Key Topics Covered
What are probiotics?
Probiotics are live microorganisms that can be consumed through food or supplements, that are promoted to improve health.
We will just be talking about supplemental form in this podcast.
How could they theoretically help?
Theoretically, they could help with anything that gut health plays a role in. It is super broad.
- IBS symptoms in general
- Specific causes of IBS flare-ups or symptoms (e.g. antibiotics or travelling)
- Mental health
- Body composition
- Immune function
- Heart health
- Inflammatory bowel disease
- Other conditions such as allergies and eczema
The list can be endless. Probiotics can be theoretically linked with all these things. But they may or may not actually help.
Strain Specificity
Not all probiotics are the same. Different strains have different functions in the body. And different products have different amounts of these strains.
Theoretically, you should be choosing a strain that is ideal for your specific situation.
But how do YOU know which one is ideal for you?
Adding to that challenge is that the research isn’t really at a point where things are clear.
Some studies show benefits. Others don’t. But they almost all use varying strains and dosages.
Ideally, we would have research showing X strain or strains at Y dosage improves Z condition. And then there would be a bunch of similar research replicating that with minor modifications until we find the optimal protocol. But at this stage, that replication is mostly missing.
IBS Symptoms
- The research on IBS is the best example of what we are talking about. It is the most studied area of probiotic research.
- A 2016 review on probiotics and IBS found that of 29 studies assessed, 14 showed improvements.
- So already, we are down to about a 50% success rate.
- The ones not showing improvement did not show it to be detrimental or anything.
- So it’s kind of an “it either works or it doesn’t really do anything” area.
Within those positive results, the improvements were also not super consistent.
- One of the most promising studies found that 78% of participants reported that the probiotic improved symptoms. This means that 22% noticed no difference.
- Another study found that 47% of patients in the intervention group reported “adequate symptom relief” whereas only 11% in the placebo group reported that. That’s enough to suggest that it “works” – but it still meant that 53% of people in the intervention group didn’t get large improvements.
- Out of the 14 studies showing improvements in this review, 10 noticeably different probiotics were used.
From a negative perspective, this means it is hard to determine the optimal protocol.
From a positive perspective though, this is a huge area for easy wins in the research going forward.
Protocols in the future will likely be more effective than they are today.
Mental Health
We know that diet and gut health play a role in mental health.
The whole concept of the gut-brain axis makes this clear. And we have evidence of dietary changes leading to improvements in mental health.
A 2017 systematic review on probiotics and depression, anxiety and cognition found 10 relevant studies and identified positive results in all three of those areas.
This is pretty compelling, but a lot of the studies were quite small, and it also fits the same theme of using a variety of different strains.
Immune Function
Probiotics can help immune function through a variety of mechanisms.
An attempt at simplifying how it could help includes:
- Interactions with immune cells
- Improving intestinal barriers through tight junctions in the intestinal wall (aka ‘leaky gut’)
- Suppressing pathogenic bacteria
- Improving T-Cell Activation.
The list of mechanisms is pretty extensive and complex though, so instead I think it makes sense just to look at outcomes e.g. does taking a probiotic mean you get sick less frequently, or for shorter durations or with a decrease in symptom severity?
There are a bunch of studies showing small reductions in the frequency, duration and severity of upper respiratory tract infections.
Some examples in the research that have particularly stood out to me are the cases where the likelihood of catching a cold or flu are higher.
For example, improved outcomes have been shown in children in daycares, or athletes who are intentionally in overtrained states where risk of getting sick is higher due to reduced immunity.
Irritable Bowel Disease
In Crohn’s and Ulcerative Colitis, there are changes in the bacteria in the large intestine. In particular, there are decreases in bifidobacterium and lactobacillus, as well as an increase in pathogenic bacteria.
Intestinal lesions in IBD occur mainly in areas with the highest bacteria concentration. It is proposed that abnormal interaction between the intestinal immune system and pathogenic bacteria triggers the inflammatory response of IBD.
When people are in remission, their levels of the good bacteria are typically higher than when the disease is active too.
You can see based on that mechanism how an approach as simple as supplementing with bifidobacterium or lactobacillus could make sense.
Even though the mechanism makes sense, the outcomes in research so far has not been a little underwhelming.
Quoting a review from 2017 titled “Probiotics in Inflammatory Bowel Disease”
“Available evidence supports the role for probiotics in mild to moderate ulcerative colitis, but not Crohn’s”
I wouldn’t rule out potential benefits in Crohn’s – but I think it is relevant to share that the research so far has not been overly promising.
Summary of Other Conditions
To save time we will briefly summarise the research on the other conditions
- Body composition – Although there are clearly changes in the microbiome between those who are obese and those who are lean, and that has been used to suggest that gut bacteria plays a large role, probiotic supplementation specifically has not shown a major difference.
- On average, there is a small improvement in fat loss in comparison to placebo, but it is less than 1% in terms of body fat percentage, so it is mostly irrelevant.
- Heart health – probiotic have consistent evidence that they can reduce cholesterol and blood pressure a bit. While there is not a lot of direct evidence on cardiovascular disease risk while supplementing probiotics, it would make sense that there might be some benefit.
- Eczema and allergies – the research is mixed at best. It likely does not help.
Overall Summary – Should You Take a Probiotic?
Probiotics can have benefits, but are also a bit hit and miss.
They are worthwhile considering if you have spare money, interest in taking them, and have a condition that could benefit from them potentially. In terms of how to take them, the current simple gold standard approach would be to pick one and take for 12 weeks. If it helps, continue. If it doesn’t, either discontinue or try a different one.
Relevant Links/ Resources
Studies Mentioned:
2016 Review on IBS and Probiotics
Positive Probiotics and IBS Study
2017 Review of Probiotics and Depression
Probiotics Reducing Upper Respiratory Tract Infections in Children at Daycare
Probiotics and Body Composition
Cardiovascular Benefits of Probiotics
Probiotics and Eczema and Allergies
Relevant Blog Posts:
Probiotics for Immunity in Athletes
Prebiotics and Probiotics: What You Need to Know
Are Probiotics Helpful for IBS?
What Is The Best Probiotic For You? Strain Specificity
The Smiles Trial: Nutrition for Depression: Practical Take Away Points