Written by: Kari Raman, PharmD, RPh
Published March 28, 2023

Prebiotics are non-digestible food components, usually fibers, that act as a food source for the beneficial bacteria and other species in your gut’s microbiome. A great way to get them is by eating what is obviously healthy – various plant-based foods, like whole grains, fruits, vegetables, and legumes. Because your body can’t digest them, they end up making it into the large intestine, where a lot of the healthy probiotic species live. This is where the majority of prebiotics are eaten (that is, digested) by the probiotics in your gut.

I get asked about prebiotics at the pharmacy counter quite a bit. People want to know if they help, if they should take them and how they work. 

How do prebiotics work?

Prebiotics play a key role in promoting a healthy gut microbiome by feeding the healthy bacteria and other probiotics in your gut. When you take probiotic supplements, which contain live beneficial bacteria or other healthy organism(s), prebiotics can help these bacteria to thrive and establish themselves in your gut.

For example, Bifidobacterium is a type of bacteria that is commonly found in the human gut, and has a lot of good probiotic goodness going on, helping with keeping you regular, reducing inflammation, possibly helping with weight management, and more. Bifidobacerium has been shown to be able to digest resistant starches and produce short-chain fatty acids that have beneficial effects on the body.

Prebiotics are a food source for the healthy microbiome that lives in your large intestine and colon. When these healthy fibers and starches reach that part of your digestive tract, the bacteria, yeasts, etc. that are in your gut get to work – digesting and fermenting the prebiotics, and producing helpful stuff that nourishes your colon and intestine cells and body. Additionally, keeping the right bacteria living and thriving in your gut means that bad bacteria and other, less helpful critters, can’t take over as easily and give you gas, diarrhea, and other health problems.

What are the most common prebiotics?

Some common prebiotic fibers include inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS); common probiotic starches are resistant starches and pectin. Read my article on how to take probiotics with fiber here.

How to get prebiotics?

The best way to get prebiotics is through the right foods, although there are some good supplements that can provide prebiotics as well. And there is no surprise about which foods provide the best prebiotics – it’s all that plant-based stuff that you know is healthy. We’ve got a whole article on the best foods for a healthy gut microbiome here. Whole grains, certain fruits, beans, these are all good sources. Here are some of the best ways to get prebiotics from your food:

  • Barley and oats: Both barley and oats contain beta-glucan, a type of prebiotic fiber. They can be used in porridge, baking, or as a base for various dishes. And, of course, oatmeal.
  • Apples: Apples contain pectin, a prebiotic fiber that promotes the growth of beneficial bacteria. You don’t need me telling you how to eat apples.
  • Legumes: Beans, lentils, and chickpeas are rich in prebiotic fibers, such as resistant starch and oligosaccharides. They can be used in soups, stews, salads, or as a protein source in various dishes. Or, if you are like me, just eat a lot of Mexican food.
  • Bananas: Slightly under ripe bananas are a good source of prebiotic fiber called resistant starch. They can be eaten on their own or added to smoothies, oatmeal, or yogurt. The problem is that the less ripe the banana the more prebiotics it has – but unripe bananas really aren’t that great.
  • Garlic: Garlic contains fructooligosaccharides (FOS) and has prebiotic properties.
  • Onions: Similar to garlic, onions also contain FOS and have prebiotic effects. They can be consumed raw, cooked, or caramelized and used in various recipes.
  • Leeks: Leeks are part of the same family as onions and garlic, and they also contain FOS. Take a leek!

And prebiotics aren’t the only great thing you can get for your gut by eating healthy, “whole” foods. Another great thing that research is showing is good for your microbiome are fermented foods. I’ve written a whole article explaining the latest research on how fermented foods alter your microbiome – check it out. The newest research is pretty exciting – it’s not that you are what you eat, but in terms of what’s in your microbiome, it does turn out that what you eat can actually become a big part of the healthy microbes in your gut!

Synbiotics – combining prebiotics with probiotics

Combining prebiotics and probiotics is often referred to as “synbiotics.” In latin, ‘syn’ means to combine or along with – so synbiotics means combining pre and probiotics. If you are taking probiotics, or even just want a healthy gut, there needs to be a lot of food for the bacteria, yeasts, etc. in your gut to eat. A synbiotic approach can improve the effectiveness of probiotics by:

  • Providing a nutrient source: Prebiotics serve as fuel for probiotics, allowing them to grow, multiply, and function optimally within the gut.
  • Enhancing colonization: Prebiotics can help probiotics better adhere to the intestinal lining, increasing the likelihood that they will establish themselves in the gut and exert their health benefits.
  • Modulating the gut environment: Prebiotics can alter the gut environment in ways that are conducive to the survival and function of probiotics, such as lowering pH levels, which can inhibit the growth of harmful bacteria.
  • Stimulating immune function: Both prebiotics and probiotics can have positive effects on the immune system. By working together, they may enhance these effects and promote overall health.
  • To optimize the benefits of taking probiotic supplements, it is essential to maintain a diet rich in prebiotic fibers. Consuming a variety of fruits, vegetables, whole grains, and legumes can help support the growth and activity of the beneficial bacteria introduced by the probiotic supplements.

If you want a healthy gut, it’s important to eat a well rounded diet with lots of good fibers and other prebiotics. And if you are going to take a probiotic supplement, it makes sense to not only step up your fiber intake through good foods, but to also consider a prebiotic supplement.

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Pharmacist Kari Raman

I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

Probiotics are confusing!

One of the most common questions I get asked by patients is about probiotics. And the truth is, probiotics are not as well understood by the healthcare community as they should be.

So I’ve been reading a lot of probiotic clinical trials, and sharing what I’m learning here.

I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!