Foods to Fuel Your Gut Microbiome


Sharon Sun


July 19, 2022

Would you believe that what you eat is associated with feeling low mood or happiness, stress or relaxation, illness or wellness? As discussed in the previous part of this series, our gut is essentially our ‘second brain’. However, I would even argue that our gut is the ‘first brain’ at the forefront of health and wellness. What happens within can trigger a host of responses from impacting our immune system to our mood or even our risk for certain disease conditions! Understanding the gut-brain connection is a starting point towards optimal health and you can find out the basics about it here!

The Gut Brain Connection (Snack Version)

In case you want the snack version, here is a summary of what was covered:

  • The gut-brain axis is connected via a ‘highway’ called the vagus nerve. Your gut microbiota can stimulate the vagus nerve to positively affect mood and may even be a line of treatment for mood disorders (2,3)
  • Some real-life interpretations of the gut-brain axis include the use “gut-feeling” term, “butterflies in the stomach”, and the urge to go to the bathroom when nervous (1)
  • Some neurotransmitters are even made in the gut (hello, serotonin!)
  • A leaky gut is when there is an imbalance of gut bacteria which leads to a weakened gut membrane, causing inflammation (aka a very sad gut)
  • We can contribute to a healthy gut by including nourishing foods (which takes us to this post!)

The big question: What foods can I eat to help me create a healthy gut?

Luckily there is no better time to start including more nutritious foods than by the end of reading this sentence. In fact, our gut microbiome adapts rather quickly to major shifts in the diet and can change/respond in just a few days (15)! That means the more gut-supportive foods we offer to our bodies, the quicker we may also experience positive corresponding changes to our mental and physical wellbeing. Here are some foods to kickstart that friendly gut:

Reminder: In the age of conflicting nutrition information and unwarranted food scares, differentiating food facts from fiction starts to become a game of finding the needle in the haystack. At the end of the day, our overall eating habits will provide the big picture of our health as opposed to what we choose to have (or not have) at a single meal. It is way (way, way, way) more paramount to include a variety of foods with the goal of nourishment in mind. Remember, nourishment not only comes as physical nourishment to our bodies but also mental nourishment when we truly enjoy the foods we eat. So yes, have the rainbow of veggies but also sprinkle in that ice cream too.

Food Bestie #1: The Probiotics Squad

You may have heard about these superstars and for good reasons too. These live microorganisms provide a plethora of benefits to our guts. Although they do not take over the gut, they can interact with other resident microbes just by passing by and influence our immune system like resident microbes would (5)! Two of the most well-studied probiotics, Lactobacillus and Bifidobacterium, are some of the most impactful of the bunch, linking their consistent consumption with benefits such as improvements to mood, depression, and anxiety (6 ,7, 8) among others.

Probiotics: Food for thought (quite literally) – How do they work?

Do you recall that some important neurotransmitters are made in the gut? Well, probiotics have a role there, helping to make the neurotransmitters that affect our feelings, mood and cognition (serotonin, GABA, dopamine)! It is thought that they protect our gut by sticking to our intestinal cells and covering specific receptor sites (protein sites that receive signals). This makes it difficult for pathogenic bacteria (the bad guys) to attach to them or affect them (9). To top it off, probiotics are also quite notorious for stimulating the production of lactic acid and special compounds called short-chain fatty acids (SCFAs). Both of these compounds help to lower the pH in our guts, making the environment more acidic and non-favourable to pathogens. Quite figurately, probiotics are our knights in shining armor when in comes to protecting our guts in a battlefield of pathogens!

Your probiotic army: Try these delicious probiotic-containing foods and recipes!
Note: While consuming probiotics does offer a host of benefits to the gut, make sure to think about your diet as a whole! I may sound like a broken record by now (if not now, then later), but cannot stress enough the significance of eating a variety of foods, particularly fiber-rich ones that would also best support a healthy gut microbiome (more in the next section!). In contrast, it is quite possible to reduce the benefits of probiotics if the diet in context is also one that is significant in added sugars and processed foods. Essentially, these would be the storm that wipes the nation of gut-friendly probiotics and their hard work and that’s something we would not want!

Food Bestie #2: Resistant Starches and Prebiotic Foods

We eat food to get our daily doses of energy but does that mean our gut bacteria need ‘food’ too to do their work? This is where resistant starches and prebiotics come in! Simply described, resistant starches are a type of starch which – you got it – resists digestion in our small intestine. That means they do not get absorbed in our body but end up making their way to our large intestines instead. If this sounds familiar, you are probably thinking about fibre and resistant starches are essentially that; a type of low-viscous fiber! As they have the properties of fibre, they are available to bacteria in our guts which use them as a source of food (prebiotics). These are then fermented by the gut bacteria which also produce SCFAs as mentioned previously. SCFAs help promote a healthy home for the good gut bacteria to live and grow in while also providing energy to our colon cells (via butyric acid) or providing indirect source of energy for our livers to use (via propionic acid). In essence, when we have a balanced diet, we feed both ourselves and our gut bacteria so that they can do the work of, well, making more energy and keeping our gut homes clean of harmful bacteria. It’s really a win-win situation.

