Nothing in this paper should be considered medical advice. For the treatment of any medical condition you must seek the advice of a trained medical doctor. This paper is not written with any specific products in focus but rather as a research of what is currently known about dietary fiber in general regarding nutrition.
Dietary fiber is not well understood. There is a lot of wrong information in the public about dietary fiber but there are also many anecdotal studies that indicate that where a traditional diet of high fiber and natural foods are replaced with a modern diet of low fiber and processed foods that health deteriorates. Some studies indicate fiber may provide reduced risk of heart disease, type 2 diabetes, high blood pressure and breast and colon cancers.1 Fiber can help you lose weight by replacing high calorie, high carbohydrate foods with no calorie, no carbohydrate fiber in addition to the fact that fiber may help block absorption of calories and provide indirect biochemical benefits to the human body, regulation of the digestion process and a sense of fullness.
Traditionally all dietary fiber is from plant sources and is broken into two main categories, water soluble and water insoluble. Water soluble fibers are also called gums. All plants contain both type of fiber in various degrees. The insoluble fibers are generally the structural parts of the plant while the soluble fibers are generally the wet part of the plant. They absorb water, slow down the emptying of the stomach and make you feel full. Soluble fibers can also help lower LDL (so-called bad) cholesterol by modifying absorption.2 Insoluble fiber is considered gut- healthy fiber because it allows for easier fecal management by the body but is also digested by bacterial in the gut which produces important byproducts used by the body. Insoluble fiber is actually the largest amount of fiber we eat when eating raw, natural fruits, nuts and vegetables. Calling this fiber insoluble is not truly accurate because insoluble fiber can hold water.
A traditional whole foods diet consisting mostly of vegetables, nuts and fruits is rich in both soluble and insoluble fiber.
One of the reasons that fiber doesn’t get the respect that it should is because it is not understood. Many professionals think that fiber enters the body and exits the body mostly unchanged. That is far from the truth and in fact the effects of fiber on the body are profound. In my personal
1 Prevention Fiber Up Slim Down Cookbook by Rodale, Page VII 2 WebMD http://www.webmd.com/diet/fiber-health-benefits-11/insoluble-soluble-fiber
opinion dietary fiber should be considered an essential nutrient as critical to good health as Vitamin C.
Let’s review the assumption, that fiber enters and exits the body mostly unchanged. This has been proven to be false. First, fiber is digested by bacteria in the human gut. The amount of digestion is determined by many factors including the health of the subject and the type of fiber. For example, in a mixed diet fed to healthy individuals 70 to 80% of the fiber is digested during passage in the gut.3 Cellulosic fiber survives digestion better than water soluble fibers. The significant fact is that dietary fiber is used in the body and not expelled. In healthy individuals only 17% of the solid matter in feces is fiber but 55% is bacteria and the remainder is undigested food, water, mineral salts and dead cells.4
The liver generates bile to aid in the digestion of fats in the digestive system. Bile is made from cholesterol which is why anything that increases the production of bile decreases bloodstream cholesterol. The body generally mistakes soluble fiber as fats for the purpose of bile generation, however since fiber is not a fat it is not digested by the bile. Bile is fat soluble so it binds other fat soluble toxins in the intestines. Unfortunately instead of the bile being expelled it is reabsorbed back into the blood. This changes when in the presence of insoluble fiber. The bile salts and its load of toxins bind to the insoluble fiber which is then expelled from the body.5 This provides a triple benefit to the body. It lowers cholesterol by a natural process. It gently sponges toxins and expels them from the intestines. It acts as a stimulate for the liver and digestive processes by increasing the production of bile. Increasing the flow of bile may help to prevent the formation of bile stones.
Humans exist as a mix of human and other living organisms normally living in healthful harmony.6 Many of these organisms are bacterial and a few fungi. Even some of the harmful bacteria are now thought to provide important benefits to humans when existing in harmony.7 Beneficial microorganisms are called symbiotes. Exactly what symbiotes are needed for human health is unknown and largely unstudied.
