Digestive System & Aging- Chpt 10I. Functions:

A. Supply nutrients

B. Conversion to usable form

- mechanical, chemical digestion

C. Absorption

D. Elimination

E. Manufacturing, Storing Nutrients

II. Components of digestive system

A. Gastrointestinal tract (GI)

1. Mouth (+ oral cavity)

2. Pharynx

3. Esophagus

4. Stomach

5. Small intestine

6. Large intestine

B. Accessory structures:

1. Salivary glands

2. Liver

3. Gall bladder

4. Pancreas

5. Teeth

II. Aging of the GI tract

A. Generally well preserved into advanced age - interaction of medications, toxins, disease makes it difficult to discern - most common source of chronic discomfort in elderly ( diverticulosis, atrophic gastritis)- difficult to diagnose ( pain perception)

B. Oral region

1. Functions: Mastication, moistening food,taste, swallowing

2. Aging changes:

sensory neurons (taste, mouth feel)

aging taste perception (via smell) - reduced calorie intake

Slower healing of mucosa

Dysphagia (swallowing) 30-50%

C. Esophagus

1. Functions: move food to stomach via peristalsis, sphincters control

2. Age changes:

Motility (Auerbach plexus)

Gastric reflux (weakened lower sphincter)

3. Abnormal changes:rings/webs,

stricture (scar tissue), hiatal hernia

D. Stomach

1. Function: stretchable churning sac, pyloric sphincter controls chyme release into duodenum

some absorption of H2O, alcohol, medications

- HCl (highly acidic)

- secretes pepsin (protein), intrinsic factor (Vit B12 absorption)

2. “Normal”aging changes

* May be the most striking of GI tract

1. Reduced stomach mucosal lining

2. Reduced HCl secretion

3. Reduced intrinsic factor secretion

4. Some reduction in emptying rate

(136 vs 81 min for CHO meal)

Liquids more affected than solids

3. Abnormal changes

a. Atrophic gastritis - excessive thinning of mucosa

hypochlorhydria ( protein malabsorption)

B-12 absorption (pernicious anemia)

- autoimmune disease

? Linked to helicobacter pylori

B. peptic ulcers

- acid erodes wall of GI tract

gastric type in elderly

may be due to NSAID therapy (aspirin, Ibuprofen)

increased use of antacids, special diets

E. Small intestine

1. Functions:

- major site of digestion, absorption

of nutrients and water in GI tract

- secretes alkaline intestinal juice

- microvilli contain enzymes and increase surface area

2. Age changes

-little data available on mucosa

with gastritis see bacterial overgrowth in proximal part (compete with B vitamins, induce Ca+2, iron deficiencies)

- no change in intestinal motility

- decrease in lactase ( lactose intolerance)

- response to vit D Ca+2 absorption

- Vit A, K, zinc absorption

3. Abnormal changes

- peptic ulcer

increased by: excess caffeine,

stress, excess stomach acid

pain subsides after eatting

F. Large intestine

1. Functions:

- absorbs water,some electrolytes and vitamins

- propels fecal material to be emptied by rectum

defecation

2. Aging changes

- mucosal atrophy (mucus secreting)

- delay in transit time (more H2O absorbed)

- smooth muscle layer weakens

diverticulosis- structural change

constipation - functional change

( also influenced by exercise)

3. Abnormal changes

a. Diverticulitis - complication of diverticulosis (inflamed)

- prevented by dietary fiber

b. Fecal incontinence- inappropriate elimination, reduced control of external anal sphincter

(2nd leading cause of institutionalized)

CLASS ACTIVITY:

1. List 3 specific health habits you are going to change in your life (or suggest to a family member) that may affect the aging process

2. List all from the class and determine the “top 3”.

3. Be prepared to describe why it was chosen (i.e. the potential physiological effect of each)!

III. Age changes in accessory structures

A. Teeth

1. Function: Mastication

2. Aging changes:

-enamel staining, thinning

-weakened attachment to jaws

-gums recede (periodontal disease)

-edentulous ( all teeth lost) Normal?