Where can I get some prebiotic goodness?

Unlike the sporadic periods of snow received here in BC in December, there is absolutely no shortage of sources of prebiotics at the grocery store. Every food that you could possibly imagine to have some fibre in it will also likely have prebiotic fibers: vegetables, fruits, whole grains, legumes, nuts and all the good stuff one may shy away from. The following is handy list of types of dietary fibres that have prebiotic function because science loves classifications and also brewing up confusion:

  • Resistant starches
  • Fructans (ie. inulin)
  • Beta Glucans
  • Pectin
  • Oligosaccharides: Galacto-oligosaccharides, Fructo-oligosaccharides
Are you getting enough fibre?

Most individuals are only getting about 40-60% of their recommended amounts of fibre (38g for adult men, and 25g for adult women). Here’s a list of high fibre, high prebiotic foods and some easy recipes to help you get started!

*Fun food facts: How you prepare foods can affect the levels of starch and resistant starch in them! When potatoes are cooked and then cooled, the cooling process turns some of the digestive starches into resistant starches (a process called retrogradation). The resistant starches are the ones that act as fiber and can provide the gut benefits mentioned above as well as helping to stabilize blood sugars (find out more about the Glycemic Index of foods).

Food Bestie #3: Polyphenols (Berries, cereals, nuts, beverages)

If the name itself is not enough to make you believe that polyphenols are some sort of magic potion, think again. They’re quite known for their ability to fight against cancer-causing agents, reduce diabetes risk, act as an antioxidant, and have brain-protecting properties (10). What’s more is that they are quite abundant in food, from fresh summer berries to your favourite morning matcha latte (oh, that’s my favourite), there’s really no way you could avoid them.

Here is some convincing evidence for polyphenol supporting gut health:
  • Improve gut fermentation: When polyphenols are in our diet along with fibers, together they can increase the rate of fermentation in our gut (12). Just by adding some berries, for example, we can enhance the benefits we already receive from fermentation and change how much SCFAs our gut microbiota makes (13). But also, isn’t it amazing how many things work together synergistically?
  • Polyphenols may have prebiotic-like properties even in the smallest amounts (10)
  • They help with good and bad bacteria: After polyphenols from cereal grains are broken down (into their metabolites), these can increase the amount of the good bacteria Lactobacillus and Bifidobacteria (10) Not only that, but their antimicrobial properties also fights against the bad. For example, high amounts of flavanols (a type of polyphenol) in dark chocolates can supress the harmful toxins caused by E. coli and improve their otherwise long-term health consequences (14) If you needed a reason to go for that that piece of chocolate, there you have it!
  • They protect the gut: Overall, they control the immune response of the gut and reduce any metabolic problems (11) while protecting the gut from any oxidative damage.
The ultimate polyphenol food bucket list:
  • Berries: Especially raspberries, blackberries. Blueberries and strawberries have less but are still great options. Think blues and reds that would be fantastic in a Berry Protein Smoothie Bowl.
  • Vegetables: Onions, Artichokes
  • Green tea
  • Red wine (double yes!)
Are polyphenols for everyone?

While I could never deny you of having a bowl of raspberries offering a host of benefits alongside polyphenols, there are some things to keep in mind. Just as your gut microbiota is not the same as mine, or your neighbour’s or your dog’s, experiencing the benefits of these polyphenols will be different for everyone. A different microbiome will affect how the polyphenols in your diet are transformed and/or metabolized (10). Depending on the phenolic compounds (the products of metabolizing polyphenols) available, their interactions and thus health outcomes in guts and will vary between people. Nevertheless, the evidence of polyphenols on general benefits such as stopping the growth of bad bacteria in the gut is well supported and this can’t be underestimated!

A final recipe for a healthy gut

Reminder #1: While I enjoy talking about food (all day), remember that diet and nutrition is only one area of health. A healthy diet must be considered alongside other factors such as stress, low water intake, sedentary lifestyle and lack of sleep. All of these also affects how our gut microbiome and their ability to do their work! Make sure you are thriving in all of these areas and if you need a little help doing so, reach out to a health professional!

Reminder #2: Many health-related goals may appear to take light-years away to reach but the benefit of making a dietary change now can make notable changes to your gut microbiome in little as 24 hours (4)! I can/will also assure you that keeping up the goal of long-term nourishment will also reap the benefits a thousand times in the future and something your past self will thank you for so start today!


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