Earlier I mentioned that bacteria use the fiber in the gut. One of the results of this bacteria digestion is the release of Inositol from phytic acid found in insoluble fiber. Inositol improves metabolism of cholesterol and helps depression, insomnia and fibromyalgia. In addition to Inositol these same bacteria create Vitamin K which helps the body manage bruising and blood clotting, Biotin (B7) and Vitamin K2. K vitamins help in the management of calcium and from
3 The Effect of Dietary Fiber on Fecal Weight and Composition by John H. Cummings 0-8493-2387-8/01 (CRC 185) 4 Dr. David Williams Alternatives May 2012, page 3 (J Med Microbiol 80;13(1):45-56)(FASEB J 91;5(13):2856-2859) 5 Dr. David Williams Alternatives May 2012, Page 5 6 http://en.wikipedia.org/wiki/Symbiosis 7 Dr. David Williams Alternatives May 2012, page 2. In addition see recent studies of Helicobacter pylori in Science News October 9, 1999. http://www.sciencenews.org/sn_arc99/10_9_99/bob1.htm
the buildup of calcium in soft tissue. Since humans are unable to store much Vitamin K this source is important.8 Without a diet rich in both types of fiber these bacteria have no food and produce no beneficial results.
This paragraph is quoted from Wikipedia. “When soluble fiber is fermented in the gut, short- chain fatty acids (SCFA) are produced. SCFAs are involved in numerous physiological processes promoting health. Some of these may be to help stabilize blood glucose levels by acting on pancreatic insulin release and liver control of glycogen breakdown, stimulate gene expression of glucose transporters in the intestinal mucosa, regulating glucose absorption, provide nourishment of colonocytes, particularly by the SCFA butyrate, suppress cholesterol synthesis by the liver and reduce blood levels of LDL cholesterol and triglycerides responsible for atherosclerosis, lower colonic pH (i.e., raises the acidity level in the colon) which protects the lining from formation of colonic polyps and increases absorption of dietary minerals stimulate production of T helper cells, antibodies, leukocytes, cytokines, and lymph mechanisms having crucial roles in immune protection, improve barrier properties of the colonic mucosal layer, inhibiting inflammatory and adhesion irritants contributing to immune functions. SCFAs that are absorbed by the colonic mucosa pass through the colonic wall into the portal circulation (supplying the liver), and the liver transports them into the general circulatory system. Overall, SCFAs affect major regulatory systems, such as blood glucose and lipid levels, the colonic environment, and intestinal immune functions. The major SCFAs in humans are butyrate, propionate, and acetate, where butyrate is the major energy source for colonocytes, propionate is destined for uptake by the liver, and acetate enters the peripheral circulation to be metabolized by peripheral tissues.”
The University of Kentucky published a paper on the health benefits of dietary fiber9. Among these benefits they found that people with a diet high in dietary fiber may be at significantly lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity and some gastrointestinal diseases. Increasing dietary fiber lowered blood pressure and serum cholesterol levels, significantly increased weight loss in obese individuals and benefited the gastrointestinal disorders of gastro esophageal reflux disease, duodenal ulcer, diverticulitis, constipation, and hemorrhoids. They also found that increasing dietary fiber in the diet improves glycemia and insulin sensitivity in non-diabetic and diabetic individuals. Their paper also points out that prebiotic dietary fiber may enhance immune function and that the benefits of fiber may be similar for both children and adults. They recommend that dietary fiber intakes for children and adults are 14 g/1000 kcal and point out that more research is needed. While this is a useful
8 Dr. David Williams Alternatives May 2012, page 5 9 Health benefits of dietary fiber. Anderson JW, Baird P, Davis RH Jr, Ferreri S, Knudtson M, Koraym A, Waters V, Williams CL. Source Department of Internal Medicine and Nutritional Sciences Program, University of Kentucky, Lexington, Kentucky. PMID: 19335713 [PubMed - indexed for MEDLINE]
figure for industrial food designers it is not very useful for someone attempting to eat a fiber rich diet from their refrigerator.
A more useful figure is provided by the United States National Academy of Sciences, Institute of Medicine who suggest that adults should consume 20–35 grams of dietary fiber per day, but the average American's daily intake of dietary fiber is only 12–18 grams.10
The ADA recommends a minimum of 20–35 g/day for a healthy adult depending on calorie intake (e.g., a 2000 Cal/8400 kJ diet should include 25 g of fiber per day). The ADA's recommendation for children is that intake should equal age in years plus 5 g/day (e.g., a 4 year old should consume 9 g/day). No guidelines have yet been established for the elderly or very ill.
The British Nutrition Foundation has recommended a minimum fiber intake of 18 g/day for healthy adults.
Table of suggested Dietary Fiber expressed in grams per day
18 g/day 18 g/day
20-35 g/day 20-35 g/day
Nat. Acad. of Sci.
