What You Eat and Don’t Eat Can Affect Your Performance, As Well As Your Immune System and Your Susceptibility to Viruses, Such as COVID-19





Hello Runners,

I hope you continue to stay healthy and well in these crazy times. I also hope that you are connecting with other people, including loved ones and friends that you may not have been in touch with for a while. I have appreciated having more time together with my wife, Karen, and our dog, Zadar. I also recently connected with some college friends that I haven’t been in touch with for a while. It was a lot of fun! So, there has been some silver lining to our current situation. I hope you are finding your own silver lining and staying positive.

In a previous blog I provided some tips for building and boosting the immune system. One of the areas of science and medicine that is receiving more and more attention the microbiome and how it can impact health. In this post, I will briefly discuss what the microbiome is, how it can impact your immune system, and what you can do to support your microbiome, so that you can avoid the impact of COVID-19 and other viral and bacterial infections.

What is the Microbiome

The microbiome refers to all organisms that live in and on our bodies, includes bacteria, viruses, fungal organisms, one cell protozoa; basically all microscopic “critters” that inhibit our body. There are more than 100 trillion of these organisms in and on our bodies, which is over three times the number of cells in our body! Most of these microbes are beneficial, however some are not, and can cause disease.

Although all body surfaces, orifices, and cavities are teeming with microbes, the vast majority are located within our large intestine and make up what is known as the gut microbiome or microbiota. Since we can have the greatest effect on microbes in this area of the body, I will focus the rest of this post on the gut microbiome, and not microbiomes of other areas of the body.

The microbes that make up the gut microbiome can have a profound effect on all functions of our body, including hormone levels (can affect performance through such things as energy production), nutrient absorption, metabolism (important for producing the energy we need to run), brain function, and the immune system.

Variety is important for health and performance, when it comes to microbes. Unfortunately, the average American adult has ~1200 different species of bacteria in the gut. This number is significantly less than other populations, such as the Amerindian living in the Amazon of Venezuela which has 1600 species of gut bacteria. This lack of diversity in Americans can be attributed to our overly processed diet, overuse of antibiotics, and sterilized homes. However, the microbiome exhibits plasticity, meaning it can be changed and improved, thus providing us with the opportunity to shape it in a way that optimizes our health, as well as our performance.

How is the Microbiome Connected to the Immune System

As I mentioned, the gut microbiome affects many functions in the body, and it is worth discussing the role it plays in hormone levels, nutrient absorption, and function of the mitochondria because they can all impact our running performance. However, due to our current situation I will focus on the impact that the gut microbiome has on the immune system in this post, and save these other important functions for later posts.

The gut microbes of our microbiome are in constant communication with the part of the immune system (mucosal immune system) located in the intestine. These microbes help the immune system discriminate between harmless foreign entities like food and harmful ones like Salmonella. The microbiome helps train the immune system to make the distinction, so that we have a proper response of the immune system. An improperly trained immune system can lead to allergic reactions to substances that would otherwise be harmless, such as pollen.

Research has shown that the gut microbiome can not only impact the local or mucosal immune system, but also the more systemic immune system, impacting the rest of our body. For example, Hao et al. (2015) concluded from several research studies that consuming probiotics can also lower rates of upper respiratory tract infections, thus suggesting probiotic bacteria can tap into the function of the immune system in the gut (local) and systemically. Probiotics are basically strains of microbes that when taken can temporarily increase the number of microbes in the microbiome. Although there are no current studies showing a positive effect of probiotics on the lower respiratory tract, which is the primary region affected by COVID-19, the fact that microbes in the gut can affect the immune system in the lungs is promising.

In addition, there is some evidence that COVID-19 infection may lead to intestinal infection, as they found the presence of the virus in feces. (Zhang et al. 2020), thus showing the importance of the mucosal immune system in combatting COVID-19, as well as the systemic immune system.

How Can We Support The Microbiome In Order To Support Our Mucosal and Systemic Immune Systems

Basically, we need to provide foods that feed the good microbes and eliminate or at least minimize the foods that feed the bad microbes. This can be a challenge for many runners, who really heavily on foods and beverages with added sugars. These sugars feed yeasts and other microbes that can negatively impact our immune system and health. For events and long runs consider using supplements like UCAN, Vitargo, or Infinit-E (Millenium Sports), instead of the typical gels, sports drinks, etc. that contain significant amounts of added sugars.

It is important to add variety in the diet and not eat the same short list of foods day after day, week after week. This is the opportunity to get a little creative with your recipes and explore some new foods! Eating a wide variety of fiber-containing foods (especially onions, garlic and Jerusalem artichokes, as well as fruits, vegetables, legumes and some unrefined whole grains) provides different fibers to feed a greater variety of microbes, allowing them to flourish. This will also squeezing out harmful microbes, such as Candida. So as far as vegetables, “eat the rainbow”, that is eat vegetables of different colors. As far as fruits, berries are a great option!

