Lecture Presentation Outline
I. Life - a chemical process
v Instructor Resources: Unit 7 Nutrition Scoreboard transparency master; Unit 7 PowerPoint presentation on Multimedia Manager
A. The substances that make up the organs and tissues of your body are constantly changing.
B. Tissues are continually renewing themselves.
C. Raw materials needed for renewal are the nutrients consumed in foods.
D. 5% replacement
1. About 5% of the components of cells are renewed daily.
2. Taste cells are replaced every seven days.
3. Intestinal tract lining cells are replaced every one to three days.
4. Skin cells are replaced every month.
5. Red blood cells turn over every 120 days.
E. Maintenance functions require nutrients as raw material.
F. Nutrients are Available!
1. Components of food converted to “useful body parts” are nutrients.
II. Digestion and absorption are the two separate but related processes that make nutrients from food available for use by every cell in the body.
A. Digestive System
v Instructor Resources: transparency #21: The Digestive System; Activity 7-3: Digestive Anatomy (demonstration); Activity 7-8: Online Digestive Sites
1. 25 to 30 feet of muscular tube, and secretory organs.
2. Secreted juices break foods into absorbable pieces.
a. Carbohydrates to glucose and fructose, monosaccharides.
b. Proteins to amino acids.
c. Fats to fatty acids and glycerol.
d. Vitamins and minerals are just released during digestion.
B. Digestion
v Instructor Resources: Activity 7-2: Digestive Anatomy (class activity)
1. Digestion is accomplished by enzymes manufactured in the digestive system.
v Instructor Resources: Activity 7-4: Amylase Enzymatic Digestion; Activity 7-6: Enzyme Supplement Claims; Activity 7-7: Bromelin Enzymatic Digestion
a. Salivary glands, stomach, and pancreas secrete these enzymes.
b. Enzymes are complex protein substances that speed up reactions that break down food.
c. Enzymes are not changed by the chemical reactions they affect.
d. They are reusable.
e. Over one hundred different enzymes participate in the digestion of carbohydrates, proteins, and fat.
2. Digestion in the mouth
a. Chewing causes glands under the tongue to release saliva.
b. Saliva lubricates food so that it can be swallowed.
c. Saliva also contains salivary amylase and lipase.
1. Amylase breaks down carbohydrates.
2. Lipase breaks down fats.
3. Esophagus to the Stomach
a. Food is swallowed and passes through the esophagus to the stomach.
b. Muscles at each opening of the stomach act as valves to ensure that food is liquefied, mixed with digestive juices, and ready for the digestive processes of the small intestine before it moves on.
c. Solid foods stay for over an hour, liquids pass through in about 20 minutes.
4. Stomach to Small Intestine
a. Stomach ejects a few teaspoons of liquefied contents into the small intestine at a time, until empty.
b. The ejection stimulates muscles in the intestinal walls to contract and relax (peristalsis). These movements mix food as it is digested by enzymes.
v Instructor Resources: Activity 7-1: Peristalsis
5. Small Intestine to Large Intestine
a. Food containing high fiber and sufficient fluids cause the bulge of digesting food in the intestine to be larger.
b. Larger food bulges stimulate a higher level of intestinal muscle activity than smaller food bulges.
c. High-fiber meals pass through the digestive system faster than low-fiber meals.
C. Structure of intestines
v Instructor Resources: transparencies #22: The Small and Large Intestines & #24: Structure of Villi
1. Digestion and absorption of nutrients enhanced by villi lining the inside of the intestinal wall.
2. Available surface area of small intestine is about the size of a baseball infield, 675 square feet.
3. This tissue requires a high level of nutrients for maintenance.
4. Much of this need (50% in small intestine and 80% in large intestine) met by food that is being digested.
D. Small intestine absorption
1. Digestion complete when carbohydrates, proteins, and fats are reduced to smaller substances that can be absorbed, and when vitamins and minerals are released.
2. Most nutrients are absorbed in the small intestine.
3. Water, sodium, and some of the end products of bacterial digestion are absorbed from the large intestine.
E. Large intestine absorption
1. Large intestine is home to many bacteria that use undigested fiber and complex carbohydrates that are not digested by human digestive enzymes.
2. These bacteria excrete gas and fatty acids that can be absorbed in large intestine.
3. Substances in that cannot be absorbed collect in the large intestine and are excreted in the stool.
F. Absorption
1. In Absorption the end products of digestion are taken up by lymphatic and circulatory systems for distribution to cells of body.
v Instructor Resources: transparency #23: The Lymphatic and Circulatory Systems
2. Lymph and blood vessels infiltrate villi lining inside of intestines and transport nutrients to the lymphatic and circulatory systems.
a. Breakdown products of fat digestion are absorbed into lymph vessels, whereas carbohydrate and protein products enter the blood vessels.
1. Circulatory System
b. Arteries and veins infiltrate villi.
c. Arteries pick up nutrients
d. Veins take away wastes.
2. Lymphatic System
a. Vessels infiltrate villi.
b. Lymphatic fluid has substances to bind fat and carry it to blood stream.
c. Nutrient-rich contents of lymphatic system spill into bloodstream near heart.
b. Vessels from both systems merge into one.
c. Lymph and blood are sent to heart and then throughout body via circulatory system.
d. Circulatory system reaches every organ and tissue, supplying cells with nutrients absorbed from food.
G. Beyond Absorption
1. Cells use nutrients directly for energy, body structures, or the regulation of body processes, or convert them into other usable substances.
a. Glucose delivered to cells can be used “as is” for energy formation or converted to glycogen and stored for later use.
b. Fatty acids, an end product of fat digestion, can be incorporated into cell membranes or used in the synthesis of certain hormones.
c. Vitamins and minerals freed from food by digestion can be used by cells to control enzyme activity or can be stored for later use.
