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Photosynthesis and Fiber
By Jennifer Turley and Joan ThompsonBy Jennifer Turley and Joan Thompson
© 2013 Cengage© 2013 Cengage
Presentation Overview
• Photosynthesis• Carbohydrate structures: sugar,
starch, fiber• Fiber categories & recommends• Fiber benefits & actions• Negative effects of too much
fiber• Food sources
Photosynthesis
• The process by which plants make carbohydrate structures.
• Photosynthesis requires chlorophyll.
• CO2 + H20 + sunlight = carbohydrate in plants.• sugars• starch • fiber
Fiber Content in Foods
• Dietary Fiber: The residue after “in vivo” treatment. Animal tested.
Fiber Content in Foods• 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 Foods
• Total Fiber: • Is the combination of dietary &
functional fiber in food.
• Is reflected as the fiber content value on food package labels in the Nutrition Facts panel.
Categories of Fiber:Soluble
Solubility Fiber Sources
Food Sources
Softens & Softens & Gels in Gels in water. Does water. Does attract attract waterwater
PectinsPectins
GumsGums
MucilagesMucilages
Fruits (like Fruits (like apple apple pectin), pectin), vegetable, vegetable, legumes, legumes, and oatsand oats
Categories of Fiber:Insoluble
SolubilitySolubility Fiber Fiber SourcesSources
Food Food SourcesSources
Does not soften or gel in water. Does attract water
Cellulose Hemi-cellulose
Lignins
Whole grain foods,
Celery strings
Apple peels
Fiber Recommendations
• The DRI for total fiber intake:• Adult ♂ is 38 grams. Adult ♀ is 25 grams.
• Personalized DRI is 1.4 grams total fiber per 100 Calories consumed.
• Example: A person eating 4200 Calories in 1 day should consume 59 grams of fiber.
High Fiber Intake & Foods
• High fiber intake is well over 2 grams/100 Calories consumed.
• High fiber foods provide > 2 gm fiber/serving.• High fiber foods are easy to assess on the food
package label by comparing the grams of fiber with reference to the Calories provided/serving.
Fiber Food Sources
Most American under consume these types of foods and thus fiber. The average American fiber intake is
11-13 gm/day.
Fiber in Foods
Food Sources & Amounts of Fiber
Food
Group
Very High
>4gm
High
2-4gm
Good
1-2gm Low
≤1gm
Grains
½ C Bran ½ C Bran FlakesFlakes
1 C Shredded 1 C Shredded whole wheat whole wheat or whole or whole multigrain multigrain cereal cereal
1 C 1 C Oatmeal or Oatmeal or puffed puffed brown rice brown rice cerealcereal
1 Slice 1 Slice Whole Whole Wheat Wheat Bread Bread
1 Slice Rye 1 Slice Rye BreadBread
½ C Brown ½ C Brown or Wild Riceor Wild Rice
1 Corn 1 Corn Tortilla Tortilla
1 C Cornflakes1 C Cornflakes
½ C White ½ C White RiceRice
½ C Pasta½ C Pasta
Food Sources & Amounts of Fiber
Food
Group
Very High
>4gm
High
2-4gm
Good
1-2gm Low
<1gm
Vegetable
½ C ½ C Legumes Legumes ((dried dried beans)beans)
½ C ½ C Broccoli, Broccoli, Cauliflower, Cauliflower, Corn, Corn, Beans, Beans, CabbageCabbage
1oz Nuts & 1oz Nuts & SeedsSeeds
½ C ½ C Carrots, Carrots, Green Green pepper, pepper, Celery, Celery, Onion, Onion, LettuceLettuce
1 C Some 1 C Some Vegetable Vegetable JuicesJuices
Food Sources & Amounts of Fiber
Food
Group
Very High
>4gm
High
2-4gm
Good
1-2gm Low
<1gm
Fruit
N/AN/A 1 Apple, 1 Apple, BananaBanana
Orange, Orange, Peach,Peach,
1 C Berries1 C Berries
2 Prunes2 Prunes
½ C ½ C Watermelon,Watermelon,Honeydew Honeydew melonmelon,,
CantaloupeCantaloupe
1 C Fruit 1 C Fruit JuiceJuice
Benefits-Actions of Fiber: Bulk
• Increases the volume of food in the diet without adding Calories, thus it decreases the caloric density of the food.
• Bulks the stool volume.
• Both soluble & insoluble fiber provide these benefits.
Benefits-Actions of Fiber: Stool Softener
• Complex carbohydrate chemical structures are hydrophillic (binds water or attracts water) creating a softer stool that is easier to move along the G.I. tract.
• Relieves constipation, hemorrhoids, & diverticulosis.
• Both soluble & insoluble fiber provide these benefits.
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 Reduces heart disease risk by binding cholesterol-rich bile in the binding cholesterol-rich bile in the GI tract.GI tract.
• Normally, bile is reabsorbed.Normally, bile is reabsorbed.• Bile binds tightly to soluble fiber & Bile binds tightly to soluble fiber &
cannot be reabsorb.cannot be reabsorb.• Thus, a large source of Thus, a large source of
cholesterol can be excreted in the cholesterol can be excreted in the feces.feces.
• Soluble fiber provides this benefit.Soluble fiber provides this benefit.
Benefits-Actions of Fiber:Heart-Health
In presence of soluble fiber is excreted
Liver Makes Bile from Cholesterol
Gallbladder stores Bile
Released Bile emulsifies fat in G.I. tract
In absence of soluble fiberBile is reabsorbed, little is excreted
Bile is reabsorbed
Benefits-Actions of Fiber: Increases gastric emptying time.
• It takes a longer time for the It takes a longer time for the chyme to leave the stomach.chyme to leave the stomach.
• The rate of glucose absorption is The rate of glucose absorption is slowed.slowed.
• This is beneficial with diabetes & This is beneficial with diabetes & reactive hypoglycemia.reactive hypoglycemia.
• Soluble fiber provides this Soluble fiber provides this benefit.benefit.
Negative Effects of too Much Fiber
• 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
• Wheat kernels are refined by removing the husk, bran, & germ.
• 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.• Added: iron, thiamin, riboflavin, niacin, folate
• Not Added: vitamin B6, magnesium, zinc, fiber
Processing a Wheat Kernel
% Nutrients in whole grain, enriched white & unenriched white breads
Fiber Summary• Plants make carbohydrates via
photosynthesis.• Fiber is non-caloric.• Categories are soluble & insoluble.• Total fiber = functional & dietary fiber.• The 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