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Genetic and environmental factors affecting taste preferences
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Children with heightened preference for sweet flavor and greater rejection of bitter flavors
May be a supertaster, taster, or nontaster
Ability to smell is needed to recognize flavors
Evidence in animal studies that taste preference is related to relevant mineral deficiency; may have implications for humans
•
Lambs choose feed high in calcium and phosphorus with deficient state (Villalba et al., 2008)
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Rats prefer potassium foods when deficient (Guenthner et al.,
2007)
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Hormonal impact on hunger and satiety affects quantities of food consumed
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Insulin promotes hunger
Cholecystokinin and leptin promote satiety
Chewing ability affects food choices
 Poor dental status or cleft lip affects ability to ingest foods
Ability to swallow
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Neurologic problems due to impaired neuromuscular strength/coordination affects ability to swallow various consistencies of foods/drinks —referred to as dysphagia
Achalasia (esophagus cannot relax to allow food into the stomach)
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Inability to swallow efficiently (generally the result of neurologic damage, as with premature birth, stroke, head injury, or neurodegeneration
Speech-language pathologist (SLP) evaluates swallowing ability; videofluoroscopy may be used with a barium swallow to observe transit of food through the esophagus and stomach
Thickened liquids are easier to swallow than thin liquids because of added control
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Solids:
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Mechanical soft (ground meats, soft foods)
Puree (all foods with solid consistency blenderized)
Liquids:
 Nectar thick (fluids need to be thickness of fruit nectars)
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Honey thick (all fluids are the thickness of honey)
Pudding thick (all fluids are the thickness of pudding)
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Digestion is the ingestion and breakdown of food matter through mechanical and chemical means to allow for intestinal absorption and cellular metabolism of energy
Digestion occurs with the macronutrients carbohydrate (CHO), protein (PRO), and fat (FAT)
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Mechanical: involves chewing of food into small particles to allow surface area for digestive enzymes and peristalsis, i.e., squeezing process of gastrointestinal tract that propels food through
GI
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Peristalsis can be impaired with neurologic damage
Gastroparesis : the condition when the stomach cannot mechanically move food into the intestines
Chemical: “hydrolysis” involves addition of water and use of digestive enzymes to chemically break down food particles
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Sources of enzymes —names usually end in
“ase”
Salivary amylase, or ptyalin (digests CHO)
Gastric pepsin (digests PRO) and lipase
(digests fats)
Intestinal & pancreatic: sucrase, lactase, maltase, trypsin (digests PRO), lipase (digests fats)
Bile is a substance that helps fat digestion through emulsification; acts like soap detergent
No digestion occurs in large intestines
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Occurs mainly in small intestines through the villi (microscopic hair-like projections)
Minerals are mainly absorbed in the duodenum
Glucose and water-soluble vitamins are mainly absorbed in the jejunum
Protein, fats, and fat-soluble vitamins are primarily absorbed in the ileum
Water & electrolytes are chiefly absorbed in the colon only, or large intestine
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Wall of the small intestine. (From Applegate EJ: The anatomy and physiology learning system , ed 3, Philadelphia, 2006, Saunders.)