2. The body has a limited storage capacity for some vitamins and minerals.
3. Excessive amounts of certain vitamins and minerals such as vitamin C, thiamin, and sodium are largely excreted in urine.
H. Digestion and Absorption
1. Approximately 99% of carbohydrate, 92% of protein, and 95% of fat we consume are digested and absorbed.
2. Dietary fiber leaves digestive system in same form as it entered.
a. Humans have no enzymes to break down fiber.
b. Some fiber is digested in the large intestine by bacteria.
III. Digestive Disorders
· Digestive disorders such as heartburn, hemorrhoids, irritable bowel syndrome, and duodenal and stomach ulcers are leading cause of hospitalization among U.S. and Canadian adults aged 20-44 years.
· Account for over 70 million medical visits yearly in the U.S.
· Digestive disorders are common in children as well as adults.
· At least one-third of U.S. adults experience heartburn, and up to 28% of school children experience constipation.
A. Constipation and Hemorrhoids
1. Constipation and hemorrhoids are due to diets with too little fiber.
2. Adults need fiber intakes of 25 to 30 gm/day plus plenty of fluids.
3. This regimen will help prevent constipation and hemorrhoids in healthy people.
B. Ulcers
1. Ulcers develop when protective barrier lining stomach and duodenum is damaged.
2. Stomach acid and digestive enzymes erode lining of the stomach and duodenum and cause an “ulcer.”
3. Duodenal ulcers are more common than stomach ulcers, closely associated with Helicobacter pylori (H. pylori) bacteria.
v Instructor Resources: CNN Today Nutrition Vol. 3: Broccoli Benefits (1:35)
a. H. pylori infects and irritates the lining of the stomach.
b. Infection is acquired by the ingestion of foods and other substances contaminated with saliva, vomit, or feces from people harboring the bacteria in their stomach.
c. Rates of H. pylori infection are highest in countries with poor sanitary conditions.
C. Heartburn
1. Excessive production of stomach acid may also cause heartburn.
2. Heartburn is called that because acid from the stomach causes a burning sensation in the esophagus near the heart.
3. Stress, anxiety, and frequent use of aspirin, ibuprofen, naproxen appear related to ulcers and heartburn in some people.
4. Fatty foods, coffee, alcohol, citrus fruits, soft drinks, and other foods are involved.
5. Certain foods aggravate the symptoms of ulcers and heartburn.
6. High-fiber diets protect against development of ulcers and heartburn.
D. Irritable Bowel Syndrome
1. Irritable bowel syndrome (IBS) is a persistent disorder of the colon.
2. Colon (or bowel) in people with IBS spasms leading to painful cramps.
3. Gas production, bloat, diarrhea and constipation are common features of IBS.
4. Mild IBS treated with low fat diet, counseling and fiber, anti-diarrhea pills, and pain medications.
5. Serious IBS responds to stress reduction, eating in relaxed surroundings, anti-depressants, and drugs that reduce colon muscle spasms.
6. Probiotics, or “friendly” bacteria, help colonize the colon.
a. Friendly microorganisms help protect and heal the colon lining.
b. These are being increasingly used to treat IBS.
E. Diarrhea
1. Common in the United States, a leading public health problem in developing countries.
2. Most due to bacterial- or viral-contaminated food or water, lack of immunizations against infectious diseases, and vitamin A, zinc, and other nutrient deficiencies that make children particularly susceptible to diarrhea.
3. Diarrhea depletes the body of fluid and nutrients and produces malnutrition as well.
4. Severe diarrhea leads to dehydration, heart and kidney malfunction, and death.
a. 3.5 million deaths from diarrhea diseases occur each year to the world’s children five years of age or under.
5. Diarrhea can be prevented
a. Diarrhea prevented through food and water sanitation programs, immunizations, and adequate diets.
6. Oral rehydration fluids shorten the duration of diarrhea.
7. Foods such as yogurt, lactose-free or regular milk, chicken, potatoes and other vegetables, dried beans, and rice and other cereals provide nutrients needed for the repair of the intestinal tract.
8. Avoid sugary beverages, as these draw fluid into intestinal tract.
a. Do not increase the absorption of fluid.
F. Bacterial production of gas
1. Gas in the large intestine related to dried beans, broccoli, cauliflower, brussels sprouts, onions, corn, and other vegetables.
a. These contain complex carbohydrates that bacteria, not humans, break down.
b. Fructose and sorbitol lead to gas formation.
2. Bacteria produce gas as byproduct of carbohydrate digestion.
3. Heartburn, gastrointestinal tract disorders, and some medications associated with gas production.
G. Lactose maldigestion
v Instructor Resources: transparency #25: Lactose Maldigestion; Activity 7-5: Lactaid Milk
1. Lactose maldigestion is caused by genetically determined low production of enzyme that digests lactose.
2. People lacking this enzyme have free lactose in their large intestine after consuming milk or milk products containing lactose.
3. Lactose in the large intestine = lactose intolerance.
4. Symptoms include bloated feeling and diarrhea due to fluid accumulation, gas and abdominal cramping caused by excretion of gas by bacteria that digest lactose.
5. Milk
a. Milk solids, milk, and other lactose-containing components of milk may be added to foods you wouldn’t expect.
b. So it’s best to examine food ingredient labels.
c. Milk is a primary ingredient in sherbet.
d. Milk solids added to many types of candy.
6. Lactose Maldigestion for you?
a. Most reliable indicator of lactose maldigestion is lactose intolerance.
b. If you consistently experience these symptoms, visit your health care provider for a diagnosis.
c. Symptoms could be due to lactose, other substances in milk, or other problem.