Gut Health

Evidence based

Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of licensed nutritionists and dietitians strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.

Why Take Probiotics?

Written by Dr. Michael Ruscio, DC on March 21, 2020

Written by Dr. Michael Ruscio, DC on March 21, 2020 — Reviewed by Noora Alakulppi

• What Are Probiotics|
• How They Work|
• Gut Health|
• Digestive Conditions|
• Mood|
• Infections|
• Sleep|
• Intolerance & Allergy|
• Brain Fog & Cognition|
• Hormonal Health|
• Autoimmunity|
• Metabolic Health|
• Conclusion|

12 Health Conditions that Probiotics Can Help

Taking daily probiotic supplements may be one of the simplest and most effective ways to improve both your gut health and your overall well being.

The gut is arguably the leading source of inflammation in your body. That’s because your digestive tract is the front line for your immune system with the greatest density of immune cells in your body.^[1]  Digestive health challenges, inflammatory health conditions, food intolerances and even mystery symptoms like fatigue and brain fog are often signs that your gut health isn’t optimal.

Said simply, your gut health is at the core of your well-being.

The good bacteria in probiotic supplements can help to restore your digestive health, leading to less inflammation, better nutrient absorption, and better overall health. More than 500 research trials show that probiotics have wide-ranging benefits for human health.

Here’s a summary of the growing body of research evidence for probiotics:

What are Probiotics?

Most people have upwards of a thousand different live bacteria species living in their gut. This colony of live microorganisms is known as the microbiota or microbiome. 

Probiotics are those microorganisms that provide health benefits to their host. We co-evolved with good bacteria in a symbiotic relationship where we help them and they help us. 

Probiotic supplements provide extra beneficial bacteria that may be lacking when your gut health is out of balance. Most strains of probiotic supplements don’t actually colonize your digestive tract. However, they do increase the health and bacterial diversity of your microbiome and have many other health benefits too.

These live microorganisms can also be found in probiotic foods like sauerkraut, kefir, kimchi, and kombucha.  A variety of probiotics can be found in these foods such as:

• Lactobacillus, including lactobacillus acidophilus
• Bifidobacterium species
• Saccharomyces boulardii

How Do Probiotic Supplements Help You? 

The Journal of Clinical Gastroenterology^[2] and the journal Trends in Microbiology^[3] offer insights regarding how probiotic bacteria can make you healthier.

Probiotics can:

• Increase bacterial diversity, or health, of your microbiome^[4]
• Fight pathogens (harmful bugs) and their toxins
• Promote more rapid recovery from imbalances in your gut bacteria
• Promote a healthy immune system response in your digestive tract^{[5, 6]}
• Reduce gut inflammation (remember excessive inflammation is part of an overzealous immune response)^[7]
• Encourage the growth of healthy bacteria in your gut^[8]
• Reduce leaky gut aka damage to your gut lining^{[9, 10, 11]}

An important point to emphasize is that probiotic supplements are antibacterial, antifungal and antiparasitic. This is, in part, how they help promote a healthier community of live microorganisms in your digestive system, they clean out the bad bugs. 

The Far-Reaching Impact of Your Gut Health

When you understand the connections between your gut health, your immune system, inflammation, and nutrient absorption, it’s easier to appreciate the far-reaching impact your gut health has.

Immune System

Poor gut health (including poor bacterial balance) can lead to an overzealous immune system response. This is in part because the largest density of immune cells in your body resides in your small intestine^[12].  Meaning your digestive tract has a major impact on your immune system.    

Inflammation

An overzealous immune system produces high levels of inflammation.  This inflammation causes numerous problems, most disease has an inflammatory component.   

Nutrient Absorption

You are what you eat but also what you absorb.    Inflammation can damage the lining of the digestive system, which then impedes nutrient absorption. This is how certain gut therapies have been shown to improve nutrient absorption^[13].  If you are eating a healthy diet but not adequately absorbing the nutrients, it can be similar to eating an unhealthy diet.

Probiotics Can Treat Digestive Imbalances

Significant research shows that probiotic supplements are an effective treatment for symptoms of irritable bowel syndrome (IBS), including constipation, bloating, loose stools, diarrhea, abdominal pain, and gas.^{[14, 15, 16]} The Canadian Association of Gastroenterology recommends a trial on probiotics in their guidelines for IBS patients.^[17]

Probiotics have also been shown to be effective for treating small intestinal bacterial overgrowth (SIBO), both in improving symptoms and in improving lab values.^{[18, 19, 20]} One study found probiotic supplements to be more effective for SIBO when compared directly to standard antibiotic treatment.^[21]

Two studies show that probiotics help to promote intestinal repair in those with leaky gut.^{[22, 23]}

We also have evidence showing that probiotic supplements are antifungal and antiparasitic. One study shows that probiotics are as effective as antifungal drugs for treating fungi.^[24] Two more studies show that probiotics have benefits in the treatment of Giardia and Blastocystis hominis infections (both caused by protozoa). ^{[25, 26]}

Several research reviews have shown probiotics to be helpful for inflammatory bowel disease (IBD), including Crohn’s disease and colitis, both on their own and used together with anti-inflammatory drugs.^{[27, 28, 29, 30]}  One further review draws a different conclusion and finds that probiotics do not help maintain remission.^[31]

The prestigious Journal of the American Medical Association published a meta-analysis of 82 clinical trials and found that probiotic supplements help to prevent and treat antibiotic-associated diarrhea.^[32]

Probiotics Help Mood, Depression & Anxiety

Your gut health has a big impact on mood. For example, we know when there is inflammation in the digestive system, it can also cause inflammation in the brain, potentially leading to symptoms like depression and anxiety.

