Module 3.3
Photosynthesis &
Fiber
By Jennifer Turley and Joan Thompson
© 2013 Cengage
Presentation Overview
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6.
Photosynthesis
Carbohydrate structures: sugar, starch, fiber
Fiber categories & recommendations
Fiber benefits & actions
Negative effects of too much fiber
Food sources
Photosynthesis
 Process
by which plants make carbohydrate
structures
 Photosynthesis
 CO2
requires chlorophyll
+ H20 + sunlight 
carbohydrate in plants
•
•
•
sugars
starch
fiber
Fiber Content in Food
 Dietary
fiber- The residue after “in vivo” treatment.
Animal tested
 Functional
Fiber- Indigestible carbohydrate isolated
from natural sources or synthetic indigestible
carbohydrate.
•
•
Has beneficial physiological effects in humans
An example of indigestible carbohydrate isolated
from a natural source is cellulose gel added to a
processed food
Fiber Content in Food
 Total


Fiber-
The combination of dietary & functional fiber
Is reflected as the fiber content value on food
package labels in the Nutrient Facts Panel
Categories of Fiber
 Soluble:
Solubility Fiber
Sources
Food
Sources
Softens &
Pectins
Gels in
Gums
water. Does Mucilages
attract
water
Fruits (like
apple
pectin),
vegetable,
legumes,
and oats
Categories of Fiber
 Insoluble:
Solubility
Fiber
Sources
Does not
Cellulose Hemisoften or gel in cellulose
water. Does
Lignins
attract water
Food
Sources
Whole grain
foods,
Celery strings
Apple peels
Fiber Recommendations
 DRI


for total fiber intake:
Adult males= 38g
Adult females= 25g
 Personalized
consumed
 Example:
DRI is 1.4g total fiber per 100 Calories
a person eating 4200 Calories/ day
should consume 59g of fiber
High Fiber Intake & Food Sources
 High
fiber intake is well above
2g/ 100 Calories consumed
 High
fiber foods provide >2g fiber
per serving
 How
you assess high fiber:
 Compare
total grams of fiber to total
Calories per serving
Fiber Food Sources
 Grains
 Cereals
 Legumes
 Fruits
& Vegetables
 Most
American’s under consume these types of
foods, and thus fiber.
 Average
American intake is 11-13g fiber/ day
Fiber in Foods
Food Sources
Food
Very High
High
Good
Low
Group
>4gm
2-4gm
1-2gm
≤1gm
½ C Bran
Flakes
1 C Shredded
whole wheat
or whole
multigrain
cereal
1C
Oatmeal or
puffed
brown rice
cereal
1 Slice
Whole
Wheat
Bread
1 Slice Rye
Bread
½ C Brown
or Wild Rice
1 Corn
Tortilla
1C
Cornflakes
½ C White
Rice
½ C Pasta
Grains
Food Sources
Food
Group
Very
High
High
Good
Low
2-4gm
1-2gm
<1gm
½C
Broccoli,
Cauliflower,
Corn,
Beans,
Cabbage
1oz Nuts &
Seeds
½C
Carrots,
Green
pepper,
Celery,
Onion,
Lettuce
1 C Some
Vegetable
Juices
>4gm
Vegetable
½C
Legumes
(dried
beans)
Food Sources
Food
Very High High
Good
Low
Group
>4gm
2-4gm
1-2gm
<1gm
N/A
1 Apple,
Banana
Orange,
Peach,
1 C Berries
2 Prunes
½C
1 C Fruit
Watermelon Juice
Honeydew
melon,
Cantaloupe
Fruit
Benefits/ Actions of Fiber:
Bulk
 Increases
the volume of food in the diet without
adding calories… decreases caloric density of food
 Bulks
the volume of stool
 BOTH
soluble & insoluble fiber provide bulk
Benefits/ Actions of Fiber:
Stool Softener
 Complex
carbohydrate chemical structures are
hydrophillic (i.e. water-loving)  binds/attracts
water  creating a softer stool that is easier to
move along the G.I. tract.
 Relieves
constipation, hemorrhoids & diverticulosis
Benefits/ Actions of Fiber:
Stool Softener
 Complex
carbohydrate chemical structures are
hydrophillic (i.e. water-loving)  binds/attracts
water  creating a softer stool that is easier to
move along the G.I. tract.
 Relieves
 BOTH
constipation, hemorrhoids & diverticulosis
soluble & insoluble fiber act as a softener
Benefits/ Actions of Fiber:
Decreases transit time
 Food,
the bolus, chyme and feces move through
the GI tract faster  thus the transit time is reduced
 Decreases
time in the colon
 Reduces
exposure time to potential carcinogens
thus reduces colon cancer
 BOTH
soluble & insoluble fiber provide these
benefits
Benefits/ Actions of Fiber:
Improves GI tract muscle tone
 The
larger volume of bulk and the softer mass
moving through the “tube” allows the GI tract
muscles to exercise efficiently
 BOTH
soluble & insoluble fiber provide this benefit
Benefits/ Actions of Fiber:
Heart Health
 Reduces
heart disease risk by binding cholesterolrich bile in the GI tract
 Normally,
bile is reabsorbed
 Bile
binds tightly to soluble fiber & cannot be
reabsorbed
 Thus,
a large source of cholesterol can be excreted
in the feces
 ONLY
Soluble fiber provides this benefit
Benefits/ Actions of Fiber:
 Bile
binds tightly to soluble fiber & cannot be
reabsorbed
Benefits/ Actions of Fiber:
Slows gastric emptying time
 It
takes a longer time for the chyme to leave the
stomach
 The
rate of glucose absorption is slowed
 This
is beneficial with diabetes & reactive
hypoglycemia
 ONLY
soluble fiber provides this benefit
Benefits/ Actions of Fiber:
 This
is beneficial with diabetes & reactive
hypoglycemia
Too Much Fiber: Negative Effects

Causes gas & bloating (due to decomposition of fiber
by gastrointestinal microbes)

Too large & frequent bowel movements

Binds positively charged minerals

Binds beta-carotene

Decreases caloric value

Can cause GI tract blockages without adequate water
intake

Too much soluble OR insoluble fiber can cause negative
effects
Whole Grain Processing
 Refined
germ
wheat kernels  removes the husk, bran &
 The
endosperm (containing mostly starch & protein)
remains
 Iron,
thiamin, riboflavin, niacin, folate, vitamin B6,
magnesium, zinc, & fiber are lost
Whole Grain Processing
 Some
nutrients are added back into refined grain
products as a result of the Enrichment Act of 1942
 Enriched-nutrients
 Fortified-nutrients
that were lost are added back in
that are not
naturally occurring in that food are
added in
% Nutrients in whole grain, enriched white & un-enriched white breads
Summary
 Plants
 Fiber
make carbohydrates via photosynthesis
is non-caloric
 Categories
 Total
 The
are soluble & insoluble
fiber = functional & dietary fiber
DRI is 1.4 gm/100 Calories eaten
 There
are health benefits for adequate
fiber intake
 There
are negative effects from too much fiber
 Whole
foods provide the best source of fiber and
nutrients.
References for this presentation are the same as those for this topic found in module 3 of the textbook