– Critical For Health? or Mainstream Myth? –

Dr. Al Danenberg Nutritional Periodontist

August 14, 2022 [printfriendly]

The push is on for fiber. We are repeatedly told …

  • Eat fiber to be healthy.
  • The more, the better.
  • Without fiber, your gut bacteria will die.
  • If you’re constipated, eat more fiber.

At times, fiber is a food for some of our gut’s garden of bacteria. But our gut microbiome can function fine with minimal fiber. Why is that?

The human body was not designed to consume large amounts of fiber. In fact, large amounts of fiber could cause intestinal damage. So, why the huge emphasis on eating large amounts of fiber?

So, the question: “Is fiber critical for health?”

The answer is: “NO!”

Let’s dig in …



Humans are omnivores. That means we can eat almost anything. Our body requires nutrients that can be absorbed and utilized by our cells, and the source of these nutrients can come from plants of all types and animals of all types. However, the most diverse and bioavailable nutrients come from eating animals, nose-to-tail. In addition, the human brain owes its superior development to the consumption of marine and land animals.[1],[2]

Over the course of human evolution, the human digestive system has become efficient in digesting mostly animals and only a few plants.[3] And now this fact has been proven by a group of researchers at Tel Aviv University in Israel and at the University of Minho in Portugal. They published their cutting-edge research in March 2021 in the American Journal of Physical Anthropology.[4]

The researchers in this March 2021 paper stated, “It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality. Our study is both multidisciplinary and interdisciplinary.”

The investigators used genetics, metabolism, physiology, morphology, and archaeology of tool development to settle the question: “Were Stone Age humans specialized carnivores or generalist omnivores?”

The scientific team came to this conclusion: Stone Age humans were specialized carnivores until about 20,000 years ago. Then, some plants were brought into their diet.

The human stomach is extremely acidic to help the digestion of animal foods and kill off ingested microbes.[5] Our small intestine is relatively longer than that of most other primates. Our longer small intestine is better designed to digest animal proteins, fish, eggs, and some cooked plants compared to the shorter small intestine of other primates.

In addition, primates other than humans have a cecum that helps them ferment plant foods into energy. Humans don’t have a cecum large enough to do this. Finally, the human colon is shorter than that of other primates whose longer colon is ideal for handling plants. So, the human digestive tract is designed to eat more animal-based foods than plant-based foods. Therefore, humans are not designed to consume and digest a large quantity of fiber.

However, as I stated, humans can eat almost anything – plants and animals alike. It is interesting to note that researchers determined from fossil remains that Neanderthal Man was mostly carnivorous.[6] And new evidence has been uncovered that the world’s oldest homo sapiens in Morocco predominately ate meat on a regular basis.[7]


The Gut & Fiber

It also is a fact that the food we eat directly affects the gut microbiome. Humans have approximately 38 trillion microbes but only about 30 trillion human cells. And most of the 38 trillion microbes reside in the gut.[8]

In this 2014 study published in Nature[9], researchers showed that the short-term consumption of diets composed entirely of animal or plant products rapidly alters the gut microbiome. In fact, the gut microbiome made significant changes within 24 hours based on the types of food consumed. The investigators proved that the garden of bacteria in the gut can rapidly respond to an altered diet, facilitating the diversity of human dietary lifestyles.



Many researchers in the plant-based world suggest that one of the reasons we should eat fiber is that our colon requires butyrate to function properly. Butyrate is a short-chain fatty acid (SCFA) that is one of the byproducts of fiber fermentation via the gut microbiome. SCFAs support digestive and immune health by providing the energy our gut lining needs to function and regenerate. They also support the health of the mucus layer in the gut.[10]

But a paper published in 2019[11] showed that our gut bacteria can create necessary short chain fatty acids from both fermentable fibers as well as amino acids. In addition, collagen and other parts of the animal eaten from nose-to-tail can provide the same SCFAs as plant fibers do. In addition, a diet consisting mainly of animal fats and other animal products with minimal carbohydrates will produce ketones. Ketones can function like SCFAs.[12]

In other words, we can get the benefits of butyrate and other SCFAs without consuming large amounts of fiber-laden plants.



Researchers have reported that fiber helps the gut microbiome to increase in number and different types of species. This measurement of diversity is called “Alpha Diversity”. A high alpha diversity can improve the health of the gut and crowd out potentially pathogenic bad guys.

However, a 2018 study[13] shows that fiber will not increase alpha diversity. And trials with a zero-fiber carnivore diet do not show decreased alpha diversity.[14]

The notion that we need plant fiber for a “healthy” microbiome is fundamentally incorrect.



