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Probiotics: Proven Solution or Potential Problem?

Q&A with Dr. Jaeyun Sung

Human appreciation for the role microbes play in our health is increasing, and with it, the popularity of probiotics. In 2018, U.S. consumers pulled out their pocketbooks for probiotics, spending $2.4 billion.

According to the National Institute of Health (NIH), probiotics are “live microorganisms that are intended to have health benefits”. While microorganisms as a category include all bacteria, fungi, protists and other small living things, probiotics most often refer to beneficial bacteria and yeasts.

Probiotics come in many forms, from yogurt with live, active cultures to pills that claim to contain billions of the lively little buggers. Recently, more creative probiotic products have been popping up, from probiotic chocolates to skin creams. With claims from improved digestive health to a stronger immune system, it’s no wonder so many varieties are showing up on shelves.

Probiotics do have a lot of potential.

But is supplementing probiotics actually promoting optimal health?

To get answers to this question (and more), we reached out to microbiome researcher Dr. Jae Sung.

Jaeyun Sung, Ph.D.

Assistant Professor of Surgery, College of Medicine, Mayo Clinic

Dr. Sung researches the intricate relationship between commensal microbes and human health. He is especially interested in identifying the biomolecular processes behind microbiome-associated chronic disease. Ultimately, Dr. Sung hopes insights from his data-driven research inspire future investigations into human microbiome complexity and lead to breakthroughs in human health.

Probiotics: Q&A

We’ve all heard plenty of positive things about probiotics. But what do researchers like Dr. Jae Sung say?

Question 1. When are probiotics effective?

It’s not easy to answer when, or under which circumstances, someone should be taking probiotics. Rigorous and systematic clinical studies haven’t shown that any one probiotic supplement can cure a disease, alleviate symptoms, make one healthier (by providing essential nutrients), or prolong lifespan. Let’s set this record straight.

Summary: At this point in time, there is no universally proven probiotic.

However, this doesn’t mean that there isn’t hope. We do know that each of us harbor trillions of gut micro-organisms that maintain our good health. These organisms continuously balance our immune system, aid our digestion, and regulate our hormones. Once researchers identify the bacteria that compose a healthy community (and they’re working on it), a transplant of these microbial communities into our guts may be the best bet.


Summary: There is evidence that microbes aid our immune systems, digestion, and hormone balance. The first step is figuring out what a healthy gut microbiome “looks” like, and from there we’ll learn how to make unhealthy gut microbiomes healthier.

2. According to research, what are probiotics good for, and in what form(s)?

As of now, there are two promising cases that are gaining evidence in the scientific literature. Offering probiotic strains to 1) patients who have taken rounds of antibiotics; and 2) patients who are suffering from a gut pathogen infection, e.g. Clostridium difficile.


Most probiotics are marketed in pill form

Some studies show probiotics can help treat individuals with specific infections, IBS, or antibiotics-sourced diarrhea (meta-analysis here). Microbes like Bacillus coagulans, Saccharomyces boulardii, Lactobacillus rhamnosus GG, Clostridium butyricum, and some probiotic mixtures have evidence behind them.

However, the research is conflicting. While taking probiotics to fill the “hole” that antibiotics blast into the gut microbiome makes logical sense, this may not be the case. A recent study by Suez and others found that individuals who took probiotics following antibiotics actually delayed their gut’s return to “normal”. One catch in the Suez study is that the subjects were healthy volunteers, meaning the only reason for taking the antibiotics was the study itself.

Most often, [probiotics] are taken orally, in pill-form. There have been studies experimenting with rectal insertions.

While taking probiotics in pill-form is definitely one of the more pleasant (and consumer-friendly) ways of bringing good bacteria to your gut, other more extreme methods have shown impressive results. In the same Suez study mentioned above, individuals who took probiotics in the form of a fecal transplant (collected from themselves before the antibiotics) returned their microbiomes to “normal” faster than individuals who took probiotics in pill form or took nothing at all.

Given the conflicting research, a better approach may be to support your existing bacteria buddies with plenty of prebiotic foods following antibiotic treatment.

3. Are there any risks associated with taking a probiotic supplement?

Bacterial culture

There are many, but I’ll propose three:

1. We do not know if these probiotic supplements will actually work as advertised (hence, money down the drain).

2. Clinicians and scientists do not know how the new bacterial will interact with, or perturb, the existing microbial environment.

3. The response after taking a probiotic is very personalized — there are responders and non-responders, and varying degrees within these two groups. Expecting a generalizable response is futile.

These three factors make predicting whether a given probiotic supplement will be beneficial for you virtually impossible (for now). To combat these risks, the future will likely bring highly personalized probiotics.

4. Should the average, healthy person take them?

I don’t see clear evidence that one should. Rather, I’d recommend sticking to wholesome, natural, nutritious foods, which come with their own microbes anyway.

5. Do fermented foods work as probiotics?

Yogurt with live active cultures can act as a probiotic

Many ancient cultures have their own unique fermented foods on their menus. Kimchi, Sauerkraut, Kefir are good examples. Our ancestors probably never knew much about microbes (beneficial or pathogenic). But even so, they likely knew that fermented foods were good for you (if not, why would these foods still be around?). Thus, rather than looking at fermented foods as probiotics, perhaps the correct, and evolutionarily-proven perspective would be to view fermented foods as beneficial foods.

Reverting to foods humans have made and eaten for thousands of years is generally a safe bet. Fermented foods are likely a beneficial addition to any diet, and not only because of their probiotic components. If you’re looking to add fermented foods to your diet, here’s a handy guide to getting started at home.

6. How can you best support your gut microbiome?

Personally, I’d recommend sticking to the right foods. Natural and unprocessed, nutrient-dense, and tested throughout time.

Whole foods have many of the nutrients that your gut microbes need to sustain their own life and keep their community in balance.

While probiotics can be an important treatment option for specific ailments and digestive issues, there’s probably no reason for healthy people to supplement them. This is in part because the relationship we have with the billions of living things in our bodies is extraordinarily complex. According to one estimate, our own bodies contain 1.3x as many bacterial cells as human cells. This ratio is highly individualized, however, and is subject to change after a bout of antibiotics or even a trip to the bathroom.

Until the future brings personalized probiotics, eating plenty of proven foods is probably the best way to go.

Hungry for more microbiome research and reports?

Dr. Jae Sung’s computational work on the microbiome:

How close do you think probiotics are to becoming a proven solution? Let us know in the comments below.