According to Wikipedia dietary fiber is “is the indigestible portion of plant foods”.

Wait a minute, there!  If fiber is an indigestible material, why is it such an important part of the human diet?

Excellent question.  On a basic level, fiber is what helps things move.  We all know that after we eat food, it must pass through our digestive system and then, um, leave.  Without fiber, this process is very difficult.  (Dietary fiber has many other benefits, continue reading to find out more.)

Some Minor Details

There are two basics kinds of dietary fiber:  soluble fiber and insoluble fiber.  Soluble fiber absorbs water in the intestine and forms a gummy substance; it also is easily fermented by intestinal bacteria.  Soluble fiber benefits the body in two significant ways:  it lowers cholesterol and lowers our bodies’ reaction to sugars.  The liver uses cholesterol to produce bile acids, which aid in the digestion of fats in the intestines.  Soluble fiber binds to bile acids, essentially pulling them along for the ride out of the intestinal tract.  In this way, soluble fiber aids the body in lowering cholesterol levels.  Soluble fiber works similarly with sugars.  Sugar molecules (which are relatively bulky) are trapped in the gummy substance the soluble fiber forms in the intestines, disabling it from absorbing into the intestinal walls quickly.  When sugar absorbs slowly into the intestinal walls, you don’t get a “sugar rush”, the telltale sharp increase in energy and sudden drop of energy associate with the consumption of simple sugars.  (Quick digestive tract review:  there are millions of capillaries along the intestinal walls which absorb the nutrients that your food is broken down into, these nutrients travel through your blood stream to muscles and major organs.)

Some sources of soluble fiber include:

oats

beans

peas

citrus

apricots

bananas

apples

broccoli

carrots

sweet potatoes

onions

flax seeds

almonds

and more.

 

Insoluble fiber is “metabolically inert”, which means it does not bind to any nutrient or molecule in the intestines.  It simply absorbs water, increases in volume, and eases bowel movements.  Though soluble fiber has some surprising health benefits, insoluble fiber simply increases bowel volume, softens stools, and decreases the time waste stays in the intestinal tract.  Simply put, insoluble help prevent constipation.

Good sources of insoluble fiber include:

whole grains

wheat

bran

seeds

potato skins

green beans

zucchini

avocado

kiwi skins

tomato skins

and more.

The big question left is how much fiber do I need?  General guidelines state that women should eat about 25 g of fiber per day, while men should eat about 38 grams of fiber per day.  Children require less fiber than adults because they have smaller intestinal tracts.  Women need different amounts of fiber during different times of their lives, but I’ll discuss that later in the week.

For now I’ll leave you with some of my resources:

http://www.healthcalculators.org/calculators/fiber.asp?Submit=Close – University of Maryland calculator for daily fiber intake based on age, sex, and body build

http://en.wikipedia.org/wiki/Dietary_fiber#Fiber_recommendations_in_the_USA – the good old wiki

http://www.ext.colostate.edu/pubs/foodnut/09333.html – Colorado State article on the benefits of fiber

Next Up:  Fats Won’t Make You Fat

 

 

 

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