Some nutritionists believe that we will become constipated without fiber. But in a study published in 2012, the authors concluded, “contrary to popular beliefs, reducing or stopping dietary fiber intake improves constipation and its associated symptoms.”[15] The researchers showed that excess fecal volume from eating large amounts of fiber could place a strain on the lining of the intestine and colon. The strain could create constipation, bloating, and gas. Harsh fiber also could cause excess mucus production to protect the epithelial barrier from the irritating fiber.



Existing primal societies who continue to eat and live the lifestyles of their primal ancestors have thrived on a predominately animal-based diet with little plant fibers. When these peoples were eating a high animal-based diet, they had little-to-no chronic diseases, tooth decay, or periodontal disease. Examples are …

  • Hiwi: From Venezuela and Colombia whose diet is 75% animals
  • Ache: From Paraguay whose diet is 78% animals
  • Inuit: From the Artic whose diet is 96% marine animals
  • Hadza: From Tanzania whose diet is 48% animals

However, this was only true while they continued to adhere to their ancestors’ way of eating and lifestyle. Unfortunately, things have changed for many of them. One example is the Inuit who are suffering from chronic diseases of all types in recent years since they have adopted a processed food diet and poor lifestyle choices.[16]


Better Belly Blueprint

My Better Belly Blueprint is a blend of the popular ancestral ways of eating – Paleo, Keto, and Carnivore. By following the Better Belly Blueprint way of eating, you will be eating wild-caught and pastured animal products from nose-to-tail. These would take up at least 70% of the volume of your plate of food. The remaining 30% or less of your plate of food would consist of some raw honey, maybe some seasonal and local fruits, and very few if any vegetables. These food selections are purposely devoid or very low in antinutrients (i.e. phytates, lectins, and oxalates). Antinutrients interfere with the gut microbiome, the gut epithelial barrier, and the proper absorption of nutrients and minerals.

This lifestyle way of eating consists of high-fat and moderate-protein portions. You should consume a 2:1 ratio of fat to protein (2 grams of fat for every gram of protein). There is minimal fiber in the Better Belly Blueprint.


Eat As If Your Life Depends On It

My new book, Eat As If Your Life Depends On It, will be published in a few weeks. It will be available in paperback and hardcover. In it, I describe how and why I blended the keto. paleo, and carnivore styles of eating into one ideal eating lifestyle – my Better Belly Blueprint.  I’ll show you how to track your foods with your personal 3-Day Food Journal, how to transition slowly into this lifetime way of eating week-by-week, and how to navigate the adaptation period of changing your old eating habits. You’ll be transformed into a well-nourished, energetic, cognitively alert individual. Also, you will enhance your immune system to become as robust as possible.

I’ve written this from my heart and from the lessons I’ve learned along my cancer journey. This is a book that should be a model for the human species to survive and thrive. I offer it as my legacy that I want to share with the world.


















If you don’t want to miss out on new posts, sign up for my Free “Belly Bites” Newsletter and receive your free copy of Dr Al’s “5 Things That Could Be Impacting Your Health Right Now” HERE.


Recommended Posts


  1. Looking forward to reading your book Dr. Al and sharing it with family and friends! I love that your book will walk folks through the transition to this ancestral way of eating because that’s the hardest part. It is also very difficult for us to overcome the brainwashing we’ve been subjected to since children where we were told constantly to “eat your vegetables”. Your personal story and new book will be the greatest legacy you leave behind. Thank you Dr. Al for caring and sharing.

  2. The hypothesis about fiber not being necessary in the human diet is being raised with increasing frequency. It truly is a mind-blowing one, due to the tremendous amount of marketing and propaganda of the last 50 years or so. We’re all entitled to our own opinions but not our own facts, and the facts seem to be stacking in favor of a no-fiber diet. I too am looking forward to reading your book and sharing it with others, though I believe in adaptation of life forms rather than evolution.

  3. Excellent coverage of the essentials!
    According to Dr. Mc Bride creator of the GAPS nutritional protocol. Fibre is extremely difficult for the human body to digest and feeds both pathogenic and beneficial microbes equally. It therefore should be avoided until you have sufficiently healed and sealed the gut wall and even then the foods must be prepared adequately: fermented, cooked very well or juiced.

  4. I can’t wait to get your new book!! Thank you for doing this important work!!

  5. A question… I’ve read a diet book similarly based ancestral eating habits… that actually made some distinctions on best diets based on blood type and differences in diet as the blood type(s) and corresponding eating habits developed.
    In the book, type O was the original blood type, probably closer to the Neanderthal blood type and diet, was similar to the diet you suggest..

    So, I’m wondering if other blood types would need to modify the proportions of protein and vegetable, etc.

    Also, what can you do reduce the effects of the brouculli and zucuni anti nutrients…

Comments are closed for this article!