Prebiotics & Probiotics: What they are, and where to find them

By: Lauren M. Koch, RDN

Who knew that bacteria, of all things, might just be the key to good health? Scientists, that’s who. They’ve been busy at work, linking the human microbiome to all sorts of important functions in the body. Things like a stronger immune system, balanced mood, and even how we regulate weight.

Turns out, we should be more focused on nurturing our resident bacteria, than eliminating it. Here’s how.

Before I go any further, I think it’s important to define a few terms. Sometimes we medical folk throw lingo around all loosey goosey (I’ve been dying to use that phrase! Thanks for indulging me). Right, back on track. Definitions.

  • Microbiome. The unique colonies of microorganisms that live in and on our bodies, including any genetic material they contain. Each of us has somewhere between 10-100 trillion bacteria taking up residence. In somewhat more graphic terms, that’s at least several POUNDS of bacteria that we’re carrying around (isn’t that a fun fact? You’re welcome.). The largest percentage of these live in our gut, but they are also present on our skin, hair, and in other bodily crevices. I will be using this term interchangeably with “flora”, and “microbiota”.
  • Probiotics. Live bacteria and other organisms (such as yeast) that have shown benefits to human health. I find that my clients often think of supplements when I mention probiotics, but some of the best sources actually come from whole foods. More on that later.
  • Prebiotics. Dietary fibers that are not digestible by humans, but are metabolized as fuel by our gut flora. It is important to note that while all prebiotics are fiber, not all dietary fiber is considered prebiotic. Examples of prebiotic fibers are inulin, oligofructose (OF), lactulose, and resistant starch.

Sources of Probiotics


Walk into any health foods store or pharmacy, and you’ll find no shortage of commercially prepared probiotic supplements. And in full disclosure, I do give supplements to my family. But I consider them just that, supplements. Like any good dietitian will likely attest, getting your nutrients from whole food sources is always best. This isn’t any less true when it comes to probiotics. Why? Because they only work if they are still alive when you eat them. Probiotics tend to have a relatively short shelf life, and are can be easily destroyed by heat and acidic environments.

Some of the best, and most widely accepted probiotic food sources are dairy products. Yogurt is the most common choice, and generally the easiest to find. But also improving in popularity is a creamy fermented dairy drink called kefir. Dairy is one of the best probiotic delivery agents, as it tends to protect its living cargo from highly acid stomach acids. Other than dairy, pickled and fermented foods are also thought to contain some probiotics. Examples are kimchi (spicy fermented vegetables that can be used as a condiment), sauerkraut, tempeh, and miso.

Sources of Prebiotics


Identifying food sources of prebiotics is a bit less obvious. Some more common examples include oats, soybeans, leeks, dandelion, flax & chia seeds, asparagus, garlic, and onions. Select fruits contain prebiotic fiber including green bananas (which are high in resistant starch), and apples (which are high in pectin).

Like probiotics, prebiotic fibers can lose their effectiveness when subjected to heat. So consuming them raw and minimally processed whenever possible is important. We are big fans of overnight oats here at foodnag central, which is a tasty way to keep your oats raw. Other examples would be no-bake granola, smoothies with raw oats & chia seeds added, and dips or salads with raw onions, leeks, or garlic. For extra credit, replace some of your usual salad greens with dandelion greens for a prebiotic powerhouse!

Should you be consuming probiotics?

Probably, yes. In light of all the potential benefits, with very little documented risk, probiotics are a fairly safe bet. For those with gastrointestinal complaints, including bloating, gas, and constipation, probiotics have well-known benefits. And the evidence keeps mounting regarding their relationship to human immunity, weight control, mood, mental sharpness, and reduced risk of cardiovascular disease, cancer, and type 2 diabetes.

Bottom Line.

It’s not usual for us humans to think of bacteria in a negative light. Disease causing, and dangerous. And of course, some are. But more often than not, bacteria and humans maintain a perfectly symbiotic relationship. So love your gut today, and all those pounds of bacteria in it.



Photo Credits

Kimchi: Photo by Jakub Kapusnak
Yogurt: Photo by Alison Marras
Bananas: Photo by chuttersnap

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