranging from supporting digestive health and enhancing the immune system to potentially alleviating conditions like irritable bowel syndrome (IBS) and antibiotic-associated diarrhea (AAD).

Probiotics and Gut Health

The gut microbiota is involved in many essential functions, including nutrient absorption, vitamin production, and immune system regulation. When the gut microbiota is balanced, it promotes health, but various factors can disrupt this balance, leading to dysbiosis. Dysbiosis has been associated with numerous health issues, including obesity, autoimmune diseases, and even mental health disorders such as anxiety and depression.

Probiotics help restore this balance. They compete with harmful bacteria for nutrition and attachment sites, produce antimicrobial substances, and modulate immune responses. Through these mechanisms, probiotics help maintain the gut barrier's integrity, preventing harmful substances from leaking into the body, a phenomenon known as 'leaky gut' (Camilleri, 2019).

Clinical Evidence

Numerous studies support the role of probiotics in managing gut-related disorders. A systematic review and meta-analysis of 37 randomised controlled trials found that certain strains of Bifidobacterium and Lactobacillus effectively reduced overall IBS symptoms and abdominal pain (Ford et al., 2014). Another meta-analysis involving nearly 12,000 participants across 63 studies found that probiotics significantly reduced the risk of AAD (Hempel et al., 2012).

In terms of mental health, a review of 15 human studies found that taking probiotics for 1–2 months can improve symptoms of depression and anxiety (Wang et al., 2016). This evidence supports the concept of the gut-brain axis, where the gut microbiota can influence brain health and behaviour.

However, it's important to note that not all probiotics are the same. Different strains have different effects, and what works for one person might not work for another. Emerging research in the field of personalised probiotics, tailored to the individual's gut microbiota, is promising and could offer more targeted and effective treatments in the future (Zmora et al., 2018).

The role of probiotics extends beyond the gut to other areas of the body. Emerging research suggests that gut health impacts cardiovascular health, brain function, and even skin conditions. For instance, a study in the journal ‘Nature’ highlighted that a specific strain of Lactobacillus reuteri could reduce cholesterol levels in mice, suggesting a potential role for probiotics in heart health (Kumar et al., 2012).

Additionally, the gut-brain axis, a bi-directional communication pathway between the gut and the brain, has attracted significant research attention. A systematic review published in ‘Translational Psychiatry’ showed that probiotics could have beneficial effects on mood, anxiety, and cognitive symptoms, further emphasising the importance of a healthy gut microbiota for mental health (Huang et al., 2019).

The skin, our body's largest organ, is also influenced by gut health. Research suggests that probiotics could be beneficial for various skin conditions, including acne and eczema. A review in the 'American Journal of Clinical Dermatology' highlighted that oral and topical probiotics show promise in the treatment and prevention of these skin conditions (Levkovich et al., 2013).

Probiotic Safety and Considerations

Generally, probiotics are considered safe for most people. However, in people with weakened immune systems or serious illnesses, probiotics could theoretically lead to dangerous infections. Furthermore, some people might experience mild side effects like gas and bloating.

*Always consult with a professional before taking medications or supplements.*

Interesting Information


is a genus of bacteria that belongs to the lactic acid bacteria (LAB) group. It is a diverse group of bacteria that includes various species, many of which are naturally found in the human body, particularly in the gastrointestinal tract, mouth, and vagina.

Lactobacillus bacteria are known for their ability to ferment sugars and produce lactic acid as a metabolic byproduct. This acidification process gives them the ability to survive in acidic environments, such as the stomach and the vagina, where they help maintain a healthy microbial balance.

There are many species of Lactobacillus, and some of the commonly known ones include Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus, and Lactobacillus plantarum. These bacteria have been extensively studied for their potential health benefits, particularly in supporting digestive health and immune function.

Lactobacillus species are commonly used in the production of fermented foods such as yogurt, kefir, and sauerkraut. They are also available as probiotic supplements, which are consumed to introduce beneficial bacteria into the gut and promote a healthy gut microbiota.


is another genus of bacteria that falls under the lactic acid bacteria (LAB) group. Like Lactobacillus, Bifidobacterium species are beneficial bacteria that are commonly found in the human gastrointestinal tract, particularly in the large intestine.

Bifidobacterium bacteria are anaerobic, meaning they thrive in environments with low levels of oxygen. They are known for their ability to ferment carbohydrates and produce lactic acid, acetic acid, and other beneficial compounds. These bacteria play a crucial role in maintaining the balance of the gut microbiota and supporting various aspects of human health.

