ch 3: digestion and digestive disorders - nutrition

fluid mosaic model

a model of the cell membrane with hydrophilic head of phospholipids, proteins imbedded, and cholesterol in hydrophobic tails

• cholesterol: made by the liver and is in all animal products

• sugar side-chain may repel or attract certain nutrients

• diet: influences what can enter or leave the body

  • high sugar and ultra processed vs healthy diet — can see negative diff in cells bc they’re basically additives

• functions:

  • lets waste products leave

  • semi-permeable of what can enter

  • creates structure

  • signals pathways, impacts hormones

hypothalamus

where centers of feeding and satiety (fullness) are located in the brain

• nerve cells, hormones, amt of type of food influence satiety

• we all have different processes and varies from person to person

• satiety foods: cheeseburgers, pizza, fried chicken (fats and proteins: eggs and bacon)

hunger vs appetite

hunger: physiological need for food (hormones, stomach emptying)

appetite: psychological desire for food (smell, stress, environment)

• others:

  • digestion: breakdown of food into nutrients

  • craving: intense, specific urge for a particular food

signals

that prompt us to eat

• nerve receptors: from the stomach to the hypothalamus to indicate fullness/emptiness

• blood sugar levels:

  • low: signals hunger

  • rapid glucose spikes in those with diabetes causes intense hunger

• hormones: chemicals in specialized glands that travel thru the bloodstream to target organs

  • some hormones stimulate hunger and some produce feelings of satiety

  • on diet: genetics, stress, and amt of satiety hormones differ from person to person

• drugs

GI tract

has organs and sphincters (muscles) to control the passage of material from one organ to the next

• esophageal sphincter: separates esophagus from stomach at the top

• GERD (reflux disease): most common cause is obesity (apple: upper abdomen) and puts pressure on esophagus then weakens

• GI system: GI tract and accessory organs

• mouth: voluntary chewing/mechanical digestion, salivary amylase, minimal digestion

peristalsis

contracting of muscles to move food through the esophagus to the stomach

• involuntary

• no digestion occurs in esophagus

• bolus: chewed food with saliva (enzymes, mucus, water)

stomach

where peristaltic waves mix contents and starts mechanical digestion

• glands here secrete gastric juice: highly acidic fluid (pH1-3)

  • HCl, pepsin, mucus, gastric lipase, intrinsic factor for B12

  • converts food into a liquid mixture (chyme)

• gastrin: stimulates HCl secretion

• ghrelin: hunger hormone

• pepsin: protein digestion

• gastric lipase: lipid digestion

• small amounts of water, some minerals, drugs, and alc are absorbed

small intestine

main organ of absorption

• bile: alkaline fluid made by the liver and stored in the gallbladder

• pancreas: lipase/amylase/proteases digests fats/carbs/protein

  • bicarbonate: secreted by pancreas and neutralizes acidic chyme from stomach

• unable to absorb = deficiency and weight gain

absorption

in the small intestine

• villi and microvilli increase surface area

• digestive disorders: forms dead tissue and causes problems with weight gain and development

• capillary network: carries water soluble molecules — simple sugars, small molecules

• lacteal: fatty substances carried thru the body

• water soluble and fat soluble nutrients

water soluble

these nutrients (carb, protein, minerals, some vitamins) are absorbed in the small intestine

• carbs → monosaccharides

• proteins → amino acids

• fats → fatty acids + monoglycerides

• enter the portal vein: transports from GI tract, spleen, pancreas, and gallbladder to the liver

fat soluble

these nutrients (lipids and some vitamins) are absorbed in the small intestine

• enter the lymphatic vessels: absorbed by lacteal vessels from the small intestine to the bloodstream

elimination

undigested food moves through the ileocecal valve to the large intestine

• little digestion

• material stored 12-24 hrs then defecated

• water and some nutrients absorbed back into vessels and bloodstream

• made up of good bacteria

enzymes

amylase: break down carbs and starches into simple sugars

• produced in salivary glands (mouth) and the pancreas

protease: breaks down proteins into peptides and amino acids (pepsin in stomach)