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Monosaccharides do not require digestion
(glucose and fructose)
Digestion starts in the mouth with amylase
Disaccharides and starches continue to be broken down by pancreatic enzymes sucrase, lactase and maltase
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Fiber is mainly indigestible by humans; intestinal bacteria allow some digestion, with the bacteria giving off hydrogen and methane gases in the process, referred to as flatus
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Lactase deficiency is the most common digestive problem; inadequate lactase prevents the digestion of the disaccharide lactose into monosaccharides
Can be a temporary situation accompanying GI irritation, as with the
“stomach flu”
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Chemical digestion starts with HCL as well as protease digestive enzymes (AKA pepsin) in the stomach
Trypsin: digestive enzyme in the small intestine
Digested into peptides and then amino acids
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Digested into glycerol and fatty acids
Only finely emulsified fats begin digestion in the stomach via gastric lipase
Other fats require bile, as produced in the liver and stored in the gallbladder, for digestion
Continue to be broken down by lipase in the small intestine
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Needed for saliva and gastric secretions, helps with swallowing (avoidance of dehydration), used for body temperature control (fever increases need for kilocalories); needed for cellular metabolism with electrical conduction and other processes, allows loss of waste material, toxins
Found inside and outside of body cells, in blood and other body fluids
Need to ingest about 2 L daily (minimum 6 cups for adults); calculated needs generally 30 mL/kg body weight for adults —includes all substances liquid at room temperature
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Dehydration leads to hypernatremia (high blood sodium) that alters electrolyte balance and causes stress on the heart, affects sense of balance with increased risk of falls; severe dehydration causes renal failure
 Electrolytes are compounds that when dissolved in water allow for electric current to occur
Excess intake of water can leach minerals out of the system and lead to hyponatremia (low blood sodium level), with potential death from “water intoxication” resulting from cerebral edema
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Trace the digestion of a meal composed of a ham sandwich on whole-wheat bread, a glass of lowfat milk, and a fresh apple. Describe the mechanical and chemical processes that occur, and name the enzymes involved.
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Cellular nutrition
Krebs cycle occurs in the mitochondria of cells
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Uses O
2
“oxidation”
Releases CO
2
, H
2
O, energy (ATP)
Specific dynamic action of food
 The energy required to ingest (chew and transport), digest, and metabolize food nutrients
Hormones are required for metabolic processes
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Insulin is the only hormone that allows blood glucose to be used by the body cells
Thyroxine: produced from the amino acid tyrosine; contains iodine and has a major effect on the rate of metabolism
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Glucagon: primary hormone that works opposite of insulin to raise blood glucose levels via glycogenolysis (breakdown of glycogen stores of the liver and muscle)
Epinephrine (adrenalin): another counter-regulatory hormone (works counter to insulin); released in response to hypoglycemia (low blood glucose); increases metabolic rate
Cortisol: generally released along with epinephrine to correct hypoglycemia; also released with any form of stress
(physical or emotional)
Growth hormone: released, along with cortisol, at the time of waking and results in a natural rise in blood glucose at dawn; increases metabolic rate
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Amount of energy (kcal) required for basic processes of life
 Approximately 1200-1400 kcal for women
 Approximately 1600-1800 kcal for men
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Harris Benedict equation for BMR:
 Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x
 height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
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Dyspepsia: indigestion
Gastritis: inflammatory condition
Peptic ulcer: erosion of stomach lining; may be due to infection by Helicobacter pylori, and treated with antibiotics
Gastroesophageal reflux disease (GERD): simply known as heartburn
Dumping syndrome: when food suddenly leaves the stomach rapidly before stomach digestion is complete
Hiatal hernia: opening of the diaphragm allows the stomach to move up through it
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Sketch of hiatal hernia. (From Damjanov I: Pathology for the health professions , ed 3, St Louis, 2006, Saunders.)
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Malabsorption causing diarrhea; may be related to impaired digestion (e.g., antibiotic use destroys harmful and beneficial bacteria needed for digestion); replace beneficial bacteria with yogurt containing live bacterial cultures or buttermilk; lacking enzymes may be replaced (lactase and pancreatic tablets)
 Bariatric surgery that removes portions of the small intestinal tract will lead to malabsorption of nutrients
Irritable bowel syndrome (IBS): treated with increased soluble fiber as in psyllium seed
(Metamucil ™) or low fermentable CHO diet
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Constipation: corrected with increased fiber, fluids, and exercise
Crohn’s disease (regional enteritis): an inflammatory bowel disease; may benefit from bowel rest with provision of an elemental diet
Ulcerative colitis: another inflammatory condition of the large intestine; may benefit from consumption of fatty fish (omega-3 fats)
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Increased fiber helps prevent diverticulosis
Soluble fiber helps prevent worsening without adverse effects (tolerated with diverticulitis)
Mechanism by which low-fiber, low-bulk diets might generate diverticula. Where colon contents are bulky
(top), muscular contractions exert pressure longitudinally.
