The Secret of Prebiotic foods & fiber

The Secret of Prebiotic foods & fiber

Most people don’t know that you need to feed the good bacteria in your gut. “Prebiotic” fibers are the food that the good bacteria require in order to colonize your gut – and to be able to thrive and flourish. These fibers are indigestible to us, but necessary for good bacterial balance.

In my opinion, one of the biggest misunderstandings about gut health is not about whether “PRO-biotic” supplements help. Instead, it’s the lack of information about the importance of consuming “PRE-biotic” foods — what they are and how critical they are to our health.

From research, we understand that the good bacteria in our gut must have the right kinds of fiber (nutrition) in order to colonize the gastrointestinal tract and be able to establish themselves and thrive. And, surprisingly, this information would argue that it really doesn’t matter how many PRO-biotic supplements you take… Without also feeding the good bacteria that you are adding in a supplement form, the bacteria can not get established.

Fiber is critical. And knowing which foods contain beneficial Prebiotic fibers, and how to include them in your diet, is key!

Economic trends show the rising sales of Probiotic foods & supplements.

As people search for information and products to help to improve their nutrition, the Health and Wellness movement continues to gain attention. An indication of this wellness trend is the recent announcement by mega-corporation General Mills, Inc. They have invested 12 million dollars into “Good Belly”, a company that manufactures probiotic snacks and beverages. This is an interesting economic vote regarding the popularity and interest in the gut microbiome and gut bacteria.

The buzz around various Gut Health Improvement programs, and health products to support your microbiome, are rapidly gaining popularity. The global sales of probiotic products are projected to exceed 63 billion US dollars by 2022. (1)

Meanwhile, even with this economic trend, there is still controversy about the benefits of taking Probiotic supplements. I think that perhaps part of the reason that Probiotics may not show significant health improvements for so many people may stem from the misunderstanding of the importance of Pre-biotics. I believe this could be a missing piece in many programs that teach techniques to improve gut health.

What are the differences between Pre-biotics & Pro-biotics?


Prebiotic Foods and Fiber
Probiotic supplements provide good bacteria colonies for the digestive tract.

PROBIOTICS are the living microorganisms that live within certain foods. They are the “good-for-you” bacteria and these bacteria have been utilized in traditional foods from many cultures throughout history. Sources of Probiotics include fermented foods such as kimchi, miso, sauerkraut, yogurt, and kefir. Probiotics are also in many supplement forms throughout the marketplace.


Prebiotic Foods and Fiber
Prebiotics provide Insoluble fiber.

Meanwhile, PREBIOTICS are the foods and fiber that help to maintain balance and feed the helpful gut bacteria. These are the non-digestible foods that our gut microbes eat and require to survive. Common food sources for these fibers include garlic, onions, wheat, oats, bananas, leeks, chickpeas, chicory root, and artichokes. (2)


The Wild World Within.

My first exposure to the concept of Prebiotics came from an article in the Eating Well Magazine (July/August 2014 issue), titled: “The Wild World Within” written by Gretel Schueller. (3)  I still have a ragged and well-worn photocopy of this article in my files, and I have passed it on to many friends over the years.

In this article, Scheuller interviews scientist, researcher, and back to the earth enthusiast, Jeff Leach. Leach’s book, Bloom: Reconnecting with Your Primal Gut in the Modern World, cites research linking gut microbes to everything from autism and depression, to cancer and diabetes, to heart disease and obesity. In addition, Leach is responsible for founding the “Human Food Project”, which is a global effort to study how diet affects the microbial world within us.

Listen to an interview with Jeff Leach from High-Intensity Health, By

“Nothing is more important than feeding our gut microbes”.

According to Leach:

“We should start thinking about diets from the perspective of what we should be feeding our gut microbes, nothing matters more.”

Leach speaks not only about his research but also from his own personal experience. And he argues that “just one day is enough to dramatically shift the gut microbiome”. Leach has personally tried many different diets (fermented foods, paleo, raw, vegan, and others). He then tested his own stool samples to see what happened to his microbiome. Subsequently, Leach also refers to a study published by Nature that compares gut health and gut bacteria. This study monitored people eating an entirely animal-based diet (meats, cheese, eggs) with a completely plant-based diet (grains, legumes, vegetables, and fruits). As a result of this research, Leach concludes that “one day on either diet was enough to dramatically shift the gut microbiome of participants”. (3)

“Fiber is the game-changer.”

“It’s the fiber that’s the game-changer”, says Leach. He recommends adding 40-60 grams of fiber per day to shift the gut microbiome toward a diverse, more beneficial mix of microbes. He talks about the fact that the gut microbes digest fibers through a fermentation process, which produces short-chain fatty acids that provide energy and nutrition for the good bacteria.

Leach goes on to discuss the types of fibers, saying that fibers come in varying lengths and that most of the fibers we eat are too short to survive the digestion process and in order to arrive intact to the beginning of the large intestine (aka colon) where the good bacteria live. The two fiber types that are long enough to survive the length of our digestive tract are “fructans” and “cellulose fibers”

  1. Cellulose fibers are the tough parts of fruits and veggies that we tend to throw away, including the stalks and stems of broccoli, the bottoms of asparagus, carrot peels, and the stringy parts of celery.
  2. Fructans are the fibers found in many fruits and vegetables like leeks and onions, as well as fruits such as raspberries, watermelon, and more.

Prebiotic Foods and Fibers

Eat one leek a day!

Cooking time also matters because heat breaks down these important fibers.

Leach recommends eating one lightly cooked leek a day as one of the healthiest things you can do. The white part stores fructans and Dr. Leach’s argument is that this “probably does more good for you than a wheelbarrow full of yogurt”. Meanwhile, the green top of the leek contains cellulose which is also a very helpful fiber.