• produced in the stomach, pancreas, and small intestine

lipase: break down fats (lipids) into fatty acids and glycerol

• produced in the pancreas, mouth, and stomach

hormones

ghrelin: stimulates hunger

• released by the stomach, small amts in SI and pancreas

leptin: signals satiety and suppresses appetite

• released by adipose tissue

gastrin: stimulates secretion of gastric acid (HCl) and promotes motility

• released in the stomach

CCK: stimulates bile release from gallbladder, promotes satiety

• released by small intestine

GLP-1: increases insulin secretion and decreases glucagon releases

• released by large intestine, promotes satiety

lactose intolerance

a digestive disorder caused by low lactase enzyme that digests lactose

• experience gas and bloating after consuming dairy

• caused by undigested lactose and is fermented by colonic bacteria

• helpful diet: dairy alternatives, lactose-free

celiac disease

a digestive disorder and autoimmune condition where you cant eat gluten

• a protein found in carb foods (ex: bread, grans)

• autoimmune condition: body attacks its own small intestine villi

  • will likely impair absorption of fat-soluble vitamins

• medical condition requires lab work

• ex: wheat, barley, salad dressing, condiments, snack foods, granola bars, cross-contamination

• symptoms: diarrhea, fatigue, weight loss

• gut looks flattened with no vili

• not that common

gut microbiome

where trillions of beneficial microorganisms in the gut help with proper digestion and absorption

• lots reside in GI tract to keep things moving

• vitamins and minerals properly absorbed

• stomach bug: bad bacteria getting thru digestive tract and make you sick (ex: eating something contaminated)

GERD

a digestive disorder that causes heart burn when susceptible to certain foods, and stomach acid falls back to esophagus

• sphincter between esophagus and stomach (lower esophageal sphincter) becomes weak or doesn’t relax right

• obesity, smoking, pregnancy, alcohol, acidic food/drinks

• ex: citrus, tomato-based, alcohol, coffee

• losing weight is a treatment

• drugs can manage acid

• helpful diet: low fat

allergies vs intolerance

allergies: trigger the body and immune system (full attack mode)

• 8 most common: dairy, shellfish, peanuts, eggs, wheat, fish, tree nuts, soy

• inflammatory response, carry epi pen

intolerance: non-immune, unpleasant symptoms in response to a food

• enzyme defciency

• ex: gives you diarrhea

irritable bowel syndrome

a digestive functional GI disorder with abnormal gut function but no sturctural damage

• stress and food sensitivities

• symptoms: abdominal pain, bloating, constipation

• nutrition strats: low-FODMAP diet, reduced caffeine, alcohol, high-fat foods, increase soluble fiber

diverticulosis

a digestive disorder in the large intestine that causes formation of sall pockets

• mainly impacts the older demographic (65+)

• doesn’t cause harm

• managed with high fiber diets

diverticulitis

a digestive disorder in the large intestine where 1+ pockets are infected

• caused by trapped fecal matter or bacterial infection

• treated by temporary liquid diet, high fiber diet, antibiotics (sometimes don’t work)

• or cut part of large intestine out, does not cause major damage

gastric ulcer

a digestive disorder with a open, painful sore in the inner lining of stomach caused by an infection of the bacteria H pylori

• stomach acidity increases

• can worsen by consuming excessive alcohol, caffeine, spicy foods

• grew out of control because of chronic stress/smoking/meds/imbalance of bacteria in the gut

• treated by resting, prescribing/changing meds, stop smoking

colon cancer

a digestive disorder with malignant growth of cells in the large intestine

• also caused by smoking, some genetics, and high diet in animal products

• infiltrates tissues and in the blood stream

• prevent by increasing fiber, exercise, and prevent waste products from sitting

• increasing fiber = insoluble fiber speeds intestinal transit time, and reduce exposure of colon cells to toxins

ulcerative colitis

a digestive disorder where there are inflamed ulcers exist in the innermost lining of colon

• exact cause is unknown

• can be worsened by sulfur-containing foods, processed foods, fructose/sugars, and dairy/gluten

crohn’s disease

a digestive disorder where there is inflammation throughout the digestive tract and large intestine (gut)

• can affect nutrient absorption

• flare up for certain foods

• eat anti-inflammatory foods such as fish and veggies

probiotics

live microorganisms that provide a health benefit when consumed in adequate amounts

• must survive food processing and digestion

• not all fermented foods

• ex: yogurt, granola, smoothies, juice

prebiotics

foods that feed beneficial gut bacteria

• nondigestible carbs (mostly fiber)

• High fiber foods that aren’t broken down by human digestive enzymes

• act as food for gut bacteria

• large intestine then fermented by gut bacteria

• ex: wheat, fruit, beans, grains