Photosynthesis and Fiber

By Jennifer Turley and Joan Thompson

© 2016 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, Part 1

• Dietary Fiber: The residue after “in vivo” treatment. Animal tested.

Fiber Content in Foods, Part 2• 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, Part 3• 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 & Gels in water. Does attract water

Pectins

Gums

Mucilages

Fruits (like apple pectin), vegetable, legumes, and oats

Categories of Fiber:Insoluble

Solubility Fiber Sources Food Sources

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 male is 38 grams. Adult female 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

Grains

Cereals

Legumes

Fruits

Vegetables

Most Americans under consume these types of foods and thus fiber. The average American’s fiber intake is 11-13 gm/day.

Fiber in Foods

Food Sources & Amounts of Fiber, Part 1

Food

Group

Very High

>4gm

High

2-4gm

Good

1-2gm

Low

≤1gm

Grains ½ C Bran Flakes

1 C Shredded whole wheat or whole multigrain cereal

1 C Oatmeal or puffed brown rice cereal

1 Slice Whole Wheat Bread

1 Slice Rye Bread

½ C Brown or Wild Rice

1 Corn Tortilla

1 C Cornflakes

½ C White Rice

½ C Pasta

Food Sources & Amounts of Fiber, Part 2

Food

Group

Very High

>4gm

High

2-4gm

Good

1-2gm

Low

<1gm

Vegetable ½ C Legumes (dried beans)

½ C Broccoli, Cauliflower, Corn, Beans, Cabbage

1oz Nuts & Seeds

½ C Carrots, Green pepper, Celery, Onion, Lettuce

1 C Some Vegetable Juices

Food Sources & Amounts of Fiber, Part 3

Food

Group

Very High

>4gm

High

2-4gm

Good

1-2gm

Fruit N/A 1 Apple, Banana

Orange, Peach,

1 C Berries

2 Prunes

½ C Watermelon,

Honeydew melon,

Cantaloupe

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, Part 1

• Reduces heart disease risk by binding cholesterol-rich bile in the GI tract.

• Normally, bile is reabsorbed.• Bile binds tightly to soluble fiber &

cannot be reabsorb.• Thus, a large source of

cholesterol can be excreted in the feces.

• Soluble fiber provides this benefit.

Benefits-Actions of Fiber: Heart-Health, Part 2

Benefits-Actions of Fiber: Increases 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.

• Soluble fiber provides this 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, Part 1

• 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, Part 2

• 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

Husk,

Bran &

Germ are

removed

% Nutrients in whole grain, enriched white & unenriched white breads

whole grain is best

Some Summary Points• 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