One meta-analysis of 10 clinical trials found that probiotic supplements led to significant improvements in the moods of individuals with mild to moderate depressive symptoms and non-significant effects on mood in healthy individuals.^[33]

Another meta-analysis of clinical trials found probiotics led to a significant reduction in depression.^[34]

There is also data showing anxiety can be improved from probiotic supplements.  The data here are not as strong, but still have shown an anti-anxiety effect, in human clinical trials.^[35]

Probiotics Fight Infections

In addition to helping with digestive tract infections, probiotics have also been shown to both prevent and treat other types of infections. Significant evidence suggests that:

• Probiotic consumption decreases the incidence of respiratory tract infections in children.^[36]
• Probiotics may be helpful in preventing recurrent urinary tract infections in women.^[37]
• Probiotic supplements are safe and beneficial for the treatment of vaginal infections.^[38]
• Probiotics decrease oral pathogens that cause cavities, gingivitis, and periodontal disease and may be beneficial for the maintenance of oral health.^[39]

Probiotics Improve Sleep

In a clinical trial of medical students, those who took probiotic supplements showed superior sleep quality during times of exam stress.^[40]

In another clinical trial, participants reported that their sleep quality improved after 6 weeks of taking probiotics.^[41]

A clinical trial of IBS patients showed sleep improvements for diarrhea-type IBS patients. The same results were not seen for constipation-type mixed-type IBS patients.^[42]

Finally, a study of subjects with depression showed that the group taking probiotic supplements had less sleep disruption than the placebo group.^[43]

Probiotics Can Improve Food Intolerance and Seasonal Allergy

Good news for dairy lovers!  A systematic review of 15 clinical trials found that probiotics can improve dairy tolerance.^[44]

A meta-analysis of 22 randomized control trials concluded that probiotics can improve seasonal allergies.^[45]   Other high-quality studies support this same finding.^[46] 

There is also data, albeit mixed, suggesting that probiotic supplements given to children may prevent or reduce the formation of allergy.^[47]

Probiotics May Help with Brain Fog and Cognition

Data for brain fog are preliminary but encouraging, especially for those with IBS.^[48]  Probiotics have improved cognition in patients with:

• Alzheimer’s^{[49, 50]}
• Bipolar disorder^[51]
• Fibromyalgia^[52]

Hormonal Health and Probiotics

Thyroid Function

Two studies suggest a correlation between hypothyroid/thyroid autoimmunity and SIBO.^{[53, 54]}  A recent meta-analysis (summary of clinical trials) also finds an association between the bacteria H. pylori and thyroid autoimmunity.^[55] 

Since we know that probiotic supplements can be effective for treating gut imbalances like SIBO and H. pylori overgrowth, it’s plausible that probiotic supplements may be helpful for those with low thyroid function.

Female Hormones

We don’t have good data regarding female hormones and probiotics, but we can make some inferences based on other research.

Research shows that gut dysbiosis can disturb estrogen levels^[56] and that women’s health conditions associated with unbalanced estrogen levels (for example: PCOS, obesity, endometriosis, cardiovascular disease, and breast cancer) are associated with low bacterial diversity in the digestive tract.^[57]

One very recent meta-analysis confirms that we are on the right path with these inferences.^[58] The authors looked at 13 studies involving 855 women diagnosed with PCOS and found that probiotic supplements improved hormonal and inflammatory markers for these women.

Probiotics May Help with Autoimmunity

While data is sparse for autoimmunity, the findings we do have are encouraging.

Early probiotic supplementation (in the first 27 days after birth) was shown to reduce the risk of type 1 diabetes in children when compared to children who had not taken probiotics after birth.^[59]

Another study found that probiotic supplements can result in positive outcomes for patients with multiple sclerosis.^[60]

Three different studies found mixed results for rheumatoid arthritis. One study did not show significant improvement with probiotic supplements while two other studies did show improvements.^{[61, 62, 63]}

One research review noted that intestinal dysbiosis is common in those with autoimmune disease.^[64]

Probiotics Show Minor Improvements for Metabolic Health

The data mostly show small improvements for weight loss and improving cholesterol, blood pressure and blood sugar levels.^{[65, 66, 67, 68, 69]} Probiotics should not be viewed as the primary therapy for these conditions.

In Conclusion

Based on the evidence to date, there are plenty of good reasons to take probiotics, whether for all the benefits of good gut health or to address specific symptoms and health conditions. Research into the benefits of probiotic supplements is only in its infancy and the next few years are sure to bring more exciting discoveries. In the meantime, there are plenty of good reasons to take probiotics now.

Keep in mind that the best probiotics are not necessarily the most expensive supplements you can buy. However, you should always check that your probiotic supplement has had independent lab testing. This ensures that your probiotic actually contains the same probiotic strains and number of colony-forming units (CFUs) as stated on the label. It also ensures that your probiotic supplement is not contaminated with harmful organisms.

Some practitioners may recommend taking specially coated probiotics to protect the live organisms from the stomach acid in your digestive tract. Or they may suggest taking supplementary prebiotics or high levels of prebiotic foods to feed your beneficial bacteria. Based on my research and clinical experience, most people don’t need these extra steps to benefit from a probiotic supplement. I recommend keeping it simple and just taking probiotics along with your healthy diet.