2010 lecture 3 digestive system

7/31/2019 2010 Lecture 3 Digestive System

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Why Do We Eat?

Food provides us with

Energy for body processes

Heat for body temperature regulation

Building blocks for growth and maintenance ofbody tissues


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Constant turnover of substancesRequire energy to continue to function

Require nutrients


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What Happens to the Food We Eat?

The food we eat undergoes three processes:1. Digestion

2. Absorption

3. Elimination

These processes occur in the gastrointestinal

tract.our food processor!


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What Happens to the Food We Eat?


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Digestion

Digestion: the process of breaking large foodmolecules down to smaller molecules.

Digestion includes: Mechanical digestion: the physical breakdown

of food.

Chemical digestion: enzymatic reactions thatbreak down large food molecules.


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Digestion: Chewing


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Digestion: Swallowing


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Digestion: Swallowing


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Digestion: The Stomach


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Rate of Stomach Emptying

2-6 hrs depending upon composition of meal High CHO contentfastest

High proteinfast

High fatslowest release of hormones that slow GI motility

*Think about the composition of your breakfast...how

hungry are you by lunch time?


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Why does your stomach growl?

Gas in the stomach mixing with food or fluids.

Growling tends to be louder when your stomach

is empty as there is no food to muffle the noise!


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Digestion: Accessory Organs


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Digestion is complete when CHOs, proteins &fats are reduced to substances that can be

absorbed & when vitamins & minerals are

released from food.


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Absorption

Absorption: the process of taking moleculesacross a cell membrane and into cells of the body.

Nutrients are taken up by the lymph (fats) &circulatory (CHO & protein) systems for

distribution to body cells for use or storage.

99% of CHO, 92% of protein & 95% of fat that

we consume is digested & absorbed


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Absorption


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Elimination


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Elimination

Undigested food components move through asphincter called the illeocecal valve to the large

intestines.

In the large intestine:

Very little digestion takes place

Material is stored 12-24 hours prior toelimination

Water and some nutrients are absorbed


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Elimination

MicrofloraSynthesize small amts of fatty acids, some B vitamins& vitamin K

By product of bacterial metabolism is gas (200 to2000mL per day!)

Feces

Undigested matter, dead cells, secretions from the GItract, water and bacteria


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Should you feed your flora?! Probiotic therapy

300-500 different species!

# of bacteria living in your gut is 10X greaterthan the total # of cells in your entire body!

Breakdown indigestible substances, synthesizevitamins, metabolize harmful substances and

help with intestinal immune function


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Probiotic therapy

Ingestion of good or healthy bacteria

Improve digestion of lactose in lactose-intolerant people

Prevent diarrhea associated with antibiotic use orintestinal infections

Reduce the production of toxic substances in the colon

Inhibit the activity of enzymes that produce carcinogens


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Disadvantages

Once they are no longer consumed, probiotics wash outof the system quite quickly

Growth of healthy bacteria can be promoted byconsuming prebiotics

-currently sold as supplements

-also in tube feeding formulas

Risk of using probiotics or prebiotics are considered

negligible


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Disorders Related to Digestion

Excluding childbirth, digestive disorders(heartburn, hemorrhoids, IBS & ulcers) are the

leading cause of hospitalization among Canadian

adults aged 20-44 years!


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Constipation Myths!

1. Poisonous substances are absorbed fromstools & cause autointoxication disease

2. Extra long colons cause constipation

3. All cases of constipation are caused byinadequate fiber intake

4. You can treat it by drinking plenty of fluid

5. You can lose weight & stay healthy if youtake laxatives regularly

6. If you do not have a bowel movementeveryday there is something wrong with you


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Peptic ulcers are regions of the GI tract that havebeen eroded by HCL and pepsin.

Duodenal ulcers are 10X more common thanstomach ulcers

The bacteriumHelicobacter pylori contributes tothe production of both stomach and duodenal

ulcers.

Ul


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Ulcers


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Antacids

Can be an overlooked source of nutrientscheck the label!!

Alka-seltzer Na+ & HCO3- (1 tablet has 24% of DV for Na +)

Some antacids contain aluminum limits phosphorus absorption &causes constipation

Some contain Ca++ & magnesium hydroxide

something that many diets are low in so the amts in the tabletscould be an ok supplement

higher doses of magnesium cause diarrhea!

Many also contain sugar (taste) and starch (filler)


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Celiac disease Complete intolerance for gluten, a protein

found in wheat, rye, barley.

Can damage the small intestine leading to poorabsorption of nutrients.

Requires a diet lacking wheat, rye, barley.

There may be a genetic component to thedisease.

I it bl B l S d


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Irritable Bowel Syndrome

-affects 10-15% of the populationSymptoms

Cramps, bloating, increased frequency, diarrhea,constipation

Causes Altered intestinal peristalsis Decrease pain threshold

Individualized treatment

Moderate caffeine Low-fat, small, frequent meals

Stress reduction


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Diarrhea Can be caused by food intolerances, infection

of the GI tract, stress, bowel disorders or

deficiencies of Vit A, zinc or other nutrients

Can lead to severe dehydration

Is more dangerous for children and the elderly

Resting the Gut nada! Once rehydrated,

should eat solid foods such as yogurt, potatoes,

chicken, rice cereals etc. to provid nutrients to

repair the intestinal tract.


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Gallstones

Major cause of illness and surgery

Solid material in the gallbladderprimarily cholesterol

Excess body weight a risk. especially in women.

Lead to pain in the upper abdomen and bloating

Surgical removal of the gallbladder most common

Prevention of gallstones: avoid overweight, limit animalprotein, high fiber diet, regular physical activity


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Lactose Maldigestion & Intolerance

Lactose found in milk & milk products presents aproblem for most of the worlds adults

Occurs more commonly in populations that have

no historical links to dairy farming & milkdrinking

Asian Americans 90%

Africans & African Americans 70%Asian s 65% or more


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Production of lactase is genetically determined some adults produce little or no lactase &

can consume very little milk product

some adults produce some lactase & cantolerate limited amounts of milk products

**Lactase tablets can help a bit but benefit islimited due to inactivation of lactase by digestive

processes in the stomach


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So why doesnt the yogurt bother me?

Many lactose-intolerant people can consumefermented milk products (aged cheese,

buttermilk)

The bacteria used to culture the product candigest or more of the lactose


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If you have lactose maldigestion

Should NOT eliminate milk & milk productsfrom the diet

Fortified soy milk

Low-lactose cows milkYogurt

Parmesan cheese

Aged cheeseKefir

2010 lecture 3 digestive system

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