Probiotics are being touted as a cure-all for everything from weight loss to dental cavities. In this article we will review the research and evidence for the benefits of probiotics.
What are the Proven Health Benefits of Probiotics?
While probiotics may be very useful for some health benefits, they may not be for others. For example, probiotics can help tremendously with diarrhea and acne; however, they have limitations regards to weight loss. Read more below to learn what probiotics can actually help with.
Why Take Probiotics?
There are number reasons why people use probiotics. Let's see which ones have enough evidence to back them up. ✅ means that research has shown good results for this use and ❌ means research hasn't shown this.
Probiotic Dosing Chart
|Number of Studies in Meta-Study||Median Probiotic Dosage (billion CFUs/day)||Benefit found|
|Diarrhea||34||6||Reduced antibiotic associated diarrhea by 52%, traveler’s diarrhea by 8%, and acute diarrhea due to diverse causes by 34%|
|Constipation||15||6.5||Decreased the gastrointestinal transit time, increased the number of bowel movements, and improved stool consistency|
|H. pylori Ulcers||10||1.26||Adding probiotics to traditional antibiotic treatment doubled the eradication odds of H. pylori (eradication odds ratio = 2.066)|
|C diff||6||20||Probiotics lowered the relative risk of developing C diff by 41% compared to placebo|
|IBS||17||1.2||Improved IBS symptoms in 29% of patients|
Probiotics for Diarrhea (Traveler's Diarrhea, Antibiotic Associated Diarrhea, and Acute Diarrhea with Diverse Causes) ✅
Probiotics have long been used for the treatment and prevention of diarrhea. Acute onset, rather than chronic, diarrhea is often infectious and can spread rapidly among affected populations.10 These cases of diarrhea usually have diverse causes. One study found that a minimum dosage of 10 billion CFUs is required to reduce the duration of diarrhea more than one-half a day.16
A high powered meta-study of 34 other studies published in the prestigious journal The Lancet found that a median dose of 6.0 billion CFUs/day was able to significantly reduce antibiotic associated diarrhea by 52%, traveler’s diarrhea by 8%, and acute diarrhea due to diverse causes by 34%.25
Probiotics for Constipation ✅
The use of probiotics can help soften stools and normalize bowel movements. A meta-study or "study of studies" of 16 other studies found that a median dose of 6.5 billion CFUs/day of probiotics increased the gastrointestinal transit time, number of bowel movements, and stool consistency.9
Probiotics for H. pylori Ulcer Treatment ✅
H. pylori is the causative agent of stomach and duodenal ulcers. Treatment usually involves triple antibiotic therapy and a proton pump inhibitor (PPI). A review article that looked at pooled data from 10 other studies comparing the eradication of H. pylori using traditional treatments with and without probiotics found that adding a median dose of 1.26 billion CFUs/day of probiotics to traditional treatment doubled the eradication odds of H. pylori (eradication odds ratio = 2.066).17
Antibiotic Associated Diarrhea, Probiotics for C diff ✅
When you are diagnosed with a bacterial infection, your doctor is likely to prescribe antibiotics. Antibiotics may eradicate an infection, but they may also kill off good bacteria at the same time, and that often leads to antibiotic associated diarrhea (AAD). Studies have shown that taking probiotics during and after antibiotic therapy can reduce the incidence of diarrhea. To ensure the antibiotics don’t kill off the probiotics, consume the probiotics a few hours after taking your antibiotic.2
C diff infections are an extreme form of antibiotic-associated diarrhea (AAD). It happens when your microbiome has been so disrupted by antibiotics that the bacteria Clostridium difficile has no competition and is able to take over the gut and release toxins that cause diarrhea. It often occur after taking broad spectrum antibiotics to treat some other type of infections.
As a result of taking antibiotics the good bacteria in the gut are killed off by the medication, allowing C diff to proliferate. Symptoms include fever, cramping, and diarrhea. The resulting dehydration that can cause serious illness. Taking probiotics can replenish the healthy gut bacteria and help prevent reoccurrences of C diff.
A high powered meta-analysis published in the prestigious journal Nature analyzed multiple randomized controlled trials (RCTs) and found 6 that were done well enough to conclude that probiotics can lower the relative risk of developing C diff by 41% compared to placebo. These studies had a median dose of 20 billion CFUs/day. In terms of probiotic strains the studies found that while Lactobacillus probiotics were helpful in lowering the incidence of Antibiotic Associated Diarrhea only the probiotic Saccharomyces boulardii was helpful in preventing the reoccurrence of C diff.24
Probiotics for IBS ✅
Irritable bowel syndrome results in chronic digestive disorders, which present themselves as either diarrhea or constipation. IBS is caused by a hypersposmadic gut and inflammation plays a role in causing the hypersposmadic state. A meta-analysis, or study of studies, found that at a median dose of 1.2 billion CFUs/day probiotics improved IBS symptoms in 29% of patients.18 This meta-study analyzed data from 18 different studies (we have excluded 1 from the median dose calculation because dosing was not disclosed in that study). You can read more about the role of probiotics in IBS here.
