Wednesday, October 19, 2011

PREBIOTICS: Food for Healthy Gut Flora

Prebiotics are the dietary soluble fibers that the good gut bacteria ferment into short chain fatty acids (SCFA) which have many beneficial effects in the human body, including reducing inflammation. They create conditions that favor healthy gut flora, especially probiotic bacteria from the bifidobacteria and lactobacillus genus.  To be clear, prEbiotics feed prObiotics.

Munching your bowl of Raisin Bran, you may think you are getting your daily fiber, but the scant amount of fiber in our diets is mostly insoluble fiber or roughage which is not nearly as beneficial as soluble fiber. The average American eats only 3-4 grams a day of soluble fiber. Most sources recommend at least 5-10 grams of soluble fiber a day with a warning to slowly build the amount of fiber in the diet as it might cause uncomfortable gas and/or diarrhea if you eat too much before your system adjusts. This seems like a paltry amount in view of the latest findings about our Paleolithic ancestors. Archeological finds in the desserts along today’s Texas-Mexican border reveal that prehistoric man ate an estimated 135 grams a day of prebiotic soluble fiber. Could our drastically reduced consumption of dietary soluble fiber in modern times explain the current epidemic of chronic diseases like obesity, diabetes, heart disease and cancer?  Let's look at the known benefits of soluble fiber:

Benefits of Prebiotic Soluble Fiber
  1. Promotes the growth of beneficial probiotic bacteria and discourages the overgrowth of pathogenic bacteria.
  2. Slows absorption of glucose and reduces insulin resistance improving blood sugar control. May prevent diabetes and other metabolic disorders.
  3. Improves lipid profile lowering LDL cholesterol and triglycerides while raising HDL cholesterol which may reduce the risk of heart disease.
  4. Prevents inflammation of the intestinal lining and leaky gut syndrome. May prevent or improve chronic inflammation.
  5. Helps regulate the immune system preventing infections and autoimmune disorders like allergies, asthma and eczema, and serious autoimmune diseases.
  6. Stimulates intestinal fermentation of soluble fiber into short-chain fatty acids, like butyrate, which may be the root cause of the above mentioned benefits.
You may recall my story of the lab rats which were shown to convert soluble fiber into short chain fatty acids (SCFA), especially butyrate. Higher levels of butyrate measured in human feces are the main indicator of good gut health. As the healthy bacteria flourish in the intestine, they occupy the forest of hair-like protrusions called villi that line the intestine, and keep the bad bugs out of the neighborhood. By producing butyrate, the probiotic micro-organisms signal the immune system that all is well and restore balance preventing any autoimmune attacks that might lead to chronic inflammation in a confused and unbalanced gut environment.

So, how does modern man get more soluble fiber into our diet to get our gut flora back to Eden?

Normal Dietary Sources of Soluble Fiber
As previously stated, the standard American diet (SAD) does not contain much soluble fiber. Among the common foods, the best sources of soluble fiber are: beans, peas, lentils, barley, oat bran, sweet potatoes, onions, garlic, broccoli, citrus fruit, pears and apples. Frankly, it would be hard to get more than five grams a day of soluble fiber eating these foods. For a diabetic, many of these foods contain too much carbohydrate that might adversely affect one’s blood glucose levels. If you are concerned about good gut health, consider adding specialized soluble fibers known to be concentrated sources of prebiotic fiber.

The two prebiotics that are most commonly used as supplements are FOS (fructo-oligosaccharides) and inulin which is usually extracted from chicory root or Jerusalem artichoke. These are powerful prebiotics, so I would not attempt any prehistoric doses at the onset. I read that a therapeutic dose could be over 20 grams/day, but one should start much lower. So, I took 2 grams the first day and 20 grams on the second day. Wow! Talk about a gut feeling. My relationship with my wife was less than harmonious as she was serenaded all night by the wind section.

Some bacteria also makes hydrogen and methane when they ferment soluble fiber and some bacteria consume hydrogen and methane. It takes awhile for the trillions of bacteria in our gut to adapt to their new roles. I recommend starting by adding just 1 gram of FOS and/or inulin to your dailly coffee, tea or favorite beverage ... and gradually ramping up. FOS and inulin are slightly sweet and water soluble. They are often blended with artificial sweeteners to provide a more balanced sweetness and better mouth feel.

I now consume at least 10 grams a day of FOS and 15 grams a day of inulin.  FOS ferments relatively fast in the upper portion of your intestine while inulin ferments more slowly in the lower sections of your intestine.  Combining these two powerful prebiotics distributes the benefits throughout your gut ... and I feel great!  Despite my conscious effort to consume more prebiotic soluble fiber, my experiments have shown that if I attempt to eat paleolithic levels of soluble fiber (>100 grams/day), I will still suffer flatulence and diarrhea.  It appears that some of the super probiotic bugs that inhabited our paleolithic ancestors' guts may now be extinct.  Again, gradualism and moderation is the way to approach prebiotics.  I also believe in a diverse source of soluble fiber in the diet.

