Nutrition

Prebiotics and Probiotics: What Every Trainer Should Know

As a personal trainer, your primary goal is to help clients improve their fitness. But it’s common to help clients in other ways too. Sometimes this involves giving advice about foods they need to eat more of, like lean meat or veggies. Other times it involves talking about which ones they should cut out, such as cookies and cake. 

One question you may get more often over the next few years is whether they should take prebiotics or probiotics. Especially since the market is expected to grow by 9.8 percent over by the year 2024. How should you respond? Providing the best answer possible requires that you first understand what each one is.

Prebiotics and Probiotics Defined

Research shares that there is no universal definition for prebiotics. This can make them harder to understand enough to recommend their use. It also makes them more difficult to explain to clients.

In simple terms, prebiotics are plant fibers that are not digestible by the human body. As such, they are normally found in fiber-rich foods like fruits and vegetables. They also cannot be absorbed by the gastrointestinal tract. 

An article published in the journal Foods further explains how prebiotics impact our gut microbiota. If this term is new to you, gut microbiota refers to all the microorganisms in our digestive tract. It is in this tract that prebiotics are reduced to short-chain fatty acids. Once this fatty acid enters the bloodstream, it provides many health benefits. 

How are these different than probiotics? 

For starters, probiotics are live microorganisms. And though they also help improve gut health, they are not necessarily found in fibrous foods. Instead, they are in fermented foods such as yogurt and pickles. 

The Mayo Clinic adds that prebiotics “act like fertilizer,” or food for probiotics. They work by promoting the growth of good bacteria in the small intestine. This is different than probiotics which directly increase the healthy bacteria in your gut.

Normally, when we hear the word “bacteria,” we think of it as something bad. For instance, if we get cut, we are told to instantly rinse the cut to get rid of any bacteria it may contain. Then we are told to cover it with a bandage, preventing additional bacteria from getting in. The thing is, not all bacteria are bad. Especially when it comes to the bacteria that live in our digestive tract.

The Connection Between Good Bacteria and a Healthy Gut Microbiome

According to Harvard Medical School, our digestive system has around 1,000 species of bacteria. Some are good bacteria and others are bad bacteria and, together, they equate to roughly 100 trillion total bacteria. 

These bacteria work together to create a healthy gut microbiota which can support many functions. One is breaking down the nutrients in our foods so our bodies can use them. It also protects us against infection. A healthy gut even helps our body create the nutrients we need for optimal health. One that falls into this category is vitamin K which is used to help our blood clot.

Harvard further states that there is a connection between gut health and health in general. For instance, when you have a healthy gut that is loaded with good gut bacteria, you will likely have:

  • Fewer rheumatoid arthritis symptoms;
  • More protection against certain types of cancer;
  • A lower risk of heart disease; and
  • An immune system that could help attack tumor cells.

Research Reveals Beneficial Effects of Pre and Probiotics

Some studies have looked specifically at prebiotic fiber or probiotic bacteria and how they affect our health. What did they find?

One study shares that two bacteria that can help improve gut health: Bifidobacterium and Lactobacillus. Common prebiotics (such as inulin and other oligosaccharides) increase the production of both. 

This study also reports that the prebiotics inulin and oligofructose help the body better absorb certain nutrients. Calcium is one. So, in this way, prebiotics aid in the growth of strong teeth and bones.

The Cleveland Clinic adds that pre and probiotics can be helpful for those suffering from specific diseases. Inflammatory bowel syndrome, urinary tract infections, yeast infections, and gum disease are a few to consider. 

Recommending Food-Based Prebiotics and Probiotics

The good thing about pre and probiotics is that they are found in a variety of foods. This makes it easy for clients to add them to their diet by following a meal plan that includes a few of these items.

Prebiotic food sources that are high in dietary fiber include:

  • Chicory root
  • Dandelion greens
  • Jerusalem artichoke
  • Garlic
  • Onion and leeks
  • Asparagus
  • Bananas and apples
  • Barley and oats

Probiotic foods include fermented sources such as:

  • Yogurt
  • Kefir
  • Sauerkraut
  • Tempeh
  • Kimchi
  • Miso
  • Kombucha
  • Pickles

When creating a diet that supports gut health, include foods such as these. Talk about their benefits and provide recipes that use these ingredients. Help your clients make them a regular part of their diet.

Foods That May Work Against a Healthy Digestive Tract

There are also a few foods and ingredients that can work against a healthy microbiome. One of the most notable is sugar because it promotes the growth of “bad bacteria.” This is important because bad bacteria has been linked to higher levels of body fat. That is in addition to all of the other negative effects of sugar, such as a higher risk of death. 

Another dietary item to avoid is alcohol. Research has found that drinking too much can alter the gut microbiota. So, limiting or avoiding this category of beverages can help improve digestive health.

These recommendations are in addition to eating primarily whole foods. This will help clients avoid the many health-related dangers associated with processed foods. This includes a higher risk of obesity, which raises risks of other diseases as well.

Tips for Using Prebiotic and Probiotic Supplements Safely

Although eating foods rich in pre and probiotics can help clients improve their gut microbiota, some want to take supplements instead. If this is what your client wants, the Mayo Clinic stresses that they should consult their doctor first to ensure that they are safe.

Medical News Today adds that some people should not take these types of supplements at all. Among them are:

  • People diagnosed with Crohn’s disease
  • People with weak immune systems
  • People with underlying medical conditions


If you want to offer clients guidance about more than probiotics or prebiotics, becoming a nutrition specialist is an option to consider. The ISSA offers a Sports Nutrition Certification program. In it, you will learn how certain foods can impact a person physically and mentally. You’ll also gain the knowledge necessary to create customized eating plans. This will help clients meet their health and fitness goals. Check out this certification today!

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Sports Nutritionist

ISSA’s Specialist in Sports Nutrition (SSN) program prepares personal trainers to expand their practices into the specialized area of sports nutrition. Trainers learn how to optimize client performance by combining well-designed training programs with performance nutrition.

Please note: The information provided in this course is for general educational purposes only. The material is not a substitute for consultation with a healthcare provider regarding particular medical conditions and needs. Be sure to check the statutes in your state regarding the nutrition information that non-licensed individuals are able to dispense.

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