B. Salivary glands: sublingual, parotid, submandibular

1. Function: Moisten food

2. Aging changes: function well-preserved in healthy elderly

- Reduced number of cells (1/3 less)

- Enzyme concentration (salivary amylase)

3. Abnormal changes

- Dry mouth in uncontrolled diabetes

(Xerostomia- 16-28%of elderly)

difficulty swallowing/speaking

discomfort

bad taste in mouth

increased risk for infection, periodontal disease, cavities

C. Liver

1. Digestive Function: produces bile

other vital functions:

- detoxify blood

- CHO, protein, lipid metabolism

- storage of iron, copper, Vit A,B12, D, E, K

-activate vitamin D

2. Normal aging

- little change in structure (some atrophy)

- blood flow, some cell alteration

- cytochrome 450 enzyme (metabolize drugs)

- incredible reserve capacity!

3. Abnormal changes in liver

a. Cirrhosis - top 10 cause of death

- scar tissue due to repeated damage (alcohol, bile duct blockage)

- malnourishment due to impaired absorption of fat and fat-soluble vitamins

- jaundice, bleeding, edema

PREVENTABLE!

D. Gall bladder

1. Function:sac beneath liver that stores and concentrates bile

- stimulated by CCK

2. Normal aging changes - relatively little

- CCK sensitivity (but small intestine makes more)

- wider bile duct but narrows near small intestine ( chance of stone trapped)

3. Abnormal changes

a. Gallstones

- 1/3 of abdominal surgeries in people over 70 yrs.

- concentrated bile (esp. older obese)

E. Pancreas

1. Function:

exocrine- secrete digestive enzymes (lipase, proteases, amylase) and alkaline “juice” via acinar cells

endocrine- secrete insulin, glucagon for glucose control

Islet of Langerhans

2. Aging changes

- slight overall changes

- reduced lactase in secretions (lactose intolerance)

- reduced insulin production and/or insulin resistance

- lower lipase (lipid absorption)

3. Abnormal changes

a. Pancreatitis - inflammation

- trauma, alcohol abuse, gallstone blocking duct

- can be life-threatening

- if endocrine cells injured (diabetes mellitus)

- exocrine cells--> fat, protein digestion

IV. Nutrition and aging (Chpt 11)

A. Animal models

- Calorie restriction increased lifespan

B. Relation to humans

- controversial

- optimal feeding needed during growth but avoidance of excessive body fat is advantageous

- limited data on lifelong dietary habits and longevity!

Epidemiological studies: High fruits/veggies associated with risk of stroke elderly men

No cause- effect established!

C. RDA for adults (p. 216)

1.estimate of nutrient needs of all healthy people

2. RDAs extrapolated from those aged 25-50

3. Many nutrients similar for young and elderly

Carbohydrate 55-60%of total calories

20-35 gms fiber

Protein .8 gram per kg (B wt.) per day

(1.5 gm/kg/d during intense training)

Fat < 30% of total calories

< 300 mg cholesterol

4. Limitations of RDAS

- heterogeneity in aged

- heavy use of prescription/over-the counter drugs

- presence of chronic disease

- physiologic changes with aging

5. Different RDAs for >70 yrs ????? LEVELs too HIGH: Magnesium Chromium

Vitamin A LEVELS too LOW: Protein

CalciumVitamin DriboflavinVitamin B-6Vitamin B-12

D. Problem nutrients for the elderly

1. Water deficiency- dehydration

- 70% in infants 50% elderly

- Most essential nutrient!

- blunted thirst mechanism, less efficient kidneys, use of diuretics, conscious restriction for incontinent

- minimum intake 1500 ml/day

2. Protein needs

- Nitrogen balance data hard to obtain

- is deficiency related to sarcopenia?

- Campbell suggested intke for elderly 1.0-1.25 g/kg per day

(25-56% over current RDA)

3. Vitamin deficiencies

a. B12 ( 3 ug for elderly)

b. Folate (linked to CHD) 200 ug

c. B6 (Pyroxidine) 1.9 mg/d

d. D 50 yr (400-600 IU)

> 70 yr (800 IU)

(Risk of toxic doses in supplements)

4. Minerals

a. Calcium deficiency- linked to osteoporosis

b. Sodium excess- linked to hypertension

Suggested Reading:

Nutrition in Aging, Eleanor Schlenker, WCB MCGraw-Hill, 3rd edition, 1998.

http://www.mhcollege.com