“If you eat one entire leek – the whole thing, from muddy fibrous roots to green tops – this could change your microbiome in 48 hours”. (Jeff Leach) (3)


This is Jeff Leach’s list, foods are ordered in terms of grams of fructans present.

(Remember that there are many other nutritional benefits to these foods, but when we focus on nutrition for your gut microbiome and good bacteria, this is an excellent list.)


47 g. – 1 c. Jerusalem artichoke

29 g. – 1/2 c. chicory root

10 g. – 1 leek

9 g. – 1 c. white onion

6 g. – 1 c. raspberries

6 g. – 1 c. cooked beans

5 g. – 5 asparagus spears


3 g. – 6 cloves of garlic

1 g. – 1/2 c. wheat bran, 1 nectarine, 1 medium banana, or 1 pear


0.7 – 1 c blueberries

0.7 – 1 c. broccoli

0.3 – 1 c. kale

0.2 – 2 c. red leaf lettuce

0 – tomato, carrot, and green lettuce.


There are many types of fibers that have been discovered in plants, including various types of starches, lignins, cellulose, and others. Early on, these fibers were only of interest to plant chemists, not to physicians. But then in the 1980s, it was discovered that fiber could broadly be separated into insoluble and soluble types. No fiber is actually digested by the small intestine. All of it arrives in the colon unchanged.

Insoluble fiber does not dissolve in water, is not fermented or broken down by colon bacteria, but does retain lots of water in the colon and so provides a larger, softer stool.

Soluble fiber, on the other hand, is broken down and fermented by colon bacteria. However, we learned more about these two types of fiber in the 1990s when better measuring methods were devised. We now know that the difference between these two fibers, insoluble and soluble, is important, particularly with the discovery of prebiotic soluble fibers and how can they are beneficial to the microbiome and gut health. (4)

Soluble vs. Insoluble Fiber:

The solubility of a fiber refers to its ability to dissolve in water. Based on this, fibers are often categorized into two types, as either soluble or insoluble fibers.

  • Soluble fiber blends with water in the gut, forming a gel-like substance. It can reduce blood sugar spikes, and has various metabolic health benefits. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It is also found in psyllium, a common fiber supplement. Some types of soluble fiber may help lower the risk of heart disease. Soluble fibers include gums, pectins, psyllium, beta-glucans, and others.
  • Insoluble fiber does not blend with the water and passes through the digestive system mostly intact. It functions mostly as a “bulking” agent and may help speed the passage of food and waste through your gut. These fibers are in foods such as wheat bran, vegetables, and whole grains. They add bulk to the stool and appear to help food pass more quickly through the stomach and intestines. These insoluble fibers include lignin and cellulose. (4)

Daily recommendations for fiber in your diet:

Estimates are that people in the United States get less than half of the recommended fiber each day. These are the recommendations for daily dietary fiber intake (including both soluble and insoluble fibers, which does include the prebiotic foods and fiber):

  • Men, age 50 and under = 38 grams per day
  • Women, age 50 and under = 25 grams per day
  • Men, over 50 = 30 grams per day
  • Women, over 50 = 21 grams per day  (5)


Dr. Mercola also writes about fiber and probiotics. Similarly, he offers that soluble fiber can help reduce your risk of premature death from any cause, including type 2 diabetes, heart disease, stroke, and cancer. (6)  In addition, Dr. Mercola mentions that most people have heard about the importance of eating fibers, particularly soluble fibers. However, he adds that few actually understand the benefits of insoluble fibers, or realize that they do more than just correct stool formation or help the body to process food.

Many of the prebiotic foods and fiber that are indigestible to us are the exact food that our good bacteria require.  And, it is these types of fibers that are some of the most critical pieces in supporting the health of our microbiome.


Prebiotic Foods and Fibers

Gut health expert Allison Knott, a registered dietitian and board-certified specialist in sports nutrition, has written an article for Eating Well magazine titled, Gut Health: Prebiotics, Probiotics, and the “Forgotten Organ”. (2) (The forgotten organ is your gut’s microbiome.) Knott opens by saying that your stomach does more than just digest food. And like others, she offers that having a healthy microbiome is a key to unlocking better health. 

In addition, she writes that “not everyone’s gut microbiome is the same, nor should it be. As a result of this, she mentions that some of the known influences on an individual’s microbiome composition include genetics, type of delivery at birth (cesarean section vs. vaginal birth), antibiotic use, age, health status, geographic location, stress level, the frequency of exercise and diet”. In summary, Knott adds that “while some factors are out of your control, others can be influenced by diet and lifestyle”.

Diet alone can alter your Microbiome!

Knott also agrees with Leach about the importance of how the food we eat influences our gut microbiome:

“The good news is that bacteria can be altered by diet alone.” And furthermore, Knott argues that this means you do not need to purchase over-the-counter high dose probiotic supplements to improve your gut health.”

However, it is important to mention that Knott also notes that there are exceptions to this rule. These exceptions include people with chronic conditions such as IBS or Chron’s, as well as people who are taking high-dose antibiotics or have another condition that impacts the GI tract. Above all, Knott recommends that if you have any of these conditions, you should talk to your doctor about the best way to boost your gut bacteria. (Before adding the prebiotic foods and fiber recommended in this post.) (2)

Click here to learn more about the TGH 30-day reboot and how to improve your microbiome by altering your diet!

Prebiotic foods and fiber are something that most Americans are not getting in sufficient quantities. However, many experts warn against adding too much fiber, too quickly to your diet. This may cause bloating and discomfort. Furthermore, there is also concern around adding fiber if you have serious gastrointestinal issues or conditions. Please consult with your medical provider if you have any concerns about adding dietary fiber to your daily routine.

Peg Desrochers

True Gut Health

Live a Vibrant Life!

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