Psyllium seed husk is the premier source of the soluble fiber mucilage. It is 71 percent mucilage and nine percent insoluble fiber. It is sold as the popular bulking agent Metamucil which is used principally as a laxative. Some of the best food sources of mucilage are flax seed and chia seed which can both be ground as a flour and used as a wheat flour substitute for low net carb and high fiber baked goods. Very tasty. Okra, called Lady Fingers in parts of Asia, is a vegetable that is high in mucilage. Several cacti are rich sources including aloe vera and agave. Fenugreek, a seed used as a seasoning in Indian food, is another good source. Kelp consumed as a sea vegetable has lots of mucilage as well as iodine and carrageen is another seaweed source derived from Irish Moss. Slippery elm bark, which is an herbal remedy for many gastrointestinal disorders, has mucilage as its primary active ingredient.

This prebiotic fiber can be found in small amounts in some fruits and vegetables. Commercial pectin is derived from citrus peel which is about 30% pectin and the pomace that is left after apples are pressed for juice or cider. Pectin is used as a gelling agent in jams and jellies and as a thickener in many processed foods. Pectin sold for making jams and jellies often has added sugar, but it can also be found in its pure form as a nutritional supplement.

Many gums are used by the food processing industry as jelling agents and thickeners. The most common are guar gum, gum Arabic (acacia senegal gum) and xanthan gum. They are also sold as gluten substitutes for people who have gluten intolerance to use in baked goods.  Some Celiacs, however, cannot tolerate these gums. People with sensitive guts sometimes find these vegetable gums irritating, so I no longer recommend them.

The prebiotic fiber beta-glucan is regarded as very effective for modulating immune response. Extracts derived from bakers’ yeast and some medicinal mushrooms are marketed as nutritional supplements. Reshi, Maitake and Shiitake mushrooms are Asian culinary delicacies especially high in beta-glucan that are noted for their medicinal effects. Oat bran and barley are a more common source of beta-glucan but also contain a large amount of starch which quickly converts to glucose in the body.

The soluble fiber gluccomannan comes from the konjac root, a yam-like tuber. Its flour is used to make noodles and fruit jellies in Asia. Because of its ability to quickly absorb lots of water, it is sometimes used as a weight loss supplement that gives one a feeling of fullness. This same characteristic has resulted in some rare instances of capsules of glucomannan expanding too quickly in the body resulting in dangerous blockages. It is best consumed as the traditional Asian translucent noodle called "shirataki" in Japan and "mo yu" in China which is available at most Asian grocers.

Other Non-Starch Polysaccharides
Agar agar is a polysaccharide extracted from red algae that is used as gelling agent (vegetarian gelatin). It is best known as the medium used in petri dishes to grow cultures in labs. It gels liquids at a lower temperature than gelatin and is much firmer. It makes a really great aspic.

Resistant Starches
The principal source of soluble fiber in most Western diets is resistant starch from sources like beans, barley and oats, and to a a lessor extent, whole grains.  These are starches that are not fully digested in the upper intestine and are fermented in the lower intestine.  One problem ... RS is always accompanied by other starches which are quickly metabolized into glucose.  All the above legumes and grains also contain phytic acid which is an anti-nutrient that blocks the absorption of many beneficial nutrients.  Healthy people can eat moderate amounts of legumes and grains, but I know of no resistant starch source which I can recommend to those suffering from obesity, diabetes or any metabolic disorder.

As you cultivate healthy gut flora, think of probiotics and probiotic yogurt as the seed of your emerging health, and prebiotic soluble fiber as the fertilizer to help the good bacteria thrive.  Remember that the opposite of prebiotics is fructose and other simple carbs which are unhealthy nutrients that feed bad bacteria and yeasts.  Unless you are living like a prehistoric hunter-gather in the Chihuahuan Dessert dining on the local cacti, you will be doing very well if you can consume 20+ grams a day of soluble fiber.


  1. Denny,

    Thanks a lot for this very informative post. I had a very positive experience with good gut flora recently. Grocery stores here stock probiotic yogurt starter but it seems to be a highly irregular affair -- when I tried to buy the yogurt starter I couldn't find it in any of my nearby grocery stores although they all assured me that they do carry it. But in one of the stores I found enteric coated probiotic capsules and bought a packet containing 20 (it was $40 for the packet.) I have been taking one capsule a day for the last two weeks. I have to say my irritable bowel has calmed down a lot. Digestion has significantly improved. And the best thing is that BG levels have also come down a bit. All this happened in a short span of two weeks. This has strengthened my belief that my "impaired metabolism" has a lot to do with the condition of my guts.

    I have been doing several things right for some time now - taking omega 3 and vitamin D supplements, increasing my consumption of chia, flax, almond flour etc, ditching Mazola for my favourite coconut oil, and so on. I think probiotics is one more step in the right direction. Let me try prebiotics now and see how it works for me.


  2. With flax and chia, you already have a fair amount of prebiotic soluble fiber in your diet. Build it up slowly so your body can adjust and go for variety.

