Probiotics and Prebiotics: What's the difference?

The digestive tract is home to more than 500 different species of bacteria, comprising about 100 trillion bugs altogether. The human gut contains 10 times more bacteria than all human cells in the entire body. In fact, one could say we are more we are more bacterial than we are human. Together they are tremendously important for overall health. We give these bugs a home and in exchange, they do a variety of things for us. For example:

  • they help digest our food so we can synthesize certain vitamins, such as B vitamins and Vitamin K

  • they play an important role in our immune defense

  • they help regulate metabolism and the breakdown of our hormones

  • they act as a barrier to help our bodies filter and appropriately absorb nutrients from the food we eat.

Many have most likely heard about the “good” bugs called probiotics, which we can constantly replenish (with food or supplementation). But what many do not realize is that these probiotics also need nourishing food to help them thrive and reproduce. The food that helps the probiotics grow are called prebiotics, these prebiotics are rich in fiber, which serves as their fuel source.

In simple terms, probiotics and fermented foods contain the bugs themselves, and prebiotics are the food the bugs need to survive and multiply.

Another benefit of “feeding” these bacteria is the production of butyric acid, propionate, and acetate, which are short chain fatty acids. These beneficial acids are produced when the probiotics break down prebiotic foods in the colon. Butyric acid is the preferred form of fuel for the cells that line the colon, and it serves to acidify the environment as well, making it harder for harmful bacteria to survive. Short chain fatty acids also promote cell differentiation and proliferation, they regulate sodium in water absorption, they enhance the absorption of calcium and other minerals, and they improve gut barrier function and host immunity.

The table below lists examples of common probiotic and prebiotic foods.

In order to maintain colonization in the digestive system, probiotics must be taken or eaten regularly. General recommendations call for ingesting 1 to 25 billion colony-forming units (CFUs) daily. To put this into perspective, most store-bought probiotic yogurts contain about 1 billion CFUs per serving. To get the maximum benefit from fermented foods, it is important to choose food items that say “active, live cultures” and are preferentially raw, unpasteurized, perishable ingredients. Organic brands are best, as they are not typically heat- treated after fermentation, which means that more of the good bacteria will be present. Fermented foods can also be made at home. Home fermenting is a safe way to ensure that you are ingesting beneficial bacteria, as various cultures around the world have done for centuries.

Eat Fermented Fiber!

This should be an easy concept to get our heads around, because everyone says we don’t get enough fiber, and the more fiber the better!!! But this gets tricky quickly. This is due to several reasons, but the main reason is that foods that are high in fermentable fiber can also cause gas, bloating, and stomach pain, especially in people who have irritable bowel symptoms.

When we eat the fibers found in whole plant foods, the bacteria in our gut ferment these fibers (prebiotics). These dietary fibers can be broken down into two main types. Soluble and insoluble fiber. Prebiotics are fiber rich foods that contain soluble fiber. Soluble fiber easily dissolves in water and is broken into a gel like substance in the colon. The gel like substance coats the large intestine, which can be very helpful in cases of constipation and diarrhea as well as other digestive symptoms like gas and bloating. This is different from insoluble fiber, which is a form of fiber that can not be digested by our gut bugs. Insoluble fiber does not dissolve in water and is left intact as food moves through the digestive tract. This kind of fiber can be hard on a person’s GI system if they have an imbalance of microbes (dysbiosis).

I think this is important for people to understand the nuances when it comes to gut bugs, gut health and oftentimes symptoms worsening when eating more fiber. It makes sense to pay attention to this. I hope the chart below helps demonstrate where you can find probiotics and prebiotics. It should be also noted that some find it easier to get prebiotics in a capsule form. This can help increase the amount of fiber in a day as well as reduce symptoms that some have when eating certain foods.

Probiotic FoodsPrebiotic FoodsDairy

*** all fruits, vegetables, nuts, seeds, beans and grains contain some insoluble fiber as well as soluble, but the distribution can be different per food item. For instance raw almonds contain 0.7 grams of soluble fiber and 3.5 grams of insoluble fiber, while flaxseeds contain 2.7 grams of soluble fiber and 2.1 grams of insoluble fiber. Also, every person may or may not tolerate certain foods based on their genes and or digestive makeup.