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Gut Health - Probiotics, Synbiotics and Fermented Foods

You now know all about probiotics but what about prebiotics and what about synbiotics? What are these and how are they different from probiotics? And how are the effects of all of these different from fermented foods?

These are all great questions, and we'll address them all but, in this blog, we’ll first discuss the prebiotic concept. Let’s start with the basics, what is a prebiotic?

Prebiotics are the foods that feed the probiotic bacteria in your gut, you know those fibers your body can’t digest but your gut bacteria love. These fibers are all prebiotics. In addition to feeding your body and your cells you also need to feed the bugs in your gut so they can produce all of those great by products our body needs, like short chain fatty acids, vitamins & minerals.

Like any other living creature probiotics can’t survive without food, make sense, right?


Think of the gut as a garden, prebiotics are the fertilizer, and the bacteria are the plants. Your plants need fertilizer to grow.

The benefits of prebiotics include:

  • Increased calcium absorption, leading to improvement in bone density

  • Increase magnesium absorption

  • Positive effects on the immune system

  • Lower cholesterol

  • Improved insulin sensitivity

  • Support with weight loss

Prebiotics can also help reverse non-alcohol fatty liver disease and can have a positive effect on gut barrier function or leaky gut. Well, that’s a lot of benefits. But it’s important to point out that simply taking prebiotics won’t necessarily result in these effects. Remember prebiotics are food for your bacteria so in order for them to do their job you have to have an adequate number of probiotic bacteria to feed.

Three important things to know about prebiotics:

  • They are not absorbed in upper GI tract

  • They must resist the acidity of the stomach

  • They have the ability to be fermented by intestinal bacteria

All fruits and vegetables are prebiotic because they contain soluble fiber. Fiber is a broad category and there are many different types.

Soluble fiber is the kind that absorbs water and forms a gel like substance. Imagine oats after they have been soaked overnight. Soluble fiber is broken down and fermented by the bacteria in the colon, therefore, making it a prebiotic.

Wheat has mostly insoluble fiber and is not a prebiotic. So, individuals who avoid wheat or gluten are not at a loss for soluble fiber because of their abstinence from wheat.

Oats are about half insoluble fiber and half soluble fiber.

The husk of psyllium is mostly soluble and therefore, is a prebiotic fiber. But psyllium doesn’t seem to work as well for women as men and it can be quite the laxative. So, it’s not our favorite prebiotic even if it is high in soluble fiber.

Fruits and veggies that are high in prebiotics include:

Chicory Root Tea
Chicory Root Tea
  • Jerusalem artichokes

  • Raw leeks

  • Raw garlic

  • Chicory root

  • Asparagus

  • Raw onions

  • Raw dandelion greens

  • Banana

  • Kiwifruit

The best-studied and most effective type of prebiotic soluble fibers are those containing inulin.

If you read food labels you may have noticed that inulin or fructo-oligosaccharides is listed as an additive in many processed foods. Why is that? Inulin tends to be low calorie and is used as a replacement for fat and sugar. However, this does not provide the same health benefit as eating inulin naturally found in wholefoods because this type of inulin has gone through an extraction process. Even when looking for a supplement it’s best to stick with wholefoods and concentrated forms rather than extracted nutrients. So, look for chicory root on the label rather than inulin if you are paying attention to fiber in foods. Chicory root naturally contains inulin.

Fructo-oligosaccharides are made up of plant sugars linked in chains. They are taken from asparagus, Jerusalem artichokes, and soybeans, or produced in the laboratory. People use these sugars to make medicine. Fructo-oligosaccharides are used for constipation, traveler's diarrhea, and high cholesterol levels.

Whether you are taking a supplement or consuming prebiotics through food, 2-6 grams a day is considered a good amount.

If given the choice between a powder and a pill we find powder to be more advantageous because the body doesn’t have to do the extra work of breaking down a capsule.

Do prebiotics feed the good guys only? This is a great question and in fact it’s been debated. The definition of prebiotic implies that if it doesn’t promote health it’s not a prebiotic but there are some studies that show they can feed some pathogens. It’s good to know about these discrepancies but for the most part prebiotics seem to encourage the growth of beneficial bacteria such as Lactobacillus and Bifidobacterium. Overall, they are certainly worth eating.

Specifically, there are two ways that prebiotics seem to benefit good bacteria exclusively:

  1. Prebiotics lower the pH of the intestines by feeding the bacteria that produce lactic acid. The low pH wards off pathogens, which tend to grow in higher pH environments.

  2. When the levels of good bacteria grow, they produce antibacterial molecules that ward off bad bacteria.

But as always you need to see how you feel as everybody is different. People with extreme dysbiosis may need to achieve more balance before incorporating prebiotics into their routine.

Side effects of prebiotics can include gas, bloating, and digestive discomfort. This is normal for the first few days but if these symptoms don’t go away this could be a signal that your gut isn’t strong enough for prebiotics yet.

People with SIBO or IBS or those that are on a low FOBMAP diet should not take prebiotics. These individuals will benefit from staying clear of fermentable fibers until their gut is stronger.

What happens in the case of SIBO, is that the prebiotics may feed the bacteria in the small intestine which is not a place we want our bacteria to be. And the main premise of the low FOBMAP diet involves avoiding fermentable foods. Individuals who can benefit from this diet don’t have enough good bacteria to feed yet.

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are short-chain carbohydrates (sugars) that the small intestine absorbs poorly. These are the scientific terms used to classify groups of carbs that are notorious for triggering digestive symptoms like bloating, gas and stomach pain. FODMAPs are found in a wide range of foods in varying amounts.

This leads us to our next topic Synbiotics which we will discuss in our next blog post.

Remember always consult with your doctor before taking or trying a probiotic supplement to make sure they are right for you.


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