Probiotics for Inflammatory Bowel Disease IBD (Ulcerative Colitis/Crohn’s Disease) ❌
One meta-analysis found that administration of probiotics improved the remission rates in ulcerative colitis. Probiotic administration did not improve remission of Crohn’s disease, and pouchitis.19
Probiotics for Acne ✅
Acne is closely linked to diet and food choices. Being depressed, anxious, or stressed can cause you to make poor dietary choices. Some studies have reported benefits when taking probiotics for acne. However, there are no high powered studies at this time. Probiotics may help acne by reducing inflammation and improving mood. For more information read our article on diet and acne.
Probiotics for Mood – Anxiety and Stress ✅
Levels of anxiety and stress is correlated with the production of pro-inflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), IL-1 receptor antagonist (IL-1Ra), interferon γ (IFN-γ) and IL-10.20 Probiotics interact with the immune system and can lower the production of stress cytokines. Several studies2 show that consumption of probiotics over six weeks or more can reduce depression and anxiety. For more read our article on probiotics and their effect on stress, anxiety, and mood.
Probiotics for Allergies and Eczema ✅
The use of Lactobacillus rhamnosus by pregnant mothers prenantally and by infants post-natally for 6 months found that incidences of atopic eczema was reduced in half in the groups given Lactobacillus rhamnosus (23% vs 46%).12 These findings were corroborated in follow-up and additional studies.21
Probiotics for Weight Loss ❌
Taking probiotics for weight loss is a new idea. Studies show that probiotic makeup of the gut is influenced by diet. It is also true that probiotics can influence dietary choices and metabolism.11 Several things have been observed at this point. The first is that obesity is associated with reduction in Bacteroides probiotics and an increase in Firmicutes. Microbiomes in obese individuals are also less diverse compared to non-obese individuals.23 More studies are needed.
Probiotics for Vaginal Infections - Bacterial Vaginosis, Yeast, and UTIs ✅
In healthy women there are Lactobacilli that keep the pH in the vagina low and prevent the overgrowth of microbes that can cause BV, yeast infections, or UTIs. Disruption of the vaginal flora or dysbiosis of the vaginal flora is common after taking antibiotics because antibiotics disrupt the microbes that normally reside in the vagina. Probiotics taken orally do end up colonizing the vagina.22 Read more about the role of probiotics for BV and yeast infections.
Our Response to the Recent Study on Probiotics
A study published in Cell on September 6th, 2018 claims that probiotics have no benefits.13 The study looked at colonization of the gut following administration of an 11-probiotic blend consisting of B. bifidum, L. rhamnosus, L. lactis, L. casei, B. breve, S. thermophilus, B. longum sbsp. longum, L. paracasei, L. plantarum and B. longum sbsp. Infantis and found that the probiotics did not colonize or take up residence in the gut. The logic is that if the probiotics do not take up residence in the gut then probiotics provide no benefits.
This study has several flaws.
- Colonization of the gut is only one way to measure the efficacy of probiotics. Better ways include actual disease states and outcomes.
- Colonization is not necessary for probiotics to provide benefits. For example, the probiotic Saccharomyces boulardii does not actually colonize the gut. It passes through the digestive tract yet is still able to elicit immune modulating effects and reduce the duration of diarrhea.
- The study was done on healthy volunteers and excluded persons who have been on antibiotics within the past 3 months. People who have recently been on antibiotics are the people who need probiotics the most as they suffer from dysbiosis or disruption of the gut flora. The study also excluded subjects with a chronic gastrointestinal disorder such as Irritable Bowel Syndrome (IBS) or Inflammatory Bowel Disease (IBD). Arguably, these are the subjects that would benefit the most from probiotics, not healthy individuals.
A follow-up study15 by the same authors examined the microbiome of individuals who took antibiotics and compared it to their pre-antibiotic state. One group took the same probiotic combination used in the first study after antibiotic use. The second group took their own fecal matter that was collected before the round of antibiotics in a sort of autologous fecal microbiota transplant (FMT) and the third group utilized a wait-and see approach.
All groups experienced microbiome disruption. The FMT group did restore their microbiome to the pre-antibiotic state rapidly as expected. The wait-and-see group eventually was able to return to their pre-antibiotic state within 21 days. The probiotic treated group became colonized by the probiotics and did not return their microbiome to the pre-antibiotic state.
The authors argued that that the pre-antibiotic state is natural and “best” and were surprised that the microbiome of the group that took antibiotics followed by antibiotics never reverted back to their original microbiome. They argued that this alteration of the “natural” microbiome was bad which may not be necessarily true.
The microbiome is unique and developed as the result of exposure to different foods and life experiences. As seen in our article on the hygiene hypothesis the modern diet has resulted in a greater incidences of atopic (allergic) diseases such as eczema, allergies, and asthma. Certain microbiomes are also associated with obesity.14 Research into the effects of consuming probiotic strains used in the studies have demonstrated numerous benefits that were reviewed above.
How Long Does It Take for Probiotics to Work?
Taking a probiotic isn’t like taking a medication designed to work within a certain period of time. How long it takes these microorganisms to make a noticeable difference depends upon the type of probiotic and the gut condition of the user. It can take several days to a few weeks before noticing the benefits of probiotics. It really depends on the level of dysbiosis you have as well as the results you are trying to achieve.
- https://www.ncbi.nlm.nih.gov/pmc/articl es/PMC4045285/