Do You Need to Supplement with Dietary Fiber?

Do You Need to Supplement with Dietary Fiber?People ask me, “John, what do you think about dietary supplements, especially fiber?” I tell them, “I believe you can get all of the necessary nutrition your body needs from the food you eat and there is little proof that supplements are effective.”

In my book, Surviving Cancer, I included a section on dietary fiber and my thoughts on the research around fiber & fighting diseases such as Cancer and Type 2 diabetes. I invite you to read this excerpt, watch the video that follows and get the book to learn more.


Do You Need to Supplement with Dietary Fiber?

Dietary fiber refers to edible parts of plants and can be eaten directly. It has two main components:

Insoluble fiber is not digestible by enzymes in the small intestine but provides bulk by absorbing water from the intestinal wall. Insoluble fiber provides nourishment for bacteria in the large intestine.

Soluble fiber is readily fermented in the colon to physiologically active products that are beneficial to the body. In addition, gases generated during fermentation are absorbed into the body to be released through the lungs, the rectum, or compressed to reach the level of pressure necessary to initiate elimination of waste from the body. This could be the reason why not eating enough vegetable fibers, for the needed bulk, or not providing nutrition to the right type of bacteria in the gut to produce enough gas, leads to chronic constipation in some people.

Many products are on the market claiming to contain beneficial fiber, including reducing the risk of colon cancer. There is evidence suggesting that consumption of fiber may offer the benefit of protecting against risk of progressing from prediabetes to Type 2 diabetes. Fiber might do this by delaying post-prandial (after meals) glucose absorption.

However, dietary supplementation with fiber has not been clinically proven to be beneficial in controlled studies. For example, the authors of a study using flaxseed for glycemic control observed lower A1C blood tests when people had a low-dose intervention of flaxseed. Paradoxically, there was no change when people were given a high dose of flaxseed. The authors also could not explain the absence of improvement in fasting fructosamine values (another marker of glycemic control based on glycated albumin) at low and high dose supplementation.

One caution to watch out for: Many of the dietary fibers supposedly in some products are
not actually fibrous.

Natural nuts, seeds, and legumes such as beans and peas are the most convenient and easily available sources of dietary fiber—eating them is the solution I recommend.


Many claims are made that supplements can fight cancer and diabetes. But frankly, little is known to prove it. But here is a video that shows what you can do to ensure that your body gets the nutrients you need.

Dr. John on CancerSurviving Cancer

A New Perspective on Why Cancer Happens & Your Key Strategies for a Healthy Life 

This book will be an invaluable resource for anyone who has already been diagnosed with cancer localized to a single site of origin and not yet colonized in another part of the body. It is also for anyone who believes they are at risk of cancer due to heredity, lifestyle, working conditions, stress levels, or for any other reason. And finally, this book is especially important for anyone with Type 2 diabetes, a population that is twice as likely to develop certain types of cancer compared to individuals who do not have diabetes.

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