Transcript Digestive System & Aging- Chpt 10

Digestive System & Aging- Chpt 10
I. 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 (
malabsorption)
protein
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 wellpreserved 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/overthe 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
Calcium
Vitamin D
riboflavin
Vitamin B-6
Vitamin 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