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Why "Good" Gut Microbes

(And The Prebiotics and Probiotics That Help Them Flourish)

Are So Good For Your Skin

Probiotics and Eczema

Probiotics and Eczema

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Key points

  • A healthy gut is very important for overall health, and a healthy gut needs to contain good microbes. Your gut already contains some of these good microbes, and you can help them flourish by eating the right foods. The right foods include many foods that are naturally rich in fiber. These foods are called prebiotics.

  • You can also consume good microbes in the form of probiotic foods or supplements.

  • These good microbes that live in your gut promote good skin health in several ways. 

Why do people keep talking about apple cider vinegar? Why do so many young people drink fermented tea (kombucha)?


One reason is probiotics. 


It seems as though we're hearing a lot more about probiotics these days. In the refrigerated aisle, I've seen multiple products--yogurt, juice, miso, sauerkraut, kimchi--that loudly announce that they contain probiotics. Products I'd never heard about before-like kefir, a fermented milk beverage, and kombucha, a fermented tea beverage-suddenly seem to be very popular. 


One of the reasons they're increasing in popularity is due to research. Multiple research studies have now demonstrated that some probiotics have health benefits. They even appear to promote skin health.  

  • Question 1: Why should you make sure that your gut contains "good" microbes? 
  • Question 2: What are probiotics?  
  • Question 3: How do probiotics (and the good microbes that live in our gut) act to help the skin?

There are a lot of probiotic foods available in grocery stores now, from pickled vegetables such as carrots and cabbage, to fermented dairy products, such as yogurt and kefir.

Question 1: Why should you make sure that your gut contains "good" microbes? And how can you make sure that it does? 



  • Your GI tract, also known as your gut, is very important for your overall health. A healthy gut contains trillions of bacteria and other microbes. These tiny organisms live within us, and help keep us healthy.

  • You can think of your gut as a garden. You should be growing flowers (the good bacteria) and keeping away the weeds (the pathogens).One of the best ways to grow more flowers is by adding fertilizer. And one of the best fertilizers for your gut is prebiotic foods. To grow more good bacteria in your gut, you should be eating more prebiotics, especially fiber-rich vegetables. 

  • You can also consume good bacteria, in the form of probiotic foods or supplements.

Much research has now demonstrated the importance of maintaining a healthy gut. A healthy gut depends on the microbes that live in our gut (including bacteria, fungus, and other organisms). These microbes play an important role in our overall health, because they help digest food, extract nutrients, and even help train the immune system.


One of the most important factor in maintaining a healthy gut is providing the right type of food. Prebiotics are defined as foods or substances that promote the growth of good microbes. [Gibson] One of the most common type of prebiotic food category is foods rich in plant fibers. Especially vegetables. [Holscher

I think of it this way: you can eat prebiotic foods, and that helps you grow your own probiotics (right there in your own GI tract.)

While you can ingest foods or supplements that contain good microbes (known as probiotics), that by itself won't ensure a healthy gut. Those good microbes need the right type of food to grow and thrive. And that means prebiotic foods, especially fiber-rich fruits and vegetables. 


Question 2: What are probiotics?

(Can you actually eat "good" microbes to help maintain a healthy gut microbiome?)


If it's so important that your gut contain good microbes, can you eat these good microbes?


Yes, you can, in the form of probiotic foods and supplements.


Probiotics are defined as live microorganisms (such as bacteria) which, when consumed in adequate amounts (via foods or supplements), provide a health benefit. These health benefits include effects on our overall health, our gut, and our skin.  

You may have heard probiotics referred to as "good bacteria". When you buy a carton of yogurt that advertises the presence of "live, active cultures", you're buying probiotics. 

Yogurt containing "live, active cultures" is one type of probiotic food

Probiotic foods have been prized in many cultures for centuries. I met a colleague from Czechoslovakia who told me how her grandparents were adamant about eating a daily dose of sauerkraut every day in the winter. Friends from India tell me that when they were growing up, they were told to eat their yogurt every single day because it was good for them.


Research has now found that probiotics are indeed important for our health, and studies have started to unravel why that is.

Dermatology researchers in particular have become very interested in probiotic foods and probiotic supplements. That's because a number of clinical trials have suggested that they may help in the treatment of inflammatory skin diseases. The most evidence comes from studies of patients with atopic dermatitis (also known as eczema).


In one summary study, researchers combined the results of multiple trials to see if there was any benefit to using probiotics as a part of eczema treatments. In this study, researchers looked specifically at synbiotics. [Chang] 


Synbiotics are a combination of probiotics and prebiotics.  In this summary study, researchers found that synbiotics were helpful in the treatment of atopic dermatitis in adults and children (over the age of 1 year), when used for at least 8 weeks, and when the probiotics combined multiple strains of bacteria.  