You should consume enough fruits and vegetables daily that would include at least 25 grams of fiber per day. The average Americans consumes about half of this. These fiber-containing foods act as prebiotics, because they provide the food for beneficial microbes in the gut, which will promote their growth.

Other foods that can help support the microbiome include coconut oil, omega-3 fatty acids (fish oil or flaxseed oil), and fermented foods (unpasteurized sauerkraut, pickles, kefir, yogurt, miso, kimchi, kombucha). Probiotics, which are discussed below, can also be beneficial.

In addition the intake of other foods should be eliminated or minimized including: processed foods, gluten, dairy, added sugars, alcohol, caffeine, peanuts, beef, pork, and saturated and polyunsaturated fats. These can all be detrimental to the microbiome and gut health and thus, negatively impact the immune system.

What About Probiotics

We hear a lot about probiotics. So, what are they and what is their role in the microbiome and for our immune system health?

Probiotic means “for life” and are “live” micro-organisms which, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO). Probiotic bacteria are transient visitors to the gut and offer a method distinct from diet to tune the microbiome, so that it can more effectively work with the immune system. As they drift through the digestive tract, probiotics communicate with resident microbes and intestinal cells. This can help in fighting colds, flus, and diarrheal illnesses. However, since most probiotics are not well-suited to live in the gut, they are transient and must be consumed regularly.

There are several considerations that should be made in selecting probiotics. First, the probiotics should be refrigerated so that the microbes are live. So, do not purchase probiotics that are not refrigerated because basically you are getting dead microbes that are of little or no value. The probiotics that are available are typically only a few different microbes, basically those that can be most easily produced by supplement companies. The effects of these probiotics can be unique to individuals because of differences in microbiota and this can vary daily as a person’s own microbiota fluctuates. So, it is impossible to predict the effect of consuming a specific probiotic. Thus, it is most beneficial to consume fermented foods in addition to taking probiotics.

Beware of claims by companies pushing probiotics. Avoid buying probiotics from online or e-commerce companies, especially those that sell only one product. Check to make sure third party testing was done in order to insure for safety of the supplement. U.S. Pharmacopeial Convention (USP) provides 3rd party evaluations on product’s labels for supplements. Only purchase supplements from reputable companies.

Discontinue use probiotic products that cause uncomfortable bloating, excessive gas, or headaches.

What’s Your Gut Microbiome Like?

There is still lots to learn about the microbiome and the impact it has on immune system, as well as other aspects of our health, and performance. You can learn about the health of your own microbiome through the American Gut Project. For $99 and a stool sample you can get a list of the bacteria in your gut to see how diverse your microbiome is, as well as how much of your microbiome is beneficial and how much is detrimental to your health. It is also possible to retest your microbiome to see if it has improved with any dietary changes you implement.

Please let me know if you have any questions, or if I can be of help in any way.

Stay healthy and stay positive!

Your friend and coach,




Dr. Robynne Chutkan. The Microbiome Solution.

Dr. Tom O’Bryan. The Autoimmune Fix.

Dr. Mark Hyman, Interconnected Episode 1: The Missing Piece in Health and Longevity.

The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-Term Health by Justin and Erica Sonnenberg, Penguin Press. NYC, 2015.

Yatsunenko, T et al. “Human Gut Microbiome Viewed Across Age and Geography.” Nature, 486.7402 (2012), 222-27.

Zhang Y, Chen C, Zhu S et al. [Isolation of 2019-nCoV from a stool specimen of a laboratory-confirmed case of the coronavirus disease 2019 (COVID-19)]. China CDC Weekly. 2020;2(8):123–4.


Hao, Q, et al. “Probiotics for Preventing Acute Upper Respiratory Tract Infections.” Cochrane Database Syst Rev 2 (2015).

Shi N, Li N, Duan X, Niu H. Interaction between the gut microbiome and mucosal immune system. Mil Med Res. 2017 Apr 27.

Ben Greenfield. Beyond Training.

FAO/WHO Guidelines for the Evaluation of Probiotics in Food. 2002.

Disclaimer: All the information presented in this blog is for educational and resource purposes only.  It is there to help you make informed decisions about health-related fitness issues.  It is not a substitute for any advice given to you by your physician.  Always consult your physician or health care provider before taking supplements or using any other recommendation in this post. Use of the advice and information contained in this website is at sole choice and risk of the reader.  In no way will Denver Running Coach or any persons associated with Denver Running Coach or Enlightened Performance LLC be held responsible for any injuries or problems that may occur due to the use of the advice contained within this post.  Denver Running Coach and Enlightened Performance LLC will not be held responsible for the conduct of any companies recommended within this post.

Disclaimer: Dr. Brian Hand does not invest in or benefit in any way financially from any products mentioned in this post.

Share this: Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedIn

Leave a Reply

Your email address will not be published. Required fields are marked *