If lumen is smaller (bottom), contractions can produce occlusion and exert pressure against colon wall, which may produce diverticular ballooning.
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Food intolerances are not life threatening
Food intolerances cause discomfort but not anaphylactic shock
Food allergies are potentially life threatening with ingestion of the food item
Example:
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Lactose intolerance: low-lactose milk products are fine to try and are often tolerated (e.g., yogurt, cheese, lactose-reduced milk)
Milk protein allergy: No milk products (including cheese, yogurt, cream sauce, ice cream) because all contain protein and could lead to anaphylactic shock
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An immune response to protein with release of antibodies and histamine
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Immediate onset: most severe form; anaphylactic shock with risk of death due to suffocation
Delayed onset: disrupts quality of life; generally not life threatening
Common food allergens: milk, fish, shellfish, nuts, berries, egg white, chocolate, corn, wheat, pork, legumes and soy, citrus fruit
Testing: radioallergosorbent test (RAST blood test), skin pricks, elimination diet: no testing method infallible, but help to predict
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Genetic autoimmune condition, not a true allergy
Individuals with celiac need to avoid all traces of
 Wheat
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Oats (gluten free oats okay)
Barley
Rye
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Now recognized as one of the most common food intolerances in the world due to newer blood testing
Most common among persons with European heritage
Found with other autoimmune diseases (type 1 diabetes, Addison’s disease)
Villi of the small intestinal atrophy with ingestion of foods containing gluten (wheat/rye/barley), but regenerate with exclusion of all traces of gluten and the protein gliadin
Multiple nutrient deficiency can exist due to malabsorption from villi atrophy
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Conditions related to deficiencies of minerals, water-soluble vitamins, and protein due to damage to the duodenum and jejunum areas
 Poor growth and delayed puberty of children
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Iron-deficiency and other forms of anemia
Recurrent miscarriage and infertility
Osteoporosis
Irritable bowel syndrome may actually be celiac
Elevated liver enzymes (transaminases)
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Blood tests
 IgA TTG (antihuman tissue transglutaminase) and/or
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Intestinal biopsy
 Needed to confirm diagnosis with evidence of villous atrophy; if only antibodies are confirmed, may be due to early development of celiac
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Erosions of GI tract leading to impaired digestion and malabsorption
Altered appetite with reduced food intake, leading to malnutrition
Liver damage with impaired protein metabolism
Pancreatic damage causing reduced insulin production (a form of diabetes) and reduced ability to digest dietary fat
Wernicke-Korsakoff syndrome with deficiency of vitamin B
3 causing neurologic damage, psychosis, and dementia
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Increases cellular use of insulin
Raises HDL cholesterol (the “good” cholesterol)
Decreases tendency to form clots
Cautions with moderate alcohol intake:
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May lead to hypoglycemia for a person on insulin
Possible genetic link to alcoholism, preventing health care professionals from advising a person to start drinking alcohol in moderation
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
Vocabulary
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Dysphagia
Digestion
Absorption
Peristalsis
Gastroparesis
Intestinal microvilli
Lactose intolerance
Hyper/hyponatremia
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Specific dynamic action of food
Dyspepsia
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Gastritis
Peptic ulcer
Gastroesophageal reflux disease (GERD)
Dumping syndrome
Hiatal hernia
Ulcerative colitis
Crohn’s disease
Diverticulitis
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Factors affecting ingestion
Two forms of digestion
Know the basics of digestion/absorption for CHO, protein, and fat (slide 18 – i.e. where does digestion start? What is the end product of digestion? Where does absorption take place? What enzymes are involved? In addition to enzyme what is needed to help break fats down?)
Is fiber digested by humans?
Why is water important in digestion/absorption?
Where are water and electrolytes absorbed?
What is the relationship of hydration and sodium status?
What is the Krebs Cycle?
How do the following hormones affect blood sugar? Insulin, glucagon, cortisol
What grains need to be avoided in celiac disease?
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