20-35 g/day 20-35 g/day
38 g/day 25 g/day
30 g/day 21 g/day
These figures are the suggested minimum values of grams per day of dietary fiber someone should eat to obtain benefits. Will there be more benefits with more fiber? Will eating too much fiber harm? There is very little information to answer these questions and therefor they are unanswered. My best guess is that eating more will not be harmful as long as it is kept within reason and is used in an acceptable form. It appears that the minimum amount of fiber to gain health benefits is somewhere between 18 and 38 grams of dietary fiber per day for healthy adults. For the sake of argument I will accept 35 grams per day for adults as the minimum daily intake of dietary fiber to provide benefits.
How much food do you have to eat to consume 35 grams per day of fiber? The Mayo Clinic has a guide to answer this question at http://www.mayoclinic.com/health/high-fiber-foods/NU00582. An extract of some of the more common foods are:
Quantity of Food Needed to Obtain 35 Grams/Day of Dietary Fiber Mayo Clinic Supplied Value 35 grams / number of grams rounded up
Raspberries 1 cup is 8.0 grams Apple with skin 1 medium is 5.5 grams Orange 1 medium is 3.1 grams Rye Bread 1 slice is 1.9 grams Brown Rice, cooked is 3.5 grams/cup Split peas cooked 1 cup is 16.3 grams Boiled Broccoli 1 cup is 5.1 grams
You would need to eat 4.4 cups You would need to eat 6.36 apples You would need to eat 11.29 oranges You would need to eat 18.42 slices of rye bread You would need to eat 10 cups of brown rice You would need to eat 2.14 cups of split peas You would need to eat 6.86 cups
10 Linus Pauling Institute at Oregon State University, http://en.wikipedia.org/wiki/Dietary_fiber Page4 of5
Since fiber appears to hold significant value for health it should increase life expectancy. There is in fact a study completed by the US National Institute of Health and the American Association of Retired People (NIH-AARP) that I quote, “We found that dietary fiber intake was significantly inversely associated with risk of total death in both men and women.”11 This means that eating more fiber may increase your life expectancy!
Is there anything wrong with dietary fiber? Unfortunately there is no free lunch. Everything has a benefit tradeoff and dietary fiber is no exception. Dietary fiber may slow down the transit time of prescription drugs causing unexpected serum levels of the drug. This has been observed with opioids but is easy to manage by a trained medical professional.12 In addition mixing dietary fiber with opioids drugs may cause severe constipation or even an obstruction requiring medical intervention. Fiber may also bind to and expel some minerals which could be a problem for people with nutritional deficiencies but these are rare in developed nations. Finally, there is always the embarrassment of flatulence which is always present when bacteria are active in the gut. Since dietary fiber is food for the good bacteria there may be increased flatulence, however some people report a reduction in the amount of flatulence with continued use of dietary fiber.
There may be one other thing wrong with dietary fiber and that is the food industry has started to call some man-made chemicals and products of bacteria and yeast that would have never been called dietary fiber, “functional” fiber.13 In addition the US Food and Drug Administration decided in 2007 that the chemical polydextrose can legally be called fiber. This chemical is already being used in children’s foods as fiber. The problem is that no one knows if these artificial dietary fibers have any of helpful properties of natural fiber but can legally claim to be fiber.14
One other consideration is that not all soluble fibers have the same actions. For example, Inulin from chicory root is considered a prebiotic which promotes symbiotic bacterial but doesn’t lower cholesterol. These problems can be resolved by using a blend of many different dietary fibers. In my opinion these appear to be good tradeoffs. Increased health in exchange for a little embarrassment! *Please seek assistance from a trained medical doctor prior to use if you have any medical condition. This paper is intended for educational purposes only.
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11 Dietary Fiber Intake and Mortality in the NIH-AARP Diet and Health Study, Yikyung Park, ScD; Amy F. Subar, PhD; Albert Hollenbeck, PhD; Arthur Schatzkin, MD Arch Intern Med. 2011;171(12):1061-1068. doi:10.1001/archinternmed.2011.18 http://archinte.jamanetwork.com/article.aspx?articleid=227566 12 An MD will know how much time delay is needed between ingestion of drugs and dietary fiber, if any.
13 Rodale Men’s Health November 2009 Page 102 14 Rodale Men’s Health November 2009 Page 104
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