    Isn't okra or Lady's Fingers a common vegetable in your cuisine? It is a tasty source of soluble fiber. If you want to supplement, by some inulin and put a small amount in your tea. It is very powerful prebiotic.

    Glad to hear, Rad, that so many things are working for you.

  3. hi, good points on SCFA modulation of gut inflammation but if I may ask where did you get the reference for this statement:

    "By producing butyrate, the probiotic micro-organisms signal the immune system that all is well and restore balance preventing any autoimmune attacks that might lead to chronic inflammation in a confused and unbalanced gut environment."

  4. Did you read my article here titled, "Tale of Two Rats – How Fiber Can Make You Beautiful and Healthy"? It is based on the research of Dr. Jianping Ye.

    Actually, there is quite a bit in the literature on this subject. Trying Googling "butyrate" and "inflammation" and you will get a long reading list.

  5. Very informative and well written article.

  6. i gave my son probitoics following my doctor's advice. your article confirm that i did a good thing and i probably take some myself.

  7. Great post. I am amazed that out ancestors were able to consume as much as 135 g of fiber per day. I also think that they got way more exercise than we do today. Thanks for sharing a thought provoking article.

  8. Informative post. Thanks a lot for sharing this post. Waiting for another informative post. Keep it up.

  9. Probiotics are great for healthy digestion and for keeping inflammation in the gut under control. Organic yoghurt is a great source of probiotics. My favorites are Brown Cow and Walibi.

  10. Thanks. I am not familiar with these brands. Are they widely available in the US? I live in Shanghai.

    Four characteristics of a good probiotic yogurt:

    1. It should contain some truly probiotic strains besides the normal L. bulgaricus and S. thermophilus yogurt strains. Look for some strain of Bifidobacterium, L. acidophilis and other probiotic strains that will colonize your gut.

    2. Live organisms in yogurt have a short shelf life. Yogurt should be eaten within one week of being produced. Check the date on commercial yogurt ... that is, date of production not some theoretical expiration date that may be two months after it was produced.

    3. Does the yogurt tell how many live organisms on the label? Most commercial yogurts are fermented for just 4-5 hours and have few.

    4. Any starches, gums, sugars or other unhealthy stuff in the yogurt?

    I believe homemade fully fermented probiotic yogurt is always better than the commercial stuff. See my posting on how to do it.

  11. A million thanks for your information on prebiotics. I am 74 y.o. who since early childhood has evacuated with enemas... Probiotics helped me to go to the toilet, by softening my feaces, but the real change is happening now after I have turned to soluble fiber... after reading your information on prebiotics. A million thanks. (I guess I have to wait some time to get the full benefits of the new diet/prebiotic intake).
    Thanks again
    monsie pickles, mrs

  12. Hello Denny - I am always interested in gut microbiota and health. I write a blog on immune balancing, specifically, and all the nutrition and life style dynamics that go into achieving a balanced immune function. I'll be interested in your future writings. I do think fiber is essential for feeding beneficial bacteria. I also have heard from physicians who say that unless one has special medical needs/conditions, gluten-free diets are not the way to go, especially if one is giving up good, whole-grain fiber. Anyway, thanks for the information.

  13. I love the topic. I am a chiropractor in St George UT and we have a strong retirement community here. That population shift is also seen in my patient load. As part of my discussions with patients about there treatment plans, we include the topic of inflammation. Systemic inflammation has a role in spine health. Our efforts in reducing systemic inflammation begin with diet. I try to get 25-30 grams of fiber each day. It can be a challenge to get that high.

  14. Dr. White,

    What foods do you eat to get 25-30 grams of fiber per day. I assume that includes both insoluble and soluble fiber. As my article indicates, I eat a wide variety of high fiber foods to get a variety of soluble fiber. I find that I need to add some FOS and inulin supplements to get enough soluble fiber. Do you encourage your patients to use supplements?

    Do you find that high dose fish oil significantly reduces inflammation in your patients?

  15. Good post. Sometimes it is easier to get our nutrients from food supplements. Much of the food that we eat today does not contain all that our bodies require on a daily basis.

  16. Denny, Thanks a lot for this useful article.

  17. Prebiotics are the dietary soluble fibers that the good gut bacteria ferment into short chain fatty acids (SCFA) which have many beneficial effects in the human body, including reducing inflammation. Thanks for sharing this useful list for Benefits of Prebiotic Soluble Fiber.

  18. I really like the subject. I am a chiropractic specialist in St Henry UT and we have a powerful pension group here. That inhabitants switch is also seen in my individual fill. As part of my conversations with sufferers about there therapy programs, we involve the subject of swelling. Wide spread swelling has a part in backbone health. Our initiatives in decreasing systemic swelling start with eating plan. I try to get 25-30 h of roughage each day. It can be a obstacle to get that high.

  19. this is very informative... thanks alot...

  20. This is very well written and you have included some great tips which I plan to start trying tonight

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