Foods that contain "live, active cultures", such as fermented cabbage, are considered probiotic foods

Probiotics may come in the form of foods or supplements.  For foods, this includes a wide variety of fermented foods in which "live, active cultures" of microbial communities are a key component. This includes fermented dairy products (such as yogurt and kefir), fermented cabbage (such as sauerkraut and kimchi) and others (such as miso, tempeh, vinegar, other pickled vegetables, and other foods). 

There are a number of commercially available food products also, in which live microbes are added to food products, such as juices and snack bars. There haven't been enough studies on these to know how effective they are, but studies have suggested that they contain a much lower number and diversity of microbes. [Scourboutakos] 


In terms of probiotic supplements, there's been a lot of research but no definitive answer as to which are best. In the summary study looking at atopic dermatitis, the individual studies used a number of different probiotic supplements. These vary quite a bit in terms of variety and type of microbes, as well as a huge variation in dosage of microbes. 


There are still many unanswered questions about probiotic foods and supplements.


  • Can the ingested microbes survive in our gut? For some microbes, research indicates that they can survive, at least temporarily.

  • How can you help these microbes survive in the gut? As discussed in Question 1, those good microbes will only thrive if you feed them the right food, meaning more fiber-rich prebiotic foods. 

  • What is the best type and dose of probiotics? These are areas in which we definitely need more research. We don't yet know the optimal dose and type of probiotic supplement. However, I can definitely recommend eating more probiotic foods.

Question 3: How do probiotics (and the good microbes that live in our gut) act to help the skin?
Key points:
  • Act to counter "bad" bacteria
  • Have anti-inflammatory effects
  • Produce metabolites that combat free radicals
  • Help protect the lining of the gut

Research has suggested several ways in which good microbes may help the skin. This includes microbes that we consume (probiotics) as well as the good microbes that already live in our gut.  To make it easier to follow, I refer to both types of microbes below as "probiotics".



1. First, probiotics help to counter the "bad" bacteria in our guts. [also known as "pathogenic" bacteria] These pathogenic bacteria have been linked to several chronic diseases.



2. Probiotics also are likely to help because they have anti-inflammatory effects. In a study in mice, taking an oral probiotic bacteria helped to calm down T-cell mediated skin inflammation. [Hacini-Rachinel]  



3. Probiotic bacteria also produce certain substances, called metabolites, that have effects of their own. These metabolites include short chain fatty acids. In a laboratory study, these metabolites were able to combat the formation of reactive oxygen species. (ROS) [Jensen]  I've talked about ROS before, because they're a type of free radical, and free radicals have been linked to skin damage.



4. Finally, we know that probiotics help protect the lining of our gut, known as the intestinal epithelium. They've also been shown to help our skin barrier. In one trial, the use of an oral probiotic in human subjects helped improve the function of the skin barrier, and helped reduce skin sensitivity. [Gueniche] 

Why probiotics are good for the skin Ins



Because of these key features of probiotics, I've included them in my dietary recommendations for healthy skin. One of my main recommendations for healthy skin is to "eat power", meaning focus on eating foods that provide powerful nutrients. That includes a dose of probiotic foods, and it includes a healthy dose of plant fibers (prebiotic foods) to help those good microbes grow and thrive. 



Chang YS, Trivedi MK, Jha A, Lin YF, Dimaano L, Garcia-Romero MT. Synbiotics for prevention and treatment of atopic dermatitis: a meta-analysis of randomized clinical trials. JAMA Pediatr. 2016;170(3):236–42


Gibson GR, Scott KP, Rastall RA, Tuohy KM, Hotchkiss A, Dubert-Ferrandon A, Gareau M, Murphy EF, Saulnier D, Loh G. Dietary prebiotics: current status and new definition. Food Sci Technol Bull Funct Foods 2010; 7:1-19

Gueniche A., Phillippe D., Bastien P., Reuteler G., Blum S., Castiel-Higounenc I. Randomised double-blind placebo-controlled study of the effect of Lactobacillus paracasei NCC 2461 on skin reactivity. Benef Microbes. 2014;5:137–145.


Hacini-Rachinel, F., Gheit, H., Le Luduec, J. B., Dif, F., Nancey, S., & Kaiserlian, D. (2009). Oral probiotic control skin inflammation by acting on both effector and regulatory T cells. PLoS ONE, 4(3). 


Holscher HD.  Dietary fiber and prebiotics and the gastrointestinal microbiota  Gut Microbes. 2017; 8(2): 172–184

Jensen G., Benson K., Carter S., Endres J. Ganeden BC30 cell wall and metabolites: anti-inflammatory and immune modulating effects in vitro. BMC Immunol. 2010;11:15


Scourboutakos MJ, Franco-Arellano B, Murphy SA, Norsen S, Comelli EM, L’Abbe MR. Mismatch between Probiotic Benefits in Trials versus Food Products. Nutrients 2017 Apr; 9(4): 400.

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