Bifidobacterium species have been extensively studied for their potential health benefits, particularly in relation to digestive health, immune function, and overall well-being. They are believed to contribute to the breakdown and absorption of nutrients, provide a protective effect against harmful bacteria, modulate the immune system, and support a healthy gut barrier function.

Similar to Lactobacillus, Bifidobacterium species are commonly used in the production of fermented foods and are also available as probiotic supplements. These supplements are designed to deliver live and beneficial bacteria directly to the gut, promoting a healthy gut microbiota.

Saccharomyces boulardii

is a beneficial yeast that is often used as a probiotic supplement. It is classified as a non-pathogenic yeast and is distinct from the Saccharomyces cerevisiae yeast commonly used in baking and brewing.

Saccharomyces boulardii is derived from a tropical fruit called lychee and was initially isolated by a French scientist named Henri Boulard. It has been extensively studied for its potential health benefits, particularly in supporting digestive health and combating gastrointestinal issues.

Unlike bacteria-based probiotics like Lactobacillus and Bifidobacterium, Saccharomyces boulardii is a yeast that acts as a probiotic in the gut. It has several mechanisms of action that contribute to its beneficial effects. It can help restore the balance of gut microbiota by inhibiting the growth of harmful bacteria and promoting the growth of beneficial bacteria.

Saccharomyces boulardii has been shown to be effective in reducing the risk and severity of antibiotic-associated diarrhea, Clostridium difficile infection, and traveler's diarrhea. It may also help alleviate symptoms of inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), and other gastrointestinal conditions.

Additionally, Saccharomyces boulardii has been reported to have immunomodulatory effects, meaning it can influence the immune system in a way that promotes a healthy immune response. It may help regulate the production of inflammatory compounds and strengthen the gut barrier function.

Lactobacillus reuteri

is a species of bacteria that belongs to the Lactobacillus genus. It is naturally found in the gastrointestinal tract of humans and animals, as well as in some fermented foods and dairy products.

Lactobacillus reuteri is a lactic acid-producing bacteria, meaning it can ferment sugars and produce lactic acid as a metabolic byproduct. This acidification process helps create an environment in the gut that is unfavourable for the growth of harmful bacteria, thereby promoting a healthy microbial balance.

Bibliography and interesting studies

Hill, C., Guarner, F., Reid, G., Gibson, G. R., Merenstein, D. J., Pot, B., Morelli, L., Canani, R. B., Flint, H. J., Salminen, S., Calder, P. C., & Sanders, M. E. (2014). Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology, 11(8), 506–514.

McFarland, L. V., & Dublin, S. (2010). Meta-analysis of probiotics for the treatment of irritable bowel syndrome. World Journal of Gastroenterology, 16(17), 1908-1915.

Szajewska, H., & Kołodziej, M. (2015). Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Alimentary Pharmacology & Therapeutics, 42(7), 793-801.

Zhang, Y. J., Li, S., Gan, R. Y., Zhou, T., Xu, D. P., & Li, H. B. (2015). Impacts of gut bacteria on human health and diseases. International Journal of Molecular Sciences, 16(4), 7493-7519.

Ford, A. C., et al. (2014). Efficacy of prebiotics, probiotics, and synbiotics in irritable bowel syndrome and chronic idiopathic constipation: systematic review and meta-analysis. The American Journal of Gastroenterology, 109(10), 1547-1561. doi: 10.1038/ajg.2014.202

Hempel, S., et al. (2012). Probiotics for the prevention and treatment of antibiotic-associated diarrhea: a systematic review and meta-analysis. JAMA, 307(18), 1959-1969. doi: 10.1001/jama.2012.3507

Kumar, M., et al. (2012). Lactobacillus reuteri NCIMB 30242 increases mean circulating LDL cholesterol: a randomized, double-blind, placebo-controlled study. Atherosclerosis, 221(2), 414-419. doi: 10.1016/j.atherosclerosis.2012.01.006

Huang, R., et al. (2019). Effect of probiotics on depression: a systematic review and meta-analysis of randomized controlled trials. Translational Psychiatry, 9(1), 1-11. doi: 10.1038/s41398-019-0555-9

Levkovich, T., et al. (2013). Probiotic bacteria induce a 'glow of health'. PLoS ONE, 8(1), e53867. doi: 10.1371/journal.pone.0053867

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