Human Nutrition Chapter 3

CHAPTER 3: 15/01/2020     The body’s cells o cells need oxygen, water and nutrients to do their work o genes determine nature of cells' work  affect how nutrients handled o cells organized into tissues o tissues from organs o organs can work together as body system transport of nutrients o body fluids supply tissues  blood (carries water soluble nutrients) goes from small intestine to liver to heart  lymph (carries fat-soluble nutrients) goes from the small intestine via the lymphatic system to the thoracic duct where lymph enters the bloodstream near the heart (mixing oil with water) o arteries carry oxygen and nutrients to the tissues o blood circulates among cells by capillaries  delivery of oxygen and nutrients  picks of carbon dioxide and waste o blood returns to heart via veins and carbon dioxide is removed by the lungs in exchange for oxygen o blood circulates to the kidneys where waste is removed, filtered by nephrons and excreted in the urine regulation o communication between organs and cells  hormones: insulin and glucagon regulate blood glucose  nervous system: responds to need for food (hunger) and regulated digestion (gastric juice)  hypothalamus monitors the availability of nutrients o combination of hormones and nervous system  fight or flight reaction: epinephrine (hormone) and body response/movements digestion o breakdown of nutrients into their smallest sub-units for absorption into the body  CHO —  Protein —  Fat — o mouth:  taste buds quite food acceptability  chew and mix food with saliva (mucus and enzymes) o esophagus  passes food to the stomach via peristalsis (wave-like muscular squeezing along digestive tract) o stomach  churns and mixes food to a liquid mass (chyme)  is 3 layers of muscle  movement of food controlled by  cardiac sphincter (into stomach)  pyloric valve (into small intestine)  adds hydrochloric acid, enzymes and fluid (gastric juice)  gastric juice is pH ~2  denatures protein  kills microorganisms  mucus protects the stomach wall look at pH of other things  heartburn: burning sensation in the chest caused by back flow of stomach acid into the esophagus  antacids for temporary heartburn belief o small intestine  major site of digestion  20 feet long  pancreas secretes bicarbonate that neutralized the acidic content from the stomach  enzymes from pancreas and small intestine digest CHO, protein and fat  pancreas — pancreatic duct — small intestine  bile emulsifies fat to assist digestion  bile is synthesized in the liver, stored in the gallbladder and enters small intestine via bile duct Absorption o movement of nutrients from small intestine into the blood (water-soluble nutrients) or lymph (fat-soluble nutrients) o large absorptive area created by folds of villi and smaller projections of microvilli o what is not absorbed, like fibre, stays in the large intestine and passes into the large intestine (colon) o lower gut:  reabsorbs water and minerals  passes waste (fibre, bacteria, any unabsorbed nutrients) and some water to rectum o rectum:  stores wastes (feces) prior to elimination Problems of the lower gut: o diarrhea  frequent, watery bowel movements  if severe and prolonged, leads to dehydration o constipation  infrequent, difficult bowel movements, often caused by diet, inactivity, dehydration or medication  change diet slowly, more fibre, water and physical activity      Storage systems: o body’s energy stores of excess energy-containing nutrients:  fat in fat cells/adipose tissue (large amount)  CHO as glycogen in liver and muscle (smaller amount)  other nutrient stores in other tissues like bone (Ca, P and other minerals) Controversy 3 — Alcohol o What is alcohol?  acts as lipid solvents  easily penetrate cells’ outer lipid membrane  Denature cell’s protein structure alcohol in alcoholic beverages = ethanol provides energy (7cal/g_ but is not a nutrient 12oz beer = 150cals; light beer = 100cals 3.5oz wine = 85-105 cals 1.5oz hard liquor = 105 cals (86 proof = 43% alcohol) 8oz soft drink = 100 cals o alcohol diffuses through the stomach wall into the bloodstream  food delays diffusion and stomach emptying  vomiting protests against high dose of toxin o alcohol absorbed rapidly in small intestine, regardless of food or not o physical effects:  increases urine output  mineral loss  slow drinker: alcohol collected by liver and processed  rapid drinker: some alcohol flows through rest of the body and brain Alcohol and the Brain: o a depressant o sedates nerve cells  judgment and reasoning  voluntary muscle control  respiration and heart action  “passing out” helps protect against consumption of lethal dose Alcohol and the Liver o liver detoxifies (metabolizes); major organ  80% alcohol dehydrogenase (ADH)  10% MEOS system (inducible)  10% excreted through breath and urine  blood alcohol is proportional to breath alcohol  females have less ADH in stomach o alcohol stimulates fat synthesis in the liver, both acutely and chronically o liver deterioration: fatty liver — fibrosis 9scar tissue) — cirrhosis (loss of function)           Alcohol and the body: o about 1.5h to metabolize 1 drink o walking, caffeine etc. do not detoxify o alcohol is preferentially used for energy, thus more fat is stored, especially in abdominal region o hangover: toxic effects of congeners (other substances in alcoholic beverages) o dehydration and rehydration of the brain o accumulation of formaldehyde  preferentially ethanol — acetaldehyde o toxic to cells and increases risk for diseases Longterm effects of alcohol o liver cells — amino acid metabolization o synthesis of blood lipids increases o toxic to muscles increased BP Dementia increase risk of cancer younger people: risk of death from any cause Alcohol and nutrition o alcohol abuse — malnutrition  inadequate food intake  impaired nutrient absorption and metabolism  thiamin deficiency  Wernicke-Korsakov syndrome o moderate alcohol use:  controversy regarding heart disease  moderate alcohol intake (1-2 drinks per day) may be beneficial for older people at increased risk  no benefit in recent study of 6000 men over 20 years  more than 22 drinks per week: increased death from all causes  more than 35 drinks per week: 2x mortality from stroke in men  health effects of wine:  high potassium in both wine and grape juice may lower high blood pressure  antioxidant proporties may protect against events that are thought to trigger heart disease  alcohol increases oxidations  dealcoholized wine, purple grape juice and grapes all contain similar phytochemicals  without potential dangers of alcohol o Alcohol and appetite  usually reduces appetite  in tense and elderly individuals, small doses of wine may improve appetite o o o o 