What’s up with probiotics?

You heard about the rising trend of gut health research, fecal transplants, probiotics, and prebiotics. The real question is- do they work and should you take them regularly?

What is the difference between probiotics and prebiotics?

Probiotics are good bacteria found in all sorts of food and supplements. Our bowel is comprised of a multitude of types of bacteria, some of which are good for gut health and some of which are bad. Prebiotics are an umbrella term that refers to all sorts of minerals and compounds our gut bacteria like. The key is that these supplements are beneficial for both good and bad gut bacteria.

There is a ton of research about the effects of taking probiotics and prebiotics and how they affect our gut microbiome.

There are also a lot of opposing opinions regarding probiotic use- some swear by it, while others think it’s just a pharmaceutical ploy to make some extra profit. That extra profit is around 80 billion dollars globally. 

So the next question is what to think of it. How to form an unbiased opinion about these supplements, since even experts disagree on a lot of matters about probiotics?

Health benefits of probiotics

Your gut contains trillions of bacteria of all kinds that feed on the food you eat. Some of these bacteria have a symbiotic relationship with us, meaning both our body and the bacteria benefit from this weird relationship. We offer them food, aka a source of energy, and they keep our GI motility in check, but also help us digest food, produce some vitamins, and so on. Other bacteria are bad bacteria that have a parasitic relationship with us, meaning they have benefits that we provide them as their energy source, but we have no benefits at all, or they can even be harmful to us. The third type of bacteria that reside in our gut simply live there, and we have no benefit from them being there.

The term good bacteria may be a wrong term since they can be called good only when there is a normal concentration of them and when they reside only in our gut.

An example of this is E. coli, which is one of the most popular gut bacteria. It is an excellent producer of vitamin K when it resides in our gut, but it can cause urinary tract infection once it reaches your urinary tract or your bladder. Another way E.coli can be toxic to us is when we wipe out other good bacteria and leave E.coli to have a monopoly over our gut microbiome. This "wiping" of your gut biome is most often caused by the use of antibiotics. Antibiotics are one of the most important tools in modern medicine, but they are not without their problems. Since antibiotics (especially extended-spectrum antibiotics) don’t recognize good from the bad bacteria, they can basically wipe out most of our microbiome, whether it’s good or bad bacteria.

An example of this would be the overprescription of the antibiotic clindamycin, which basically clears your infection (pneumonia, for example) but also the gut microbiome, leaving us with a bad gut bacterium called C.difficile.

Sometimes doctors will recommend probiotics when prescribing antibiotics, but unfortunately, this is more often than not pretty useless.

Some studies suggest that taking probiotics and prebiotics leads to faster restoration of your normal gut microbiome, while others suggest that inappropriate use of these substances can even prolong your GI symptoms and worsen the already messed-up gut flora. However, like most things in medicine, there is a catch. While a normal microbiome is strongly linked to improved gut health, mental health, focus, and immune system response, taking over-the-counter probiotics might not be the best idea since we actually don’t know what type of bacteria reside in your colon.

Both genetic and environmental factors, such as stress and diet, significantly affect your microbiome, and once it’s wiped out by antibiotics, we don’t know what bacteria are missing. If you buy over-the-counter probiotics, they usually contain all sorts of bacteria, and there is a chance you never even had those types to begin with. So sometimes the best-case scenario is that probiotics do nothing for you, and the worst case is that you create a further imbalance in your gut flora.

Another caveat that I would like to add is that there is a possibility for you to add too much bacteria that you already have in your gut, and also create an imbalance. This scenario is less likely to occur since our gut is really good at regulating these ratios of good vs. potentially harmful bacteria.

The second brain

If you read anything about the gut-brain axis or the health of your microbiome, you probably heard that your gut is sometimes called your “second brain” since it contains a lot of nerve cells, and you probably heard how most of our neurotransmitter serotonin is produced in our gut.

While that is true, you have to know that just because serotonin is called the “happy hormone”, it doesn’t mean that a lot of serotonin will lead to feeling happier or emotionally better. The reason for that is the fact that all of our neurotransmitters have to act on certain neuronal pathways to ensure proper activation or deactivation in our brain.

Loss of dopamine neurons in Parkinson’s disease, for example, doesn’t make patients more depressed since the pathway on which this dopamine acts is mainly the motor pathway, which regulates fine motor control, leading to symptoms like tremor, rigidity, bradykinesia, and so on.

Another thing you need to take into consideration is the fact that most of the serotonin produced in the gut acts on pathways in the gut itself, and not on “happy” pathways in our brain. Because of this, some SSRI antidepressants like Zoloft can cause GI symptoms like diarrhea, loss of appetite, and bloating at the start of your therapy regimen. This is because Zoloft acts by inhibiting the reuptake of serotonin, leading to more serotonin available in your gut, which affects your GI motility, leading to these side effects.

From an evolutionary perspective, our gut being our second brain makes complete sense since the goal of our species is to eat in order to survive, so our gut needs to have all the neural networks to allow it to function properly.  More studies need to be done to understand the gut-brain axis, but there are already some promising research papers about this topic.

So what can we do?

Even though there is a lot of disagreement on probiotics and prebiotics, there is a procedure that most doctors and scientists nowadays agree is effective. It’s called a fecal transplant.

The basic premise is that doctors analyse your gut microbiome by collecting your stool sample, and they insert a piece of your stool back into your colon once the antibiotic course is finished. That way, doctors are certain what kind of bacteria reside in your gastrointestinal tract and can replenish it once antibiotics finish their work.

Some studies suggest that people who underwent fecal transplant procedures have much fewer GI symptoms in comparison to those who took over-the-counter probiotics.

Of course, it is much more convenient to take a pill than to have your fecal matter sampled from you, but there is some promising epidemiological research that looks into specific genes and diet regimes of different populations in order to produce specific probiotics and recommend specific prebiotics for a specific group of people with specific diseases and conditions.

As you can see, the word specific is quite important here.

The story about gut health is a complex one without an easy way out. More research is needed to pinpoint the exact conditions in which these supplements might be helpful.

So next time your doctor recommends over-the-counter probiotics, take their advice with a grain of salt.

Summary: 

Probiotics vs. Prebiotics:

• Probiotics are beneficial bacteria found in foods/supplements.
• Prebiotics are compounds that feed both good and bad gut bacteria.

The Gut Microbiome:

• The gut contains trillions of bacteria: beneficial (symbiotic), harmful (parasitic), and neutral.
• A balanced gut microbiome supports digestion, vitamin production, immunity, and potentially mental health.

Concerns with Probiotics:

• Over-the-counter probiotics may not be effective since they often don’t match the individual’s unique gut bacteria.
• Inappropriate use can disrupt gut balance or be ineffective, especially after antibiotics.
• Some doctors recommend probiotics with antibiotics, but the benefit is debatable.

Gut-Brain Axis:

• The gut, rich in nerve cells, produces neurotransmitters like serotonin, but most act locally in the gut, not the brain.
• This explains why some antidepressants affect GI function.

Fecal Transplants:

• Seen as a more targeted and effective method to restore gut health after antibiotics.
• Reintroduces a patient’s own microbiome rather than generic bacteria.

Takeaway:

• The gut microbiome is complex and personalized.
• There’s no one-size-fits-all probiotic.
• Fecal transplants show promise, but more research is needed.
• Be cautious with probiotic supplements—their benefits are still under investigation.