Berries, a Great Source of

Dietary Fiber

Part 2 of 3  

Berry Fibers

Give Health Benefits

Following Intestinal Fermentation

 
                                                                                     
                                                                                                                 Elderberries (Sambucus nigra)                    

 ** [NOTE: for additional background and published literature, see Wikipedia links with this color] **

Summary from Part 1 (click)

Highly beneficial for human health,

  fermentation of prebiotic fibers occurs naturally in the colon of

the lower digestive tract, within the mid- and lower large intestine.

Click here for a good review of the human digestive tract and its functions

 

Why is fiber good for us?

Most people associate fiber with bowel regularity - a valuable benefit in itself -

but this is only a minor part of the fiber story.

"Soluble" fibers, also called fermentable or viscous fibers, have

a wider range of health benefits than do insoluble fibers.

3 species of Rubus berries: blackberries, red raspberries and salmonberries (British Columbia)

Among the richest sources of soluble fibers in the berry category

Courtesy of Berry Wise

The Berry Fiber Story: Plain and Simple

  • Berries generally -- but açaí, Rubus and wolfberries (goji) especially --

have exceptional fiber content (>10% of fruit weight)

  • Most berries have relatively thin skins, so are not

especially important as sources of insoluble fiber

  • Content of soluble (fermentable) fibers in berries, however, is high,

due to pectins, hemicelluloses, and polysaccharides (click for Wikipedia definitions),

among the densest of plant food sources of these mixed fermentable fibers

 

What Happens When Berry Fibers Ferment?

The normal, healthy process of fermentation in the colon involves action by our natural bacteria, sometimes called flora, residing throughout the large intestine. These bacteria require soluble fiber as fuel for their own energy uses, and as sources for fermentation to produce valuable byproducts with distinct health benefits described below and in Part 3.

Since the fiber serves as food for the bacteria already in the colon, this is called a “prebiotic” nutrient value, meaning that before the bacteria can serve their main purpose in digestion -- producing enzymes that extract all the nutrients from food -- they must be fed with a substrate they prefer (i.e. fermentable fibers). The main intestinal flora are bifidobacteria and lactobacilli, often identified on the labels of retail yogurts, that are essential for our intestinal health.

A health effect at work:

Bifidobacteria and lactobacilli increase their numbers, have enhanced

enzymatic functions, and produce greater amounts of short-chain fatty acids (below) when fed soluble fibers they can ferment!

 

Berries are sources of soluble, fermentable fibers that provide

this health-promoting prebiotic function in the fermentation process.

Fermentation occurs by action of colonic bacteria on the food mass,

producing short-chain fatty acids from the fiber molecules. The fatty acids are called

butyric, acetic, propionic, and valeric acids --

with significant health properties.

** So, for those who thought fiber was only for maintaining regularity... **

 

Health effects of short-chain fatty acids:

  1. Enhance absorption of calcium, magnesium and iron (important for bone and blood health)
  2. Contribute to lowering blood cholesterol and triglyceride levels by inhibiting absorption of dietary saturated fats and signaling reduced production of cholesterol by the liver (important for cardiovascular health -- this is the claim allowed on labels of high-fiber foods by the US FDA, see Part 1)
  3. Act as food for cells lining the colon, called colonocytes, a critical immune interface for the body (important for immune health)
  4. Promote colon health by raising acidity levels that improve nutrient absorption
    and lower risk of colon cancer     (important for lowering cancer risk)
  5. Act as anti-inflammatory mediators (important for health of the colon)
  6. Stimulate immune protection through an array of intermediate effects within the intestinal system, including cytokine production (other immune defense benefits)
  7. Inhibit appetite, leading to reduced calorie intake (important for weight control)

 

Summarizing

  • having berries in the diet provides a great source of soluble, fermentable fibers
  • upon fermentation by bacteria in the healthy colon, fibers not only provide nutrition for and increased numbers of intestinal bacteria ("good" bacteria required for human health), but also yield short-chain fatty acids with numerous health effects of their own

 

Coming Up!

 

Part 3: Lowering disease risk by increasing dietary intake

of berries or other high-fiber foods -- a brief survey of published

research on this topic

 

Archives (click!)

 

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Dr. Paul
The Berry Doctor

Fiber Reference

The Linus Pauling Institute, Micronutrient Information Center, Oregon State University, Corvallis, has an excellent discussion of dietary fiber and food sources; click here