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Fantastic Fibers: The Health Benefits of
Fiber in the Diet

"It's the healthiest gift you can give your body," was my grandmother's breakfast message about the oatmeal she served me 50 years ago.

She would be amused to know that the last 10 years of medical science have given proof to her intuition about the value of whole oats. Grandma would also chuckle that I am still following her breakfast advice with added ingredients like fresh or frozen berries.

Oatmeal and berries have a health value in common; they are not only nutritious in multiple ways but are also related as great fiber sources with important health benefits now recognized by the US Food and Drug Administration, Health Canada and European Medicines Evaluation Authority.

The FDA lists whole oats, barley and psyllium seed husk as excellent sources of dietary fiber that can reduce cancer risk via regular dietary intake.

Health Benefits of Fiber in the Diet

Consumed as long as people have eaten plants, dietary fiber has recently come into the view of governments, nutrition advisory groups and the public as one of our most important dietary macronutrients.

However, nutritionists have estimated that Canadians and Americans consume less than 50% of the required daily fiber amount to maintain intestinal health and its multiple other benefits.

Consistent intake of fiber through foods like whole grains, berries and other fresh fruit, vegetables, seeds and nuts is now associated with reduced risk of some of the world's most prevalent diseases including:

* Several types of cancer

* Obesity

* Type 2 diabetes

* High blood cholesterol

* Cardiovascular disease

* Numerous gastrointestinal disorders (constipation, inflammatory bowel disease, ulcerative colitis, Crohn's disease, diverticulitis and colon cancer)

Fiber Health Benefits

Recent medical research has proven several physiological benefits of consuming fiber, among which are:

* Improved absorption of calcium, magnesium, and iron

* Reduction of blood cholesterol and triglyceride levels

* Stabilization of blood glucose levels after a meal, i.e., a low glycemic index food source

* Maintenance of an optimal intestinal environment

* Stimulation of immune responses

Over the past 30 years, government agencies around the world have undertaken analyses and definitions of fiber to more accurately describe this dietary nutrient. Among some 32 reports filed, the most universally accepted definition is one by the American Association of Cereal Chemists. The AACC focused on the physiological and metabolic significance of fiber, defining it as:

"…[T]he edible parts of plants or similar carbohydrates resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine."

Recognizing these facts, advisories now exist in several countries for increasing adult intake of dietary fiber to 30 grams per day, double the current intake levels. Achieving this goal has been difficult because high-fiber foods do not always taste good and may lack other qualities needed to attract consumers.

Resistant Starch and Fermentation Provide Health Benefits

Let's review some properties of how our bodies use fiber. "Resistant starch" (same as "resistant carbohydrates") is a term sometimes used to refer to fiber sources resistant to complete digestion in the small intestine. These fiber sources need to pass through to the large intestine perhaps only attracting water along the way. In the large intestine they undergo fermentation by the colonic bacteria.

We should remember that fermentation of fiber is normal and healthy, even if fiber products sometimes cause minor gastric discomfort when the user has not previously had sufficient fiber in their diet.

"Fermentation" is one normal biological process many people never consider when they eat healthy foods like fresh berries or vegetables. Fermentation simply is the breakdown of soluble, resistant starch comprised mainly of carbohydrate molecules in the large intestine, yielding gases and further useful chemicals like short-chain fatty acids. A typical property of soluble fibers is to bind water forming a viscous gel having numerous health benefits during passage through the digestive system.

Other dietary fiber sources include polysaccharides (starch or sugar chains of dozens to many hundreds or thousands of units), oligosaccharides (short-chain sugars, usually 2-20 units long), monosaccharides, lignins and "insoluble" fiber sources such as cellulose, plant waxes and collagens. Insoluble fiber sources, however, do not undergo fermentation, but are nevertheless valuable for their water-attracting properties that aid bowel regularity.

Some of the soluble fiber sources you may see in public news and a variety of functional foods are:

* Pectins, a seed-like component common in berries, fruits, legumes

* Cellulose from brans and many vegetables

* Beta-glucans in whole oats and barley

* Plant waxes from many edible species

* Polyfructoses from inulin and oligofructans

* Gums and mucillages from tree exudates, fermentation of corn syrup (xanthan gum), algae (agar, carageenan) and grain seeds (e.g., psyllium seed husk)

Should fiber be new to your diet, add sources of fiber to your diet gradually over a month. This will allow your intestinal system to adjust slowly until the 30 grams per day of fiber become your normal intake. Drink plenty of water. If you have persistent discomfort from using fiber sources, speak with your doctor or a nutritionist.

Fiber Fermentation and Prebiotic Nutrient Value

The process of intestinal fermentation involves action by natural bacteria, sometimes called flora, residing in our large intestine (primarily the colon). These bacteria require soluble fiber as fuel and as sources for fermentation to produce valuable chemicals and health benefits.

Since the fiber serves as food for the bacteria already in the intestine, this is called a "prebiotic" nutrient value, meaning that before the bacteria can serve their main purpose in digestion — producing enzymes that digest food — they must be fed with a substrate they prefer (i.e. fermentable fibers). The main intestinal flora are bifidobacteria and lactobacilli that are essential for our health.

Berry pectins, inulin, psyllium and xanthan gum, all mentioned in the above list, are sources of soluble fibers that provide this prebiotic function in the normal fermentation process.

The Rubus berries such as the blackberry (Rubus nigra) and red raspberry (Rubus idaeus) have the highest density of dietary fiber per gram than any other published food source.

Fermentation is a metabolic process involving the use of one organic source to create others, such as enzymes to digest food that then release new elements. Among products of fermentation are gases (methane, carbon dioxide, hydrogen, nitrogen) and short-chain fatty acids, which result as new molecules clipped from the more complex digested fiber and food compounds.

Short-chain fatty acids such as butyric acid, acetic acid, propionic acid and valeric acid make up about 90% of the total fatty acid yield from fermentation in the human body. Collectively, these fatty acids have several beneficial physiological effects in the large intestine worth repeating from above.

Fatty acids…

* Enhance absorption of calcium, magnesium and iron (thus are important to bone and blood health)

* Contribute to lowering blood cholesterol and triglyceride levels

* Promote colon health by raising acidity levels that improve nutrient absorption and lower risk of colon cancer

* Act as anti-inflammatory mediators

* Stimulate immune protection through an array of intermediate effects within the intestinal system, including cytokine production

* Appear to inhibit appetite, leading to reduced calorie intake and weight gain

Insoluble fiber sources from plants, such as cellulose, typically undergo no fermentation so do not contribute new elements. Rather, they bind water effectively, making them valuable in digestion as stool softening agents with the essential benefit of promoting bowel regularity.


Including more fiber in your diet is a crucial step towards a healthier lifestyle. From oatmeal to berries the combination of ways to creatively include this nutrient are countless. Why wait?

About The Author:
Dr. Paul Gross is a scientist and expert on cardiovascular and brain physiology. A published researcher, Gross recently completed a book on the Chinese wolfberry and has begun another on antioxidant berries. Gross is founder of Berry Health Inc, a developer of nutritional, berry-based supplements. For more information, visit http://www.